# 2009 Lambda D_LL @ 200 GeV

Presentations:

Run QA by Qinghua Xu (SDU)

# 1) Preliminary results

Preliminary released on SPIN 2012 and DNP 2012.

Presentation @ SPIN 2012 by Jian Deng (SDU)
Presentation @ DNP 2012 by Ramon Cendejas (UCLA)

# 2) Lambda reconstruction

1. Cuts setup:
 lam_pt dac2 dcaV0 dca_p dca_pi nsigma dlength cosrp jet_det_eta jet_Rt jet_dr 2,3 <0.7 <1.2 >0.2 (0.4,30) <3 (3,130) >0.98 (-0.7,0.7) (0.01,0.94) <0.7 3,4 <0.5 <1.2 0 (0.4,30) <3 (3.5,130) >0.98 (-0.7,0.7) (0.01,0.94) <0.7 4,5 <0.5 <1.2 0 (0.4,30) <3 (4,130) >0.98 (-0.7,0.7) (0.01,0.94) <0.7 5,8 <0.5 <1.2 0 (0.4,30) <3 (4.5,130) >0.98 (-0.7,0.7) (0.01,0.94) <0.7

2. Analysis plots:

cos\theta^* vs mass by pT .pdf
slope band from K0-short: .pdf

3. Invariant Mass distribution and background estimation, side band vs. fitting

All 4 lambda pT bins, fired jet only .pdf .txt no fired jet required .pdf .txt

4. Extract Lambda and Anti-Lambda yields for 20 cos \theta^* , for 4 spin status, for JP1 and L2JetHigh triggers.
 Lambda pT Lambda JP1 AntiLambda JP1 Lambda L2JetHigh AntiLambda L2JetHigh 2, 3 FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html 3, 4 FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html 4, 5 FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html 5, 8 FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html

5. Extract DLL from the spin sorted Lambda/AntiLambda yeilds in each cos \theta^* bin, for each trigger
 Lambda pT Lambda JP1 AntiLambda JP1 Lambda L2JetHigh AntiLambda L2JetHigh 2, 3 FiredJet .html  noFire .html FiredJet .html  noFire .html FiredJet .html  noFire .html FiredJet .html  noFire .html 3, 4 FiredJet .html  noFire .html FiredJet .html  noFire .html FiredJet .html  noFire .html FiredJet .html  noFire .html 4, 5 FiredJet .html  noFire .html FiredJet .html  noFire .html FiredJet .html  noFire .html FiredJet .html  noFire .html 5, 8 FiredJet .html  noFire .html FiredJet .html  noFire .html FiredJet .html  noFire .html FiredJet .html  noFire .html

6. Fit DLL vs. cos \theta^* to extract the "DLL"

 Lambda pT Lambda JP1 AntiLambda JP1 Lambda L2JetHigh AntiLambda L2JetHigh 2, 3 FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html 3, 4 FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html 4, 5 FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html 5, 8 FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html FiredJet.pdf .txt .html  noFire .pdf .txt .html

7. DLL correction

Appendix,  Anti-Lambda/Lambda ratio:

# 3) New simulation production

Background
Simulations performed by Ramon Cendejas. Unfortunately, an error was found in the (subdominant) process contributions when Ramon needed to move on. This and other factors held up progress since.

Introduction
• Pure MC simulation under STAR geometry.
• Generate pp events using Pythia 6.4.28 (Tune 320) with Lambda filter, in different partonic pT intervals and weighted by integral luminosities
• Reconstruct Lambda based on track association
• Jet reconstruction used CDF cone algorithm with R = 0.7

Statistics of simulation sample
It totally took about 4.5 CPU years.

