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Prospect of Studying Direct J/ Ψ Production with ATLAS at the LHC.

Prospect of Studying Direct J/ Ψ Production with ATLAS at the LHC. E.Etzion, J. Ginzburg Tel Aviv University 4 th International Workshop on Heavy Quarkonia Brookhaven National Laboratory, 27-30 June 2006. Outline. 1. Heavy Quarkonia Production at the LHC. 2. ATLAS.

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Prospect of Studying Direct J/ Ψ Production with ATLAS at the LHC.

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  1. Prospect of Studying Direct J/Ψ Production with ATLAS at the LHC. E.Etzion, J. Ginzburg Tel Aviv University 4th International Workshop on Heavy Quarkonia Brookhaven National Laboratory, 27-30 June 2006

  2. Outline 1. Heavy Quarkonia Production at the LHC 2. ATLAS 3. Generation with Pythia (NEW features!) 4. J/Psi selection 5. Polarization Measurement 7. Prospect Heavy Quarkonia 2006

  3. s = 14 TeV(7 times higher than Tevatron/Fermilab) •  search for new massive particles up to m ~ 5 TeV • Ldesign = 1034 cm-2 s-1 (>102 higher than Tevatron/Fermilab) •  search for rare processes with small s (N = Ls ) LHC pp ATLAS and CMS : pp, general purpose 27 km ring used for e+e- LEP machine in 1989-2000 Start : Summer 2007 ALICE : heavy ions LHCb : pp, B-physics Heavy Quarkonia 2006

  4. Inelastic proton-proton • reactions: 109 / s • cc pairs 8 107 / s • bb pairs 5 106 / s • tt pairs 8 / s • Z  e e 15 / s • Higgs (150 GeV) 0.2 / s • Gluino, Squarks (1 TeV) 0.03 / s Cross Sections and Production Rates Rates for High luminosity L = 1034 cm-2 s-1: (LHC) LHC is a factory for: top-quarks, b-quarks, c-quarks, .Higgs, …… (The challenge: you have to detect them !) Heavy Quarkonia 2006

  5. Heavy Quarkonia Production at the LHC • The production rates for heavy quark flavors at the LHCwill be huge • total cross-sections • charm: 7.8 mb (7.81012 ev @ 1 fb-1) • bottom: 0.5 mb (0.51012 ev @ 1 fb-1) • top: 0.8 nb (0.8106ev @ 1 fb-1) • c,b cross-sections • equal for high pT in LO PQCD, differences expected from NLO (pT spectrum for c softer) • mass effects visible for low pT • Prediction of LHC rates by • tuningmodels withTevatron data • extrapolating to LHC energies Heavy Quarkonia 2006

  6. Various models in Quarkonium Production • The Color Evaporation Model (CEM) Assumes no correlation between the initial QQ state and the final quarkonium state. • The Color Singlet Model (CSM) Assumes each quarkonium state can only be produced by a QQ pair in the same color and angular momentum state as that quarkonium. • The Nonrelativistic QCD Model (NRQCD) Treats quarkonium as an approximately nonrelativistic system. When applied to production, this implies that QQ pairs produced with one set of quantum numbers can evolve into a quarkonium state with different quantum numbers, by emitting low energy gluons. Heavy Quarkonia 2006

  7. Heavy Quarkonia Production at the LHC II LHC • The LHCwill produce heavy quarkonia withhigh pT in large numbers • assess importance of individual production mechanisms • e.g. colour-singlet vs. colour-octet, factorisation Heavy Quarkonia 2006

  8. NRQCD Two gluon fusion a • NRQCD adds systematic nonrelativistic corrections to effective field theory using an expansion series in ν, (the velocity of the heavy quark in the quarkonium rest frame). • At high PT (PT >>mc) the dominant process in NRQCD is the fragmentation of a single gluon to a pair in a [8,3S1] state (c). In comparison to the color singlet fragmentation process in (b) this occurs at a higher order of vc (vc7 versus vc3 ) but at a lower order of αs (αs3 versus αs5). • Taking into account these facts, it is indeed plausible that the color octet process could explain the observed direct cross sections. b c d Heavy Quarkonia 2006

  9. Polarization Measurements at the Tevatron heavy quarkonia polarization allows for better discrimination between different models of e.g. NRQCD vs. colour-evaporation model CDF RUN I Recent measurementsApril 28, 2005http://www-cdf.fnal.gov/physics/new/bottom/050428.blessed-jpsi-polarization/ Heavy Quarkonia 2006

