Last two years of CMS physics study in Peking University 7/12/1997 Chinese-French Workshop, Beijing, 14-12-2006 Last two years of CMS physics study in Peking University .

CMS-PKU group Professor: Lecturer: Graduate students: Y. Ban Y. Mao 7/12/1997 Chinese-French Workshop, Beijing, 14-12-2006 CMS-PKU group Professor: Y. Ban Y. Mao S. Qian Lecturer: S. Wang Graduate students: Z. Yang L. Liu S. Guo . . . . Sijin QIAN CMS Physics study in Peking University

Outline Heavy Quarkonia production and polarization. Other works 7/12/1997 Chinese-French Workshop, Beijing, 14-12-2006 Outline Heavy Quarkonia production and polarization. Motivation. Event generation and simulation. Polarization parameter extraction: 2 methods. Other works CMS Analysis Note 2006/094 “J/y  m+m- Reconstruction in CMS” was approved. Suggestion on HLT J/y trigger Comparison between ORCA and CMSSW Ongoing work and the planned new physics topics Summary Sijin QIAN CMS Physics study in Peking University

Heavy Quarkonia production and polarization Chinese-French Workshop, Beijing, 14-12-2006 Heavy Quarkonia production and polarization Sijin QIAN CMS Physics study in Peking University

Motivation (1) Conventional Mechanism of Heavy Quarkonia: Chinese-French Workshop, Beijing, 14-12-2006 Motivation (1) Conventional Mechanism of Heavy Quarkonia: * parton interaction produces quark pair, quark pair bind into quarkonia. * color and spin is conserved during binding. The quarkonia is color-singlet, so the quark pair must be color-singlet too. -> Color Singlet Model (CSM) 1-2 orders of magnitude discrepancy between CSM prediction and CDF Result Prompt charmonium production Bottomonium production black dot: CDF experiment dashed line: color-singlet solid line : NRQCD fit J/Y： PRL, 79 (1997) 572  ： PRL, 88 (2001) 161802 Sijin QIAN CMS Physics study in Peking University

Motivation (2) New Mechanism of Heavy Quarkonia (COM): Chinese-French Workshop, Beijing, 14-12-2006 Motivation (2) New Mechanism of Heavy Quarkonia (COM): Parton interaction produces quark pair (ccbar), quark pair can be color-octet Quark pair can change color and spin through emitting gluon and then bind into quarkonia (J/psi, psi’...) -> Color Octet Mechanism (COM) Production of Quarkonia can be factored into 2 steps: Creation of the quark pair, can be color-singlet or color-octet Quark pair bind into quarkonia Short Distance Coefficient: Creation of quark-antiquark pair. This step is independent of final product. Can computed pertubatively Long Distance Matrix Element (LDME): How likely the quark pair will bind to the quarkonia. Sijin QIAN CMS Physics study in Peking University

Motivation (3) => Polarization puzzle NRQCD prediction Chinese-French Workshop, Beijing, 14-12-2006 Motivation (3) => Polarization puzzle NRQCD prediction PRL, 85(2000) 2886 a=+1: transversely polarized a=-1: longitudinally polarized CDF run 1 results q m+ m- J/Y direction in lab frame m+ direction in J/Y rest frame CDF run 2 results Sijin QIAN CMS Physics study in Peking University

Quarkonia polarization @ CMS Chinese-French Workshop, Beijing, 14-12-2006 Quarkonia polarization @ CMS Higher luminosity: better statistics in general especially important for ϒ which is expected to be described better by NRQCD Higher collision energy: larger cross-section higher pT region reached Better Muon Measurement preferable for J/Ψ → μ+μ− and ϒ → μ+μ− Sijin QIAN CMS Physics study in Peking University