Slides20170110

Jet Cone Study
1. slides (JP1 lambda pt2-3 for example)
2. All comparison plots for different lambda pt bin and different Triggers

Trigger Bias Plot
1. updated version for cdf cone algorigthm

Data/MC comparison for
Lambda:

 lamdba pt JP1 L2JetHigh 2_3 file file 3_4 file file 4_5 file file 5_8 file file
Anti-lambda:
 A-lamdba pt JP1 L2JetHigh 2_3 file file 3_4 file file 4_5 file file 5_8 file file

QA:
 lamdba pt MB JP1 L2JetHigh 2_3 file file file 3_4 file file file 4_5 file file file 5_8 file file file

Trigger effect: (old, anti-kt R06 )
 f_z feed down parton subprocess Lambda file1 file2 file file file A-lambda file1 file2 file file file

# 4) Systematic uncertainties

Systematic uncertainties summary

• decay, fz, and f_parton from simulation
• pile-up and residual background are from preliminary version

 η > 0 η < 0 Lambda Anti-lambda Lambda Anti-lambda pt JP1 L2J JP1 L2J JP1 L2J JP1 L2J decay 2.4 0.0009 0.0018 0.0001 0.0003 0.0001 0 0.0001 0.0001 3.4 0.0008 0.0011 0.0004 0.0003 0 0.0001 0 0 4.4 0.002 0.0027 0.0008 0.0008 0.0003 0.0004 0.0001 0.0002 5.9 0.0017 0.0024 0.0013 0.0022 0.0005 0.0009 0.0003 0.0007 fz 2.4 0.0011 0.0028 0.0003 0.0015 0.0002 0.0001 0.0001 0.0001 3.4 0.001 0.0034 0.0006 0.0024 0.0003 0.0005 0.0003 0 4.4 0.0056 0.008 0.0053 0.0079 0.0005 0.0007 0.0009 0.0013 5.9 0.009 0.0121 0.0154 0.0191 0.0021 0.0028 0.0037 0.0046 fparton 2.4 0.0005 0.0008 0.0004 0.0012 0.0001 0.0001 0.0001 0.0002 3.4 0.0011 0.0021 0.0002 0.0013 0.0003 0.0005 0 0.0003 4.4 0.0019 0.0038 0.0003 0.0011 0.0005 0.0009 0.0001 0.0003 5.9 0.0034 0.0062 0.0016 0.0027 0.0011 0.002 0.0005 0.0009 pile-up 2.4 0.0182 0.0057 0.0184 0.0063 0.0182 0.0057 0.0184 0.0063 3.4 0.0023 0.0007 0.0022 0.001 0.0023 0.0007 0.0022 0.001 4.4 0.0023 0.0007 0.0022 0.001 0.0023 0.0007 0.0022 0.001 5.9 0.0068 0.0023 0.0064 0.0023 0.0068 0.0023 0.0064 0.0023 bkgd 2.4 0.005 0.001 0.0001 0.0002 0.005 0.001 0.0001 0.0002 3.4 1.00E-06 0.0001 0.0001 0.0006 1.00E-06 0.0001 0.0001 0.0006 4.4 0.0007 4.00E-05 0.0004 0.0002 0.0007 4.00E-05 0.0004 0.0002 5.9 0.0002 0.0002 0.001 0.0001 0.0002 0.0002 0.001 0.0001 all 2.4 0.0189 0.0067 0.0184 0.0066 0.0189 0.0058 0.0184 0.0063 3.4 0.0029 0.0042 0.0023 0.0030 0.0023 0.0010 0.0022 0.0012 4.4 0.0067 0.0093 0.0058 0.0081 0.0025 0.0014 0.0024 0.0017 5.9 0.0119 0.0140 0.0168 0.0196 0.0072 0.0042 0.0075 0.0053

# 5) Paper proposal

Title:
Improved measurement of the longitudinal spin transfer to $\Lambda$ and $\bar{\Lambda}$
hyperons in polarized proton-proton collisions at $\sqrt{ s}$ = 200 GeV at RHIC

PAs:

Ramon Cendejas, Jian Deng, Jincheng Mei, Ernst Sichtermann, Qinghua Xu, and Jinlong Zhang

Proposed Target Journal:
PRD

Abstract:

The longitudinal spin transfer $D_{LL}$ of $\Lambda$ and $\bar{\Lambda}$ hyperons is expected to be sensitive to the helicity distribution function of strange quarks and anti-quarks, and to the longitudinally polarized fragmentation functions. We report an improved measurement on the longitudinal spin transfer of $\Lambda$ and $\bar{\Lambda}$ hyperons in proton-proton collisions at $\sqrt{s}$ = 200 GeV with the STAR detector at RHIC. The data are based on an approximately twelve times larger than that for our previously reported measurement and cover a kinematic range of $|\eta|<$ 1.2 in pseudo-rapidity and cover transverse momentum $p_T$ up to 6 GeV/c.  The dependences on $\eta$ and $p_T$ are presented and compared with model evaluations.

