June 2016
STAR Newsletter
June 2016 edition
Contents:- STAR at DIS 2016
- RHIC/AGS Users Meeting Re-cap
- From the Spokesperson
- Operations Activities
- News from Software & Computing
- Call for Summer Sunday Volunteers
A note from the editor: as a collaboration-wide communication tool, this newsletter is set up to allow comments (subject to moderation against abuse), and all STAR Collaborators are welcome to do so! Please keep in mind that some content (including all comments) may be considered internal to the Collaboration and only accessible when logged into Drupal. Documentation is available here.
STAR at DIS 2016
(Christopher Dilks - Student, PSU)
Bernd Surrow presented, on behalf of Devika Gunarathne, a measurement of the W+/- longitudinal single-spin asymmetry, AL, along with the cross section ratio RW=σW+/σW- from √s=510 GeV polarized proton collisions. This asymmetry is sensitive to the ratio of the up-antidown and down-antiup polarized PDFs, while RW helps constrain ratios of antiup and antidown PDFs. The W-boson analysis can also be used to help test the Sivers function sign-change, where the sign of the Sivers function in (SI)DIS processes differs from that in Drell-Yan or weak boson production. Salvatore Fazio presented the W-boson transverse single-spin asymmetry, AN from √s=500 GeV proton collisions. These data show a preference for fits which assume a Sivers sign-change over those which do not; more data will be taken in Run 17, which will also provide access to Drell-Yan processes via a postshower detector behind the FMS.
Another asymmetry, the longitudinal double-spin asymmetry, ALL, can be used in combination with current global fits in order to constrain one of the most interesting pieces of the spin puzzle, the gluon helicity distribution. Suvarna Ramachandran presented dijet ALL from √s=510 GeV proton collisions, as a function of dijet invariant mass; this measurement not only agrees with a prior 200 GeV measurement, but also improves constraints on the lower-x region of the gluon helicity distribution.
The remaining presentation on proton spin, by Christopher Dilks, was on data from Run 15. For the first time ever, polarized protons were collided against nuclei, in particular, gold and aluminum. Forward π0 transverse single-spin asymmetries from √s=200 GeV polarized p+p collisions were compared to those from p+Au collisions, and showed little difference. Implications and further studies from measurements from this dataset include tests on dependences on collision centrality, on nuclear mass number, and on nuclear modification factors.
Two presentations were given on the topic of UPCs: Spencer Klein presented an analysis of π+π- pairs from Au+Au collisions from Runs 10 and 11 and Bill Schmidke presented an analysis of J/ψ-mesons from the same dataset. Contributions to the π+π- invariant mass distribution include those from ρ0s, ωs, and direct π+π- photoproduction; all of these contributions agree with previous results. The high mass region of the π+π- spectrum also reveals a resonance consistent with the ρ3(1690). In discussing the J/ψ cross-section it was noted that although it is flat in rapidity, as expected, it is a factor of 2.5 times smaller than theory; more data is needed for a better comparison. Finally, transverse asymmetries of photo produced J/ψ-mesons are sensitive to gluon orbital angular momentum, which with the help of the Roman Pot detectors, will be analyzed in the near future along with those from next year's data.
Regarding the future of RHIC and the path toward the EIC, Elke Aschenauer presented motivation for moving toward polarized electron-proton collisions to complement RHIC's polarized p+p program. In the years leading up to the EIC, there are still many studies which can be performed at RHIC. More statistics on transversely polarized p+p collisions at √s=500 GeV will be collected next year, along with various detector upgrades such as those which could provide access to prompt photons or Drell-Yan signals. In later years, more statistics on p+A collisions are planned, along with more on √s=200 GeV transversely polarized p+p. Furthermore, a scan through A in polarized p+A collisions can be performed, which is a possibility unique to RHIC. With these data, questions about saturation, nuclear partonic structure, and attenuation and hadronization of colored quarks and gluons can be further studied. All of these measurements will complement those planned at an EIC.
RHIC/AGS Users Meeting Re-cap
(Lijuan Ruan - Meeting Organizer)
The annual RHIC/AGS Users' Meeting was held on June 7th-10th, 2016, at Brookhaven National Laboratory (BNL). The theme of this year's meeting was "RHIC Upgrades and the Era of Femtobarn-1 Precision." The meeting covered all aspects of the RHIC and eRHIC physics program. Particular emphasis was placed on the physics capabilities made possible by the detector upgrades coupled with RHIC II luminosities. Workshops were held on June 7th & 8th where heavy flavor and quarkonia, beam energy scan data, small systems, jets, chiral magnetic effects, spin, and diversity were discussed. In addition, a panel discussion on diversity was held on the evening of June 9th. It was the first time that we had a workshop and a panel discussion on diversity at our users' meeting, and it turned out to be a greatly successful event. Many thanks to the primary organizers Prof. Agnes Mocsy and Ph.D student Javier Koop for their tremendous efforts. A few distinguished social scientists and natural scientists in our field presented their views based on enormous data collected.