Simulation of Heavy Quarkonia Chinese-French Workshop, Beijing, 14-12-2006 Simulation of Heavy Quarkonia PYTHIA 6.3.24 in CMKIN_6_0_0  include both CSM and COM Reproduce CDF Result  to confirm our understanding  to tune the NRQCD parameters Quarkonia simulation  keep the same NRQCD parameters and increase to LHC collision energy, 14TeV  FAMOS for CMS simulation Sijin QIAN CMS Physics study in Peking University

Reproduce CDF Result J/Y  * CTEQ5L PDF * √s =1800GeV Chinese-French Workshop, Beijing, 14-12-2006 Reproduce CDF Result J/Y  * √s =1800GeV * |y|<0.4 for  * CTEQ5L PDF * LDME from hep-ph/0106120 (J/Y) & PRD-63-094006 () * ||<0.6 for J/Y * 100k MC events Sijin QIAN CMS Physics study in Peking University

Chinese-French Workshop, Beijing, 14-12-2006 FAMOS Normalized 1fb-1 integral luminosity, the reconstructed J/y’s pT distribution may be like this : 1M MC events NRQCD parameters fitted from CDF Through FAMOS Enough statistics in first 1fb−1, 4 months’ run in 1032cm-2s-1 About 3000 events per GeV at pT=50GeV/c Sijin QIAN CMS Physics study in Peking University

Measurement of the polarization Chinese-French Workshop, Beijing, 14-12-2006 Measurement of the polarization Template fit: fit to a weighted sum of two MC templates: transverse polarization template and longitudinal polarization template. : fully transverse polarization : fully longitudinal polarization Sijin QIAN CMS Physics study in Peking University

Template fit Reconstruction efficiency a = -1 generation Chinese-French Workshop, Beijing, 14-12-2006 Template fit a = -1 generation a = +1 generation Reconstruction efficiency a=-1 reco template a=+1reco template Normalize to the same integral luminosity as signal events. Then fit with: To do the normalization we need to know the reconstruction efficiency, but the efficiency depends on a. So we first try a loop fitting. Sijin QIAN CMS Physics study in Peking University

Extraction Method (1): Loop Fit Chinese-French Workshop, Beijing, 14-12-2006 Extraction Method (1): Loop Fit Normalize to the MC templates a=0 efficiency Weighted efficiency Signal Pt distribution Weighted efficiency …… Solid Line is alpha input, data point is alpha fit value Sijin QIAN CMS Physics study in Peking University

Extraction Method (2): Neural Network Fit Chinese-French Workshop, Beijing, 14-12-2006 Extraction Method (2): Neural Network Fit deviation Neural network well fits input value. The result is not dependent on a and pT. These two methods can cross-check each other. Sijin QIAN CMS Physics study in Peking University

Differential cross-section Chinese-French Workshop, Beijing, 14-12-2006 Differential cross-section For each PT bin, the reconstruction efficiency can be calculated as a weighted sum of the efficiencies of the two MC template. The weight is from polarization fit. Sijin QIAN CMS Physics study in Peking University

Backgrounds B mesons’ decay include J/y ccbar→μμ x bbbar →μμ x Chinese-French Workshop, Beijing, 14-12-2006 Backgrounds B mesons’ decay include J/y ccbar→μμ x bbbar →μμ x General QCD, W+jets, Z+jets Minbias events The most important background is from B mesons’ decays. The last four backgrounds don’t have a peak on dimuon’s invariant mass. Sijin QIAN CMS Physics study in Peking University

Physics Letters B, Review of Particle Physics, Vol.592/1-4 (2004) 781. Chinese-French Workshop, Beijing, 14-12-2006 B production: B0 39.7±1.0% B+ B0s 10.7±1.1% b-baryon 9.9±1.7% BC － B decay branch ratio J/y + anything 1.16±0.10% Y(2S) + anything (4.8±2.4) ×10-3 Chi_c1 + anything 1.5±0.5% Physics Letters B, Review of Particle Physics, Vol.592/1-4 (2004) 781. Prompt J/psi events are the background for B meson physics, so we can learn much from B studies. The basic idea is to use the vertex cut. Sijin QIAN CMS Physics study in Peking University