  10. ATLAS Detector • Calorimeters • Muons Spectrometer • Magnetic system • Inner Detector (ID) • Tracking (||<2.5, B=2T) : • -- Si pixels and strips • -- Transition Radiation Detector (e/ separation) • Calorimetry (||<5): • -- EM : Pb-LAr • -- HAD: Fe/scintillator (central), Cu/W-LAr (fwd) • Muon Spectrometer (||<2.7): • air-core toroids with muon chambers Length : ~ 46 m Radius : ~ 12 m Weight : ~ 7000 tons ~ 108 electronic channels ~ 3000 km of cables Heavy Quarkonia 2006

  11. Four sub-systems: Pixels (0.8 108 channels) σφ=12 μm, σz=66 μm Silicon Tracker (SCT) 5cm<radii<50cm(6 106 channels) σφ=16 μm, σz=580 μm Transition Radiation Tracker (TRT) 50<radii<100 cm (4 105 channels) σ=170 μm per straw Inner Detector (ID) The silicon detectors ~ 10 azimuthal position measurements, 10 - 20μm The TRT ~ 36 azimuthal position measurements, 150 microns. Heavy Quarkonia 2006

  12. Muon Spectrometer • The momentum of the muons is determined from the curvatures of their tracks in a toroidal magnetic field. • Muon tracks are identified and measured after their passage through ~2m of material. • Track measurement with =60m intrinsic resolution in three precision measurement stations (MDT). Heavy Quarkonia 2006

  13. Trigger & DAQ System • LVL1 decision made: • e, g, t, jet, m candidates • Identifies Regions of Interest • LVL2 uses Region of Interest data • Combines information from all detectors • Event Filter • Can be “seeded” by LVL2 result • potential full event access Heavy Quarkonia 2006

  14. Muon Trigger System • LVL-1 muon trigger: three trigger stations Resistive Plate Chambers (RPC) in the barrel and Thin Gap Chambers (TGC) in the end-caps. • Each station is made of 2 - 3 planes of strips / wires. • A coincidence between a strip(or wire) hit in the 1st station and hits in the 2nd or 3nd station. • Low pt trigger: p > 6GeV • High pt trigger: p > 20GeV. IP Heavy Quarkonia 2006

  15. g+g→J/Ψ +g Cross Sections The prompt J/Ψ direct production using 3 different parton distribution functions. CTEQ3L-Green CTEQ5L-Red CTEQ6M-Blue • Trigger efficiency (low luminosity) for pp→J/Ψ →μ(6GeV)μ(3GeV) is ~10% • Reconstruction algorithm efficiency ~60% PT(GeV/c) After one year we expect ~10 million events of pp→J/Ψ→μ-μ+ Heavy Quarkonia 2006

  16. Monte Carlo Study • Generation with Pythia 6.221 • Parton distribution function - CTEQ6M • The Octet model was implemented in Pythia 6.221 (adding two external differential cross-sections for pp→J/Ψ +X corresponding colored 3S1 and 1S0 +3P0) • Di-muon filter on PT greater than 3 and 6 GeV applied in the event production. • Geant-4 Simulation-> Digitization-> Reconstruction-> “My Analysis” algorithms. • Currently moving to Pythia 6.326 version Heavy Quarkonia 2006

  17. New Pythia versions • Implementation of NRQCD native in the new PYTHIA versions. • Previously used as external routines. • PYTHIA 6.326 enables a full charmonia and bottomonia production (simultaneous production ofψ’s andU’s,U(1S), U(2S)…. • The new PYTHIA code is under validation; • Realistic parameter values (e.g. NRQCD MEs) under studies. • The standard code doesn’t contain complete set of realistic default parameters. Heavy Quarkonia 2006

  18. Some Pythia settings • Initial (61) and final (71) state radiation -shower switched on. • Pmas(4,1)=1.5 ( charm mass=1.5GeV) • CTEQ6M parameters • Ckin(3)=3 - kinematic cut • BSignalFilter: muon PT1>6GeV, PT2>3GeV • BSignalFilter: |Eta| cut <2.5 Heavy Quarkonia 2006

  19. The Pythia parameters of NRQCD effective matrix elements ME Based on P. Nanson et al., “Bottom production” HEP-PH/0003142 Heavy Quarkonia 2006