The plenary sessions on June 9th & 10th included talks on RHIC Run 16, the latest physics results from STAR and PHENIX, upgrade plans, reports from representatives from the funding agencies, and Thesis & Poster Award presentations. Plenary speakers from STAR included Rongrong Ma highlighting new heavy flavor results, Dan Cebra exploring the QCD phase diagram, Renee Fatemi covering spin & cold QCD topics, Paul Sorenson capturing collective dynamics, David Tlusty summarizing Run 16, and Rosi Reed detailing STAR upgrades.
Workshops
(Michael Lomnitz - Student, KSU,
Prithwish Tribedy - Research Assistant, BNL)
The first two days of the RHIC/AGS Users’ Meeting were set aside for workshops in different areas of interest. They provided a unique and more intimate environment for theoreticians and experimentalists from different collaborations to discuss fresh results and their interpretations.
In particular, the workshop on Heavy Flavor held during the first day of meetings was abuzz with excitement as both RHIC experiments have begun to let loose the first of many preliminary results obtained with dedicated upgrades intended to boost the measurements of open and hidden heavy flavor at top RHIC energy.
The STAR Experiment showcased results from both subsystems installed for 2014’s Run and at the heart of the heavy flavor program that ended this year. On one hand, the Muon Telescope Detector (MTD) sits outside of the STAR magnet and provides excellent triggering and particle identification for muons and is intended for reconstruction of hidden heavy flavor hadrons. Conversely, the Heavy Flavor Tracker (HFT) sits at the center of STAR and improves the experiment’s tracking resolution to distinguish particles from the collision vertex and those coming from secondary decays to reconstruct open heavy flavor. These two upgrades have proven successful and STAR members Michael Lomnitz and Qian Yang presented the first measurements J/ψ, D0, D+/- and Ds, which have already begun prompting discussions: Are charm quarks interacting strongly with the medium? Do they flow with it? Are we seeing evidence of J/ψ dissociation? While the jury may still be deliberating, the outlook is bright: with only a fraction of the Run 14 dataset processed and ~2 billion events collected during Run 16 we are looking forward to strong constraints from data and studying rare probes such Λc and Υ.
In the workshop on Chirality, Prithwish Tribedy and Liwen Wen showed the latest results on three particle correlations of inclusive and identified hadrons in searches for the Chiral Magnetic Effect (CME) and Chiral Vortical Effect (CVE) in Au+Au and U+U collisions. Results on the measurements of charge asymmetry dependence of kaon elliptic flow for the search of the Chiral Magnetic Wave (CMW were presented by Qi-Ye Shou. These latest results from STAR seem to challenge the background interpretation for the observables and show striking similarity with models that include the effects driven by a magnetic field. Observations of Lambda polarization were shown by STAR collaborator Isaac Upsal, which indicate the presence of vortical effects driven by non-zero angular momentum generated in non-central heavy-ion collisions.
The workshop on Jets was focused on the study of properties of QCD matter created in heavy-ion collisions using hard probes. Measurements on di-jet transverse momentum imbalance, hadron-triggered recoil jets, correlation measurements of direct-γ+hadron and π0+hadron in Au+Au with baseline measurements in p+p were discussed in detail in this workshop. Kolja Kauder gave an overview talk on the overall STAR jet results. These interesting results prove the versatility of the STAR Experiment in the direction of different jet measurements. An overview talk on RHIC measurements of jets was given by STAR collaborator Nihar Sahoo.
The workshop on Beam Energy Scan Physics included presentations from several members of the STAR Collaboration. The latest results on higher moments of multiplicity distributions in the search of a QCD critical point from STAR were presented in this workshop by Ji Xu. Measurements of the directed flow of several identified particles for the search of a 1st order phase transition were presented by Prashanth Shanmuganathan. Two dedicated presentations focused on the future upgrades of the STAR Experiment for the upcoming Beam Energy Scan II program and the unique fixed target program of STAR were presented by Bill Llope and Kathryn Meehan. And a talk on what we have learned from the low energy measurements of vn at RHIC was given by Paul Sorenson.
A Spin workshop was also held, featuring a couple STAR topics similar to what was discussed in the DIS 2016 section of this Newsletter. STAR speakers included Devika Gunarathne and Salvatore Fazio.
Posters
(Irakli Chakaberia - Research Assistant, BNL)
The third day of this year’s RHIC/AGS Users' Meeting was embellished by the poster session. To start with, it was well advertised, and students and postdocs were encouraged to submit their posters. The encouragement was supported by the cash prize incentive, which is always very much appreciated by both groups. The methods proved to be very fruitful and the session had a record number of posters this year. These 28 posters from various institutions and across all fields that take advantage of the RHIC facility were organized at the Lab’s Berkner Hall. Quite a few of these posters were from the STAR Experiment. The organization was at a very high level, with even poster pins provided for the participants.
The hall was ready to receive the poster-curious audience right on time, with the presenters standing guard by their brain products, some being the short summary of their doctorate theses. A couple posters were from the winners of the RHIC thesis award, the achievement proudly marked under their posters.