Chinese-French Workshop, Beijing, 14-12-2006 Ongoing work and plan Re-do the study in CMSSW. Trigger influence study. Study the backgrounds, may learn from B physics groups. 1 Million full simulation events: Need much computing power and nearly 2T GB storage. By EUChinaGrid? Or to convince CMS to use higher version of Pythia? This may be one of the first CMS papers, if everything would go well. Sijin QIAN CMS Physics study in Peking University

Chinese-French Workshop, Beijing, 14-12-2006 Other Works Our first CMS AN 2006/094 “J/y  m+m- Reconstruction in CMS” was finally approved in last week Sijin QIAN CMS Physics study in Peking University

Chinese-French Workshop, Beijing, 14-12-2006 AN 2006/094 We analyzed the dataset bt03_B0sJPsiPhi at CNAF, which contains 198725 B0sJ/y(m+m- )f(K + K -) events. We focused on the J/y m+m- sub-process. J/y eff. vs pT Invariant mass J/y eff. vs Eta Sijin QIAN CMS Physics study in Peking University

L1 and HLT trigger rates Triggering rates L1 Trigger Chinese-French Workshop, Beijing, 14-12-2006 L1 and HLT trigger rates Triggering rates L1 Trigger L1 single muon bit 8.93% L1 double muon bit 33.7% L1 any muon bit 36.7% L1 decision 36.9% HLT Trigger Bit 35 HLTmuons: L3MuTrigger 0.20% Bit 38 double_muons: CombinatorialAndTrigger 0.44% HLT decision Bit 35 or 38 any muon was triggered 0.63% HLT global decision (cumulative after L1 and HLT) 0.66% Offline reconstruction Efficiency (i.e. offline) for events that pass HLT 68% Overall efficiency (L1*HLT*Offline) 0.45% =0.66%*68% Mass resolution (for J/y that passed HLT) 0.96% Sijin QIAN CMS Physics study in Peking University

Chinese-French Workshop, Beijing, 14-12-2006 Triggering effects PT distribution of the J/y h distribution of the J/y at different level: generator level, all reconstructed events without decision, L1 decision and HLT decision. Why HLT rejects high pT J/psi events? Sijin QIAN CMS Physics study in Peking University

HLT muon trigger has a bug in muon track isolation algorithm. Chinese-French Workshop, Beijing, 14-12-2006 HLT muon trigger has a bug in muon track isolation algorithm. DR distribution DR=0.24 Events passed HLT decision high J/psi PT (> 35 GeV/c) events Sijin QIAN CMS Physics study in Peking University

Chinese-French Workshop, Beijing, 14-12-2006 Tracker Isolation In order to isolate the muons from jets, which accompanied by nearby particles. It calculate the SpT of fully reconstructed tracks (charged particles) in a cone (DR=0.24) around the direction of the L3 muon, neglecting the contribution from the muon itself. If a high pT muon is reconstructed inside the cone around another muon, SpT will be very large, and the HLT isolation criteria will not be satisfied and the event will be rejected. So all the muon tracks in the cone should be neglected. This will be done in CMSSW. Sijin QIAN CMS Physics study in Peking University

Chinese-French Workshop, Beijing, 14-12-2006 Study on a possible HLT J/y trigger (was just reported in the CMS Standard Model meeting on this Monday) Sijin QIAN CMS Physics study in Peking University

Chinese-French Workshop, Beijing, 14-12-2006 HLT J/psi Trigger L2 Muon Producer L2 J/Psi Filter L3 Muon L3 J/Psi Filter The trigger may have two steps: one filter for L2 muons (stand-alone muons) and one for L3 muons (global muons). J/Psi filter: dimuon cuts on PT, Eta dimuon’s invariant mass window (2.0GeV, 4.2Gev) for L2 muons (3.0GeV, 3.2GeV) for L3 muons The PT cut should correspond to L1 muon trigger. Sijin QIAN CMS Physics study in Peking University