Figures:

Fig.1

Caption:
a) The invariant mass distribution for $\Lambda$ (red filled circles) and $\bar{\Lambda}$ (blue open circles) candidates with 3 $< p_T <$ 4 GeV/c in this analysis and b) the corresponding distribution versus the hyperon rest-frame angle $cos\theta^*$.

Fig.2

Caption:
The raw spin transfer $D _{LL}^{raw}$ versus cos for a) $\Lambda$ and b) $\bar{\Lambda}$ hyperons, and c) the spin asymmetry $\epsilon_{LL}$ for the control sample of $K_S^0$ mesons versus cos/theta  in the $p_T$ bin of (3,4) GeV/c for JP1 triggered sample. The red filled circles show the results for positive pseudorapidity $\eta$ with respect to the polarized beam and the blue open circles show the results for negative $\eta$. Only statistical uncertainties are shown.

Fig.3

Caption:
Comparison of spin transfer $D_{LL}$ for  for positive and negative $\eta$ versus $p_T$ for differently triggered samples in the present analysis, together with previously published results in the region of kinematic overlap. The results obtained with the L2JetHigh trigger have been offset to slightly larger $p_T$ values for clarity. The published results have been offset to slightly smaller $p_T$ values.

Fig.4

Caption:  Comparison of  spin transfer $D_{LL}$ with model predictions for positive $\eta$ versus $p_T$. The vertical bars and boxes indicate the sizes of the statistical and systematic uncertainties, respectively. The $\bar{\Lambda}$ results have been offset to slightly larger pT values for clarity.

Tables:
Tab 1

Caption: Summary of the selection cuts for \lla\ reconstruction for run9 Jet-Patch triggered sample and the corresponding $\Lambda$ ($\bar{\Lambda}$) counts and background fraction . Here DCA'' denotes distance of closest approach'' (to the primary vertex for single track by default) , and $\vec r$ denotes the vector from primary vertex to the V0 vertex and $\vec p$ denotes the momentum vector of V0.

Conclusion:

In summary, we report an improved measurement of the longitudinal spin transfer, $D_{LL}$, to $\Lambda$ hyperons and $\bar{\Lambda}$ anti-hyperons in longitudinally polarized proton-proton collisions at $\sqrt{s}$ = 200 GeV.  The data correspond to 19 pb$^{-1}$ with an average beam polarization of 57\% and were obtained with the STAR experiment in the year 2009.  The data cover -1.2 $<\eta<$ 1.2 and $p_T$ up to 6 GeV/c.  The longitudinal spin transfer is found to be $D_{LL}$ = -0.036 $\pm$ 0.048 (stat) $\pm$ 0.014(sys) for $\Lambda$ hyperons and $D_{LL}$ = 0.032 $\pm$ 0.043(stat) $\pm$ 0.019 (sys) for $\bar{\Lambda}$ anti-hyperons produced with $<$$\eta$$>$ = 0.5 and $<$$p_T$$>$ = 5.9 GeV/c.  While the data do not provide conclusive evidence for a spin transfer signal, the data tend to be below a model evaluation (DSV seen. 3) based on the extreme assumption that the quark polarized fragmentation functions are flavor-independent.

Paper draft and review:

Previous Publication:

Run 2005 DLL (PRD(R)) (comparison between run 9 and published run 5 data  points .pdf

Documentation:

Presentations:

• Preliminary result release at SPIN2012, DNP2013 (comparison between preliminary and final results .png)
• Nov 10, 2016 Analysis Meeting @LBL (link)
• May 16, 2017 Collaboration Meeting @BNL (link)
• Nov 10, 2017 PWGC review (link) (significance)
• Jan 25, 2018 Collaboration Meeting @LBL (link)

Analysis Note and Thesis:

Analysis Code:

• Code in Protected Area: link