The poster labyrinth was conveniently located in the midst of the coffee and cookie tables luring attendants, while those enjoyed much needed caffeine reinforcement during the session breaks. Every now and then the awkward moment between the spectator and the host would last long enough for two to engage in a discussion about the presented topic and, in some cases, became very lively.
This year the title of the meeting was “RHIC Upgrades and the Era of Femtobarn-1 Precision”. Coincidently (or not), STAR's BNL group showcased an important ongoing upgrade of the STAR experiment in a poster on the overhaul of the inner sectors of the Time Projection Chamber (iTPC), by marketing the product under the title “The Brighter STAR”, to draw attention of the unsuspecting wondering eyes.
The rumor reached me that judges lurked around to assess the exhibits and reveal the one lucky winner of the prize, who would later similarly captivate the audience in a dedicated flash talk about the topic that emerged victorious.
On the next day, the results of the judging came at the end of the final plenary session and brought STAR an honorary mention thanks to Devika Gunarathne’s excellent study of a longitudinal single-spin asymmetry for W boson production in polarized p+p collisions. The main prize, though, went to Wenqing Fan for "Low pT Direct Photon Measurement in Different Collisions at √sNN=200 GeV".
At the end of the day, the posters vanished from the hall as seamlessly as they appeared, but hopefully the connections made during the meeting and, certainly the feelings left from the interesting discussions, met a different fate.
From the Spokesperson
(Zhangbu Xu - Spokesperson)
Dear STAR Collaborators:
It has been quite an exciting couple of months! RHIC has completed its Run 16 operation on June 27th. We have had another excellent year of data-taking, exceeding our goals of 2 billion HFT good 200 GeV Au+Au events, reaching over 90% of the MTD di-muon events, and accumulating more than 12 nb-1 of luminosity on γ-jet events. Meanwhile, we have achieved most of our goals from a mini-Beam-Energy-Scan of d+Au collisions at 200, 62.4, 39, and 19.6 GeV. This is the largest dataset in one Run so far, and a challenge for offline production with the available computing resources. I would like to acknowledge the efforts by the detector experts in preparing the subsystems to their best conditions, and operation experts in monitoring closely the detector performance, and collaborators taking shifts. Special appreciation goes to our five period coordinators with multiple weeks on duty: David Tlusty (Rice), Jochen Thaeder (LBL), Oleg Eyser (BNL), Takahito Todoroki (BNL), and Li Yi (Yale).
The eTOF group has completed and submitted a physics proposal to STAR management, and we are aiming to get all the support we need for a successful joint effort between the CBM and STAR collaborations. We have also reviewed two proposals: a post-shower detector for FMS, and the Event-Plane Detector (EPD). The committees recommended STAR to carry out these upgrades. Proposals and review reports are available here.
STAR has submitted our annual Beam Use Request on May 27th. The latest version of the BUR is available as a public STARNote. Details of the BUR committee and documentation are available here. I would like to thank the BUR committee and the collaborators who have made this possible.
We presented our cases to the BNL NPP Program Advisory Committee (PAC) on June 16th-17th. The agenda and materials of the PAC meeting are available online. A detailed PAC recommendation will be available next week. Verbal statements at the close-out session indicate that the PAC will endorse STAR's highest priority programs in Runs 17 & 18, and that the PAC is interested in the newly observed global hyperon polarization and is likely to endorse the 27 GeV Au+Au collisions proposed for Run 18. The PAC commented positively on the strong science cases developed for the CME, Cold QCD, and BES-II programs, and encouraged STAR to continue to quantify the performance impact of upgrades.
News from Software & Computing
(Jérôme Lauret - S&C Leader,
Gene Van Buren - S&C Co-Leader)
The STAR Software & Computing Team has continued to keep an eye on the future while working diligently on the datasets and resources of the present.
The ongoing production efforts highlighted in the last edition of this Newsletter have continued to progress well. The reproduction of Run 14 HFT data with the software bug fix is being extended beyond the 150M event sample to the full dataset. A reminder that our production data inventory page lists the dataset production progress (what has been produced and what not). Production is nowadays progressing at rate of ~15 TB of derived data per day, in parallel of data-taking, sometimes offering scalability challenges.
Run 16 has in fact recorded to tape an additional ~6B 200 GeV Au+Au events and over 2.5B d+Au events, filling ~7.7 PB of tapes as shown in the graph below.
As the Run is now done, we will need to prepare for several upgrades: the most significant will be the move to a new HPSS tape technology (LTO7 generation) in support of data-taking. This is of dire importance to STAR as during Run 16, and at a data acquisition rate around 1,600 MB/sec on average, we did not have enough tape drives to sustain the data production (priority is given to data writes). As a result, we suffered a slow down and could not saturate the available slot beyond an 80% level, purely due to resource starvation. Moving to LTO7 would mean that data acquisition would have its own drives and resources, while production would acquire all available drives.