Trigger rates with different PT cuts Chinese-French Workshop, Beijing, 14-12-2006 Trigger rates with different PT cuts We both studied CSM and COM J/psi. Here: Luminosity = 1033 cm-2s-1 Cut (mass window) CSM (Hz) COM (Hz) L2 L3 Muon PT>3GeV/c (3.0GeV,3.2GeV) 2.57 2.20 34.1 28.8 Muon PT>4GeV/c 1.72 1.34 19.1 14.5 Muon PT>5GeV/c 0.998 0.872 8.93 7.61 Muon PT>6GeV/c 0.598 0.564 4.02 3.73 Muon PT>7GeV/c 0.401 0.383 1.82 1.77 Sijin QIAN CMS Physics study in Peking University

Possible trigger conditions at different luminosities Chinese-French Workshop, Beijing, 14-12-2006 Possible trigger conditions at different luminosities For Luminosity = 1029 cm-2s-1 L1 trigger may should be loose For Luminosity = 1030 cm-2s-1 L1 trigger For Luminosity = 1031 cm-2s-1 L1 trigger, PT cut 3GeV with mass window For Luminosity = 1032 cm-2s-1 L1 trigger, PT cut 5GeV with mass window For Luminosity = 1033 cm-2s-1 L1 trigger, PT cut 7GeV with mass window Sijin QIAN CMS Physics study in Peking University

Pay attention to the status of CMSSW muon reconstruction Chinese-French Workshop, Beijing, 14-12-2006 Pay attention to the status of CMSSW muon reconstruction Sijin QIAN CMS Physics study in Peking University

Comparing CMSSW with ORCA Chinese-French Workshop, Beijing, 14-12-2006 Comparing CMSSW with ORCA Stand-alone muons Genrated ORCA CMSSW_1_1_0 Muon PT J/y PT Muon Eta J/y Eta Sijin QIAN CMS Physics study in Peking University

J/y’s invariant mass CMSSW_1_1_0 ORCA Chinese-French Workshop, Beijing, 14-12-2006 J/y’s invariant mass CMSSW_1_1_0 ORCA ORCA implements Vertex-Update in stand-alone muon reconstruction, while CMSSW doesn’t. It will be implement soon. Sijin QIAN CMS Physics study in Peking University

Chinese-French Workshop, Beijing, 14-12-2006 Global muons In 1_1_0 to 1_2_0_pre8, there was a problem in MuonTrajectoryCleaner. So that the global muons are more than Stand-alone muons. It was fixed in CMSSW_1_2_0_pre9. But CMSSW_1_2_0_pre9 has some problems in stand-alone muons, only reconstruct half than CMSSW_1_1_0. Stand-alone muon Global muon Generated 4006 ORCA_8_13_3 3352 3194 CMSSW_1_1_0 3257 4186 CMSSW_1_2_0_pre2 3202 4011 CMSSW_1_2_0_pre9 1541 1346 We reported it last Sunday, and it was solved for 1_2_0 early this week. So we hope that we can use final CMSSW_1_2_0 to do some physics study. Sijin QIAN CMS Physics study in Peking University

Ongoing and future works Chinese-French Workshop, Beijing, 14-12-2006 Ongoing and future works More detailed study on the HLT J/y trigger in CMSSW. The HLT official production of 1 Million prompt J/y (still only CSM) will come out soon. The .cfg file is: Configuration/CSA06Production/data/Jpsi_mumu_sim_digi_OnSel.cfg Study on using J/y for calibration. Other physics topics (H  AA  4l, Top quark polarization and parity violation, etc.) Wish can collaborate with French colleagues for new topics Sijin QIAN CMS Physics study in Peking University

Thank you ! Chinese-French Workshop, Beijing, 14-12-2006 Sijin QIAN CMS Physics study in Peking University