  20. Comparison of charmonium production (LHC CM=14TeV) Pythia6.323(11.0.4)+External Color Octet All included subprocesses: 1.560E-02 mb 86 g + g -> J/Psi + g ---- 5.957E-03 mb 87 g + g -> chi_0c + g-- 2.175E-03 mb 88 g + g -> chi_1c + g--- 4.161E-03 mb 89 g + g -> chi_2c + g ---3.304E-03 mb • All included subprocesses 1.460E-01 • 421 g + g -> cc~[3S1(1)] + g 5.415E-04 • 422 g + g -> cc~[3S1(8)] + g 9.346E-03 • 423 g + g -> cc~[1S0(8)] + g 3.082E-03 • 424 g + g -> cc~[3PJ(8)] + g 5.336E-03 • 425 g + q -> q + cc~[3S1(8)] 2.316E-03 • 426 g + q -> q + cc~[1S0(8)] 6.610E-04 • 427 g + q -> q + cc~[3PJ(8)] 1.143E-03 • 428 q + q~ -> g + cc~[3S1(8)] 1.029E-05 • 429 q + q~ -> g + cc~[1S0(8)] 0.000E+00 • 430 q + q~ -> g + cc~[3PJ(8)] 1.013E-06 • 431 g + g -> cc~[3P0(1)] + g 2.729E-02 • 432 g + g -> cc~[3P1(1)] + g 3.551E-02 • 433 g + g -> cc~[3P2(1)] + g 3.837E-02 • 434 q + g -> q + cc~[3P0(1)] 5.726E-03 • 435 q + g -> q + cc~[3P1(1)] 7.982E-03 • 436 q + g -> q + cc~[3P2(1)] 8.634E-03 • 437 q + q~ -> g + cc~[3P0(1)] 0.000E+00 • 438 q + q~ -> g + cc~[3P1(1)] 4.524E-06 • 439 q + q~ -> g + cc~[3P2(1)] 3.118E-06 Filter 0.6% of the events pass di-muon filter with PT1>6GeV and PT2>3GeV |eta|<2.5,old PYEVNT model BR(pp-Jpsi)=9.3E-03mb*0.006(m3m6)=55nb Heavy Quarkonia 2006

  21. Events Kinematics Pythia versions: 6.326->Blue 6.221->Red (Rome Data) PT Distributions PT Pseudorapidity Events Multiplicity EM Heavy Quarkonia 2006

  22. First year of LHC at 900 GeV vs 14TeV Pythia6.326 CMS=900GeV Pythia6.326 CMS=14TeV All included subprocesses 1.460E-01 421 g + g -> cc~[3S1(1)] + g 5.415E-04 422 g + g -> cc~[3S1(8)] + g 9.346E-03 423 g + g -> cc~[1S0(8)] + g 3.082E-03 424 g + g -> cc~[3PJ(8)] + g 5.336E-03 • All included subprocesses 9.154E-03 • 421 g + g -> cc~[3S1(1)] + g 5.540E-05 • 422 g + g -> cc~[3S1(8)] + g 5.155E-04 • 423 g + g -> cc~[1S0(8)] + g 1.915E-04 • 424 g + g -> cc~[3PJ(8)] + g 3.279E-04 • 425 g + q -> q + cc~[3S1(8)] 1.809E-04 • 426 g + q -> q + cc~[1S0(8)] 5.753E-05 • 427 g + q -> q + cc~[3PJ(8)] 1.004E-04 • 428 q + q~ -> g + cc~[3S1(8)] 1.057E-06 • 429 q + q~ -> g + cc~[1S0(8)] 0.000E+00 • 430 q + q~ -> g + cc~[3PJ(8)] 2.391E-24 • 431 g + g -> cc~[3P0(1)] + g 1.663E-03 • 432 g + g -> cc~[3P1(1)] + g 2.010E-03 • 433 g + g -> cc~[3P2(1)] + g 2.186E-03 • 434 q + g -> q + cc~[3P0(1)] 4.906E-04 • 435 q + g -> q + cc~[3P1(1)] 6.539E-04 • 436 q + g -> q + cc~[3P2(1)] 7.201E-04 • 437 q + q~ -> g + cc~[3P0(1)] 4.278E-08 • 438 q + q~ -> g + cc~[3P1(1)] 1.035E-06 • 439 q + q~ -> g + cc~[3P2(1)] 1.538E-07 Filter 5% of the events pass di-muon filter with PT1>5GeV and PT2>0.5GeV ,old PYEVNT model BR(pp-Jpsi)=5.15E-04mb*0.05(m5m0.5)=26nb Heavy Quarkonia 2006

  23. Tunning Pythia: Multiple Interactions, new vs old models • Old model:ISR and FSR considered only for the hardest interaction. The new model allows radiation to be associated with all the interactions. An intermediate model implemented it in a disjoint matter where radiation was associated in stages. • MSTP(81) : (D=1) master switch for multiple interactions (MI), and also for the associated treatment of initial- and final-state showers and beam remnants. Its meaning depends on whether PYEVNT (old and intermediate models) or PYEVNW (new model) is called. • =0 : MI off; old model for PYEVNT, new model for PYEVNW. • =1 : MI on; old model for PYEVNT, new model for PYEVNW. • =10 : MI off