Providing live access for analyses to the output of these ongoing productions along with numerous past year datasets of interest to Physics Working Groups requires storage capacities well beyond our existing resources. The 2014 Computing plan addendum was based on a constant $2.5M Equipment Budget per year which did not materialize. It already predicted the dire storage related situation we now have to face. Many discussions were carried with the PWGs on the possible adoption of the picoDST and JetTree (for Spin) formats. If STAR would be capable to reach a level where the sum of both would be less that the MuDST, this could very well bring a releif to the storage situation. The S&C team has helped PWGs understand the issues involved so that remediation approaches get their needed attention. Efforts and discussions have also included clean-up of non-critical datasets, and prioritization of what should be kept on live storage. At present, the STAR Data Management System will only restore what was declared as necessary (the rest will decay and eventually disappear). As an aside, S&C has engaged in a direct discussion with BNL management on the resource allocation at the RACF. The current farm occupancy monitoring graphs show a 97% saturation for STAR (with all downtimes understood to be infrastructure issues) while the PHENIX resources are only 87.5% utilized...and this over a period of a year.
The S&C team has also continued exploration of CPU resources at Dubna and NERSC. While the former is a continuation of multiple past efforts and expertise in utilizing Grid Computing, the latter represents a different vector through high performance computing (HPC) with the Cori supercomputer. These processing power scavenging efforts remain pertinent for STAR in the environment of a RHIC Computing Facility which has not grown as planned.
In mid-June, Jérôme visited our colleagues at LBNL/NERSC and was very pleased at the progress on many fronts. The NERSC/Cori exercise (with Mustafa Mustafa) is well on its way, the infrastructure related to Cataloging and possibly using using Xrootd at PDSF (with Jochen Thaeder) is converging, and the necessary infrastructure components to provide scalable and resilient services for STAR at NERSC are now in place including redundant container-based databases and the restoring of the regular maintenance of the OSG Gatekeeper for Grid operation purposes (as you may remember, we validate the libraries from BNL using the Grid interface and highly rely on it for data transfers). Jan Balewski, well known in STAR for his many achievements, is now employed by NERSC and cares for the support of STAR needs. A note that while Cori Phase-I is planned for decommisioning, this exercise has shown that STAR can indeed run on HPC resources within an MPI job and at a stunning 95% efficiency. This visit could not have been a whole success without the organization and attention from Jeff Porter, keeping a good eye on common needs. Many thanks to all involved for the welcome and the productive discussions.
With an eye towards long-range planning, a wokshop conducted by the DOE Office of Advanced Scientific Computing (ASCR) was carried recently. To review and map the mission critical objectives and needs over the next decade, at least one representative per community was invited. The workshop was very "science" and "use case" driven, asking for data size, rates, process of science, bandwidth, and the like. The high level summary "Quad Chart" for STAR is below (open the image in a new browser tab/window for higher resolution).
The full case study for STAR can be found at STARNote PSN068. The workshop went well but much work is still needed to ensure help is on the way - an interesting observation was that models seem to be evolving toward an Internet Of Things architecture, online or offline (depending on the experiments).
Last but not least, the long awaited integration of the CA seed/track finder is finally upon us. The first integration was achieved a few weeks ago (released as part of SL16f) and the final version will be part of the next library release. Summer is also the time where we release and integrate several projects (as there is no risk to disrupt Run support). Stay tuned for the announcements on our usual mailing lists.
Operations Activities
(Bill Christie - Operations Leader)
As I write this submission to the STAR Newsletter, RHIC Run 16 has ended. What was originally slated to be a 20 cryo-week Run was stretched to a final length of just over 23 weeks. Favorable rates for electric power through the early months of the Run enabled this extension.
Depending on how one looks at it, we had five different setups of the STAR detector for Run 16. The first setup was the timing and trigger setup for the initial 200 GeV Au+Au Run. This initial data set was scheduled for 10 weeks of running, but had a 19.5 day off time in the middle due to the failure of a diode in one of the RHIC Blue Ring dipole magnets (discussed in the last Newsletter). The days off were made up by adding 19.5 days to the original schedule plus an additional 2 days. After the setup for the four different d+Au energy data sets (discussed below) we came back to top energy Au+Au for the last ~8 days of Run 16. Given our status on reaching the various data set goals STAR had for the top energy Au+Au running, in those last 8 days we concentrated essentially all of the STAR bandwidth to bringing up the HFT minimum bias data set goal, which had only reached 75% of the 2B event goal when we stopped the early Au+Au running. To utilize the bandwidth most efficiently, we asked RHIC to lower our leveled luminosity by about 20% from where we had operated earlier, and removed the past and future protections from the HFT triggers. With some very good performance from both RHIC and STAR we managed to acquire about 300M events for the HFT in the last short period, and just passed the HFT minimum bias goal, ending with a total of 2.054B events! To see how we did on all the data set goals we'd set for the top energy Au+Au running please see the efficiency, trigger ratio, etc. plots that Jamie Dunlop generates (for each dataset in all of our Runs) here.
