Executive Summary

With two new major upgrades, the Heavy-flavor Tracker (HFT) and the Muon Telescope Detector (MTD), STAR Collaboration has positioned us well for leading the field in several major scientific programs in the next few years. We have maintained a similar pace in our scientific productivity and training of the next generation of young scientists for the last 15 years. To continue our excellent track record on science, we, the members of the STAR Collaboration, have recently produced a road map for our future in the form of our decadal plan, eSTAR Letter of Intent, Beam Energy Scan Phase II Whitepaper and are in the process of producing pp/pA document. This is a critical time for RHIC as a facility and STAR as a collaboration. STAR Collaboration is fully committed to our priorities based on the scientific pillars of studying QGP properties, quantifying nucleon spin structure, searching for critical point in QCD phase diagram and exploring the high-density gluon field in nuclei. A sustainable strong science program in STAR calls for realization of the proposed upgrades and substantial new initiatives, and require continuous effort and involvement from each and every collaborator. The STAR Collaboration proposes the following two-year beam-use request for RHIC run periods in year of 2015 and 2016, in order to achieve its near-term spin and relativistic heavy ion physics goals. A detailed breakdown of the proposed run periods is shown in Table.1.1.

Run 15:

 

The on-going run14 with Au+Au collisions at 200 GeV has been producing the first dataset with complete MTD and PIXEL/IST subdetectors of HFT. We have proposed a few incremental upgrades to the detectors, which are crucial components for a successful run15 scientific program. The necessary upgrades to the detectors are: refurbishing Forward Meson Spectrometer (FMS), a scintillator-based pre-shower detector in front of FMS, and Roman Pot Phase II*. These upgrades are anticipated to be ready for the run. The proposed run15 programs with p+p and p+Au collisions at Ös=200GeV provide crucial baseline measurements of charmed mesons and quarkonia. The same beam species will produce several important measurements to study the ridge phenomenon and onset of gluon saturation effect using the unique polarized p+Au collisions in a collider mode. 

 

A six-week run of p+p collisions at Ös=200GeV with longitudinal polarization will provide a data-set to further constrain the gluon polarization through inclusive jet and di-jet measurements at mid-rapidity, especially for large momentum fractions x, and constitutes the main spin physics objective for Run 15 longitudinal running. The non-zero gluon contributions to the spin structure of nucleon from double-longitudinal polarization measurement of dijet production have generated significant interests in further improving the measurements and its kinematic reach. The same run configuration also allows measures on A_LL of p⁰ in the forward meson spectrometer to reach significantly lower x kinematics.

 

We propose a subsequent six-week run of p+p collisions at Ös=200GeV with spins transverse to their momentum direction. These p+p collisions exhibit kinematic and dynamical effects that are directly sensitive to quark transversity and partonic motion within the proton. In addition to improving the existing measurements of IFF and Collins analyses, a refurbished FMS with additional pre-shower in the front will provide clean direct photon measurements in the forward rapidity. This program is complemented by studies of polarized p+p elastic scattering and central exclusive production, in which a far-forward proton is detected intact. The relocation of the Roman Pots allows concurrent data-taking with nominal beam configuration, and enables new measurements on A_N for exclusive J/Ψ production and inclusive diffractive production in p+p collisions.

 

A new program with five-week run with an integrated 300 nb^-1 luminosity of Ös_NN = 200 GeV p+Au collisions with transversely polarized proton beam is proposed to follow the 12-weeks of p+p collisions. The program will address important physics, such as gluon saturation, cold nuclear effects on open heavy flavor and heavy quarkonia production, the ridge effect in pA, the Cronin effect and the strangeness enhancement in small-size systems. Utilizing RHIC’s unique capability of polarizing the proton projectile beam on heavy nuclei, the ratio of single spin asymmetries in π⁰ and direct photon production at forward rapidity between p+A and p+p collisions can be used to provide access to the elusive nuclear Weizsaecker-Williams (WW) gluon distribution function. The asymmetry for exclusive J/Ψ production in ultra-peripheral p+A collisions measurable with the upgraded Roman-Pot detectors in STAR will explore the generalized parton distribution function E for gluons.

 

Run16:

 

We propose a 10-week run of Au+Au collisions at at Ö`s_NN = 200 GeV, integrating 10nb^-1 of luminosity with rare triggers for Upsilon states, gamma-jet correlation, Bà J/y and J/y production, and 2 billion minbias events for L_c and differential study of charm flow and correlations.

A total integrated luminosity of 20nb^-1 with the combination of run14 and run16 provides the necessary statistics for a measurement of three Upsilon states. We also request to collect 2 billion minimum-bias Au+Au collision events at Ö`s_NN = 200 GeV in Run16. The effective figure of merit in terms of statistics for the signal increases by about a factor of 6 for low p_T D0 in comparison to similar dataset taken in run14, t. This significant improvement will allow us to perform differential studies on the charmed hadron yields, flow and correlation in several centralities. More importantly, the high statistics and the improved pointing resolution for low momentum tracks will make the L_c measurement feasible (ct of L_c ~ 60 mm).

 

A 7-week run of transversely polarized p+p collisions at Ö`s_NN = 510 GeV with integrated luminosity of 700 pb^-1 is proposed for A_N fo W^± at mid-rapidity, g and exploratory DY measurements at forward rapidity. The possibility of measuring A_N for DY, W^+/-, Z⁰ Bosons and direct photons in one experiment would provide a unique world-class capability to test TMD evolution, access the Sivers function for sea quarks and test the prediction of non-universality for the Sivers function through three different processes to distinguish different underlying mechanisms.