We ran four different d+Au energy data sets in Run 16, in the following order: 200 GeV, 62 GeV, 19.6 GeV, and 39 GeV. As a reminder, STAR had requested only the 19.6 and the 39 GeV data sets. As can also be seen from Jamie's data set tracking plots for these runs, we exceeded all of the goals we set for the 200 GeV d+Au, fell about 15% short of the goal we set for the 62 GeV, accumulated ~300% of the goal we set for 39 GeV, and achieved about 200% of our 20 GeV minimum bias goal.
All in all, another very challenging Run, but both STAR and RHIC did very well, and we accumulated an enormous amount of data (see the S&C contribution above).
The beam operations for RHIC Run 16 ceased on Monday morning June 27th just before 8 am. This was immediately followed by five shifts of cosmic ray data-taking, at zero field and without the TPC, for a final internal alignment calibration of the HFT systems. In parallel with this cosmic ray running, we got started on the STAR shutdown schedule.
The cosmic ray data effort ended about midnight on the next Tuesday night, and on Wednesday we extracted both the North and South halves of the PXL detector from STAR, and placed them into the Assembly Building clean room. Giacomo Contin had come out from LBNL earlier in the week, and by Thursday morning he'd removed the active detector heads from the PXL installation frames and boxed them for storage, as well as the electronics boards. We'll be finding places to store this PXL equipment in case it is decided to try and re-install and use it sometime after 2020.
The shutdown plan for STAR is fairly aggressive for the first month as we push to get STAR out into the Assembly Building prior to the annual RHIC open house for the public (see the next contribution). So far so good.
Call for Summer Sunday Volunteers
(Gene Van Buren - BNL)
Dear fellow STAR Collaborators:
Each summer, there is an Open House of the RHIC facility for the public. This is part of the BNL "Summer Sundays" tour program series that has open houses for various BNL facilities through the summer.
This year's RHIC Summer Sunday will take place on Sunday, July 31st. This is a call for volunteers that will or can be at BNL on that date, and would like to give tours of STAR or otherwise speak with the public. Many visitors are very appreciative of the chance to see and learn what goes on in these otherwise-closed facilities. In addition to the opportunity to explain to a diverse but interested audience what STAR & RHIC are and what we do, volunteers get a free "Polo" type cotton shirt with the BNL logo, as well as a free box lunch.
At the start of the day, we will review some talking points for the tours for first-time volunteers. So please do not feel that a lack of tour-giving experience should prevent you from participating.
The Lab admits people for these tours from 10 am in the morning until 3 pm in the afternoon. Out at STAR this means that we receive visitors from about 10:30 am until about 4:00 pm. We typically get on the order of 1000+ people who come through on these tours. To handle these crowds we usually try and have 8 to 10 tour guides present at STAR.
If you would like to volunteer to help with these tours (even if only for part of the day) please send me an email. Please include in such an email what shirt size you would like (e.g. S, M, L, XL; this year's color will be a rather dark red), as well as any preference you have for the box lunch sandwich (tuna, chicken, turkey, vegetarian, ham, or Italian). If you have any questions please feel free to contact me.
Please consider helping out with what can be a rewarding few hours of your time!
Workshops
(Michael Lomnitz - Student, KSU,
Prithwish Tribedy - Research Assistant, BNL)
The first two days of the RHIC/AGS Users’ Meeting were set aside for workshops in different areas of interest. They provided a unique and more intimate environment for theoreticians and experimentalists from different collaborations to discuss fresh results and their interpretations.
The STAR Experiment showcased results from both subsystems installed for 2014’s Run and at the heart of the heavy flavor program that ended this year. On one hand, the Muon Telescope Detector (MTD) sits outside of the STAR magnet and provides excellent triggering and particle identification for muons and is intended for reconstruction of hidden heavy flavor hadrons. Conversely, the Heavy Flavor Tracker (HFT) sits at the center of STAR and improves the experiment’s tracking resolution to distinguish particles from the collision vertex and those coming from secondary decays to reconstruct open heavy flavor. These two upgrades have proven successful and STAR members Michael Lomnitz and Qian Yang presented the first measurements J/ψ, D0, D+/- and Ds, which have already begun prompting discussions: Are charm quarks interacting strongly with the medium? Do they flow with it? Are we seeing evidence of J/ψ dissociation? While the jury may still be deliberating, the outlook is bright: with only a fraction of the Run 14 dataset processed and ~2 billion events collected during Run 16 we are looking forward to strong constraints from data and studying rare probes such Λc and Υ.
In the workshop on Chirality, Prithwish Tribedy and Liwen Wen showed the latest results on three particle correlations of inclusive and identified hadrons in searches for the Chiral Magnetic Effect (CME) and Chiral Vortical Effect (CVE) in Au+Au and U+U collisions. Results on the measurements of charge asymmetry dependence of kaon elliptic flow for the search of the Chiral Magnetic Wave (CMW were presented by Qi-Ye Shou. These latest results from STAR seem to challenge the background interpretation for the observables and show striking similarity with models that include the effects driven by a magnetic field. Observations of Lambda polarization were shown by STAR collaborator Isaac Upsal, which indicate the presence of vortical effects driven by non-zero angular momentum generated in non-central heavy-ion collisions.
The workshop on Jets was focused on the study of properties of QCD matter created in heavy-ion collisions using hard probes. Measurements on di-jet transverse momentum imbalance, hadron-triggered recoil jets, correlation measurements of direct-γ+hadron and π0+hadron in Au+Au with baseline measurements in p+p were discussed in detail in this workshop. Kolja Kauder gave an overview talk on the overall STAR jet results. These interesting results prove the versatility of the STAR Experiment in the direction of different jet measurements. An overview talk on RHIC measurements of jets was given by STAR collaborator Nihar Sahoo.
The workshop on Beam Energy Scan Physics included presentations from several members of the STAR Collaboration. The latest results on higher moments of multiplicity distributions in the search of a QCD critical point from STAR were presented in this workshop by Ji Xu. Measurements of the directed flow of several identified particles for the search of a 1st order phase transition were presented by Prashanth Shanmuganathan. Two dedicated presentations focused on the future upgrades of the STAR Experiment for the upcoming Beam Energy Scan II program and the unique fixed target program of STAR were presented by Bill Llope and Kathryn Meehan. And a talk on what we have learned from the low energy measurements of vn at RHIC was given by Paul Sorenson.
A Spin workshop was also held, featuring a couple STAR topics similar to what was discussed in the DIS 2016 section of this Newsletter. STAR speakers included Devika Gunarathne and Salvatore Fazio.
Posters
(Irakli Chakaberia - Research Assistant, BNL)
The third day of this year’s RHIC/AGS Users' Meeting was embellished by the poster session. To start with, it was well advertised, and students and postdocs were encouraged to submit their posters. The encouragement was supported by the cash prize incentive, which is always very much appreciated by both groups. The methods proved to be very fruitful and the session had a record number of posters this year. These 28 posters from various institutions and across all fields that take advantage of the RHIC facility were organized at the Lab’s Berkner Hall. Quite a few of these posters were from the STAR Experiment. The organization was at a very high level, with even poster pins provided for the participants.
The hall was ready to receive the poster-curious audience right on time, with the presenters standing guard by their brain products, some being the short summary of their doctorate theses. A couple posters were from the winners of the RHIC thesis award, the achievement proudly marked under their posters.
The poster labyrinth was conveniently located in the midst of the coffee and cookie tables luring attendants, while those enjoyed much needed caffeine reinforcement during the session breaks. Every now and then the awkward moment between the spectator and the host would last long enough for two to engage in a discussion about the presented topic and, in some cases, became very lively.
This year the title of the meeting was “RHIC Upgrades and the Era of Femtobarn-1 Precision”. Coincidently (or not), STAR's BNL group showcased an important ongoing upgrade of the STAR experiment in a poster on the overhaul of the inner sectors of the Time Projection Chamber (iTPC), by marketing the product under the title “The Brighter STAR”, to draw attention of the unsuspecting wondering eyes.
The rumor reached me that judges lurked around to assess the exhibits and reveal the one lucky winner of the prize, who would later similarly captivate the audience in a dedicated flash talk about the topic that emerged victorious.
On the next day, the results of the judging came at the end of the final plenary session and brought STAR an honorary mention thanks to Devika Gunarathne’s excellent study of a longitudinal single-spin asymmetry for W boson production in polarized p+p collisions. The main prize, though, went to Wenqing Fan for "Low pT Direct Photon Measurement in Different Collisions at √sNN=200 GeV".
At the end of the day, the posters vanished from the hall as seamlessly as they appeared, but hopefully the connections made during the meeting and, certainly the feelings left from the interesting discussions, met a different fate.
From the Spokesperson
(Zhangbu Xu - Spokesperson)
Dear STAR Collaborators:
It has been quite an exciting couple of months! RHIC has completed its Run 16 operation on June 27th. We have had another excellent year of data-taking, exceeding our goals of 2 billion HFT good 200 GeV Au+Au events, reaching over 90% of the MTD di-muon events, and accumulating more than 12 nb-1 of luminosity on γ-jet events. Meanwhile, we have achieved most of our goals from a mini-Beam-Energy-Scan of d+Au collisions at 200, 62.4, 39, and 19.6 GeV. This is the largest dataset in one Run so far, and a challenge for offline production with the available computing resources. I would like to acknowledge the efforts by the detector experts in preparing the subsystems to their best conditions, and operation experts in monitoring closely the detector performance, and collaborators taking shifts. Special appreciation goes to our five period coordinators with multiple weeks on duty: David Tlusty (Rice), Jochen Thaeder (LBL), Oleg Eyser (BNL), Takahito Todoroki (BNL), and Li Yi (Yale).
The eTOF group has completed and submitted a physics proposal to STAR management, and we are aiming to get all the support we need for a successful joint effort between the CBM and STAR collaborations. We have also reviewed two proposals: a post-shower detector for FMS, and the Event-Plane Detector (EPD). The committees recommended STAR to carry out these upgrades. Proposals and review reports are available here.
STAR has submitted our annual Beam Use Request on May 27th. The latest version of the BUR is available as a public STARNote. Details of the BUR committee and documentation are available here. I would like to thank the BUR committee and the collaborators who have made this possible.
We presented our cases to the BNL NPP Program Advisory Committee (PAC) on June 16th-17th. The agenda and materials of the PAC meeting are available online. A detailed PAC recommendation will be available next week. Verbal statements at the close-out session indicate that the PAC will endorse STAR's highest priority programs in Runs 17 & 18, and that the PAC is interested in the newly observed global hyperon polarization and is likely to endorse the 27 GeV Au+Au collisions proposed for Run 18. The PAC commented positively on the strong science cases developed for the CME, Cold QCD, and BES-II programs, and encouraged STAR to continue to quantify the performance impact of upgrades.
News from Software & Computing
(Jérôme Lauret - S&C Leader,
Gene Van Buren - S&C Co-Leader)
The STAR Software & Computing Team has continued to keep an eye on the future while working diligently on the datasets and resources of the present.
The ongoing production efforts highlighted in the last edition of this Newsletter have continued to progress well. The reproduction of Run 14 HFT data with the software bug fix is being extended beyond the 150M event sample to the full dataset. A reminder that our production data inventory page lists the dataset production progress (what has been produced and what not). Production is nowadays progressing at rate of ~15 TB of derived data per day, in parallel of data-taking, sometimes offering scalability challenges.
Run 16 has in fact recorded to tape an additional ~6B 200 GeV Au+Au events and over 2.5B d+Au events, filling ~7.7 PB of tapes as shown in the graph below.
Providing live access for analyses to the output of these ongoing productions along with numerous past year datasets of interest to Physics Working Groups requires storage capacities well beyond our existing resources. The 2014 Computing plan addendum was based on a constant $2.5M Equipment Budget per year which did not materialize. It already predicted the dire storage related situation we now have to face. Many discussions were carried with the PWGs on the possible adoption of the picoDST and JetTree (for Spin) formats. If STAR would be capable to reach a level where the sum of both would be less that the MuDST, this could very well bring a releif to the storage situation. The S&C team has helped PWGs understand the issues involved so that remediation approaches get their needed attention. Efforts and discussions have also included clean-up of non-critical datasets, and prioritization of what should be kept on live storage. At present, the STAR Data Management System will only restore what was declared as necessary (the rest will decay and eventually disappear). As an aside, S&C has engaged in a direct discussion with BNL management on the resource allocation at the RACF. The current farm occupancy monitoring graphs show a 97% saturation for STAR (with all downtimes understood to be infrastructure issues) while the PHENIX resources are only 87.5% utilized...and this over a period of a year.
The S&C team has also continued exploration of CPU resources at Dubna and NERSC. While the former is a continuation of multiple past efforts and expertise in utilizing Grid Computing, the latter represents a different vector through high performance computing (HPC) with the Cori supercomputer. These processing power scavenging efforts remain pertinent for STAR in the environment of a RHIC Computing Facility which has not grown as planned.
In mid-June, Jérôme visited our colleagues at LBNL/NERSC and was very pleased at the progress on many fronts. The NERSC/Cori exercise (with Mustafa Mustafa) is well on its way, the infrastructure related to Cataloging and possibly using using Xrootd at PDSF (with Jochen Thaeder) is converging, and the necessary infrastructure components to provide scalable and resilient services for STAR at NERSC are now in place including redundant container-based databases and the restoring of the regular maintenance of the OSG Gatekeeper for Grid operation purposes (as you may remember, we validate the libraries from BNL using the Grid interface and highly rely on it for data transfers). Jan Balewski, well known in STAR for his many achievements, is now employed by NERSC and cares for the support of STAR needs. A note that while Cori Phase-I is planned for decommisioning, this exercise has shown that STAR can indeed run on HPC resources within an MPI job and at a stunning 95% efficiency. This visit could not have been a whole success without the organization and attention from Jeff Porter, keeping a good eye on common needs. Many thanks to all involved for the welcome and the productive discussions.
With an eye towards long-range planning, a wokshop conducted by the DOE Office of Advanced Scientific Computing (ASCR) was carried recently. To review and map the mission critical objectives and needs over the next decade, at least one representative per community was invited. The workshop was very "science" and "use case" driven, asking for data size, rates, process of science, bandwidth, and the like. The high level summary "Quad Chart" for STAR is below (open the image in a new browser tab/window for higher resolution).
The full case study for STAR can be found at STARNote PSN068. The workshop went well but much work is still needed to ensure help is on the way - an interesting observation was that models seem to be evolving toward an Internet Of Things architecture, online or offline (depending on the experiments).
Last but not least, the long awaited integration of the CA seed/track finder is finally upon us. The first integration was achieved a few weeks ago (released as part of SL16f) and the final version will be part of the next library release. Summer is also the time where we release and integrate several projects (as there is no risk to disrupt Run support). Stay tuned for the announcements on our usual mailing lists.
Operations Activities
(Bill Christie - Operations Leader)
As I write this submission to the STAR Newsletter, RHIC Run 16 has ended. What was originally slated to be a 20 cryo-week Run was stretched to a final length of just over 23 weeks. Favorable rates for electric power through the early months of the Run enabled this extension.
Depending on how one looks at it, we had five different setups of the STAR detector for Run 16. The first setup was the timing and trigger setup for the initial 200 GeV Au+Au Run. This initial data set was scheduled for 10 weeks of running, but had a 19.5 day off time in the middle due to the failure of a diode in one of the RHIC Blue Ring dipole magnets (discussed in the last Newsletter). The days off were made up by adding 19.5 days to the original schedule plus an additional 2 days. After the setup for the four different d+Au energy data sets (discussed below) we came back to top energy Au+Au for the last ~8 days of Run 16. Given our status on reaching the various data set goals STAR had for the top energy Au+Au running, in those last 8 days we concentrated essentially all of the STAR bandwidth to bringing up the HFT minimum bias data set goal, which had only reached 75% of the 2B event goal when we stopped the early Au+Au running. To utilize the bandwidth most efficiently, we asked RHIC to lower our leveled luminosity by about 20% from where we had operated earlier, and removed the past and future protections from the HFT triggers. With some very good performance from both RHIC and STAR we managed to acquire about 300M events for the HFT in the last short period, and just passed the HFT minimum bias goal, ending with a total of 2.054B events! To see how we did on all the data set goals we'd set for the top energy Au+Au running please see the efficiency, trigger ratio, etc. plots that Jamie Dunlop generates (for each dataset in all of our Runs) here.
We ran four different d+Au energy data sets in Run 16, in the following order: 200 GeV, 62 GeV, 19.6 GeV, and 39 GeV. As a reminder, STAR had requested only the 19.6 and the 39 GeV data sets. As can also be seen from Jamie's data set tracking plots for these runs, we exceeded all of the goals we set for the 200 GeV d+Au, fell about 15% short of the goal we set for the 62 GeV, accumulated ~300% of the goal we set for 39 GeV, and achieved about 200% of our 20 GeV minimum bias goal.
All in all, another very challenging Run, but both STAR and RHIC did very well, and we accumulated an enormous amount of data (see the S&C contribution above).
The beam operations for RHIC Run 16 ceased on Monday morning June 27th just before 8 am. This was immediately followed by five shifts of cosmic ray data-taking, at zero field and without the TPC, for a final internal alignment calibration of the HFT systems. In parallel with this cosmic ray running, we got started on the STAR shutdown schedule.
The cosmic ray data effort ended about midnight on the next Tuesday night, and on Wednesday we extracted both the North and South halves of the PXL detector from STAR, and placed them into the Assembly Building clean room. Giacomo Contin had come out from LBNL earlier in the week, and by Thursday morning he'd removed the active detector heads from the PXL installation frames and boxed them for storage, as well as the electronics boards. We'll be finding places to store this PXL equipment in case it is decided to try and re-install and use it sometime after 2020.
The shutdown plan for STAR is fairly aggressive for the first month as we push to get STAR out into the Assembly Building prior to the annual RHIC open house for the public (see the next contribution). So far so good.
Call for Summer Sunday Volunteers
(Gene Van Buren - BNL)
Each summer, there is an Open House of the RHIC facility for the public. This is part of the BNL "Summer Sundays" tour program series that has open houses for various BNL facilities through the summer.
This year's RHIC Summer Sunday will take place on Sunday, July 31st. This is a call for volunteers that will or can be at BNL on that date, and would like to give tours of STAR or otherwise speak with the public. Many visitors are very appreciative of the chance to see and learn what goes on in these otherwise-closed facilities. In addition to the opportunity to explain to a diverse but interested audience what STAR & RHIC are and what we do, volunteers get a free "Polo" type cotton shirt with the BNL logo, as well as a free box lunch.
At the start of the day, we will review some talking points for the tours for first-time volunteers. So please do not feel that a lack of tour-giving experience should prevent you from participating.
The Lab admits people for these tours from 10 am in the morning until 3 pm in the afternoon. Out at STAR this means that we receive visitors from about 10:30 am until about 4:00 pm. We typically get on the order of 1000+ people who come through on these tours. To handle these crowds we usually try and have 8 to 10 tour guides present at STAR.
If you would like to volunteer to help with these tours (even if only for part of the day) please send me an email. Please include in such an email what shirt size you would like (e.g. S, M, L, XL; this year's color will be a rather dark red), as well as any preference you have for the box lunch sandwich (tuna, chicken, turkey, vegetarian, ham, or Italian). If you have any questions please feel free to contact me.
Please consider helping out with what can be a rewarding few hours of your time!
Previous Edition: April 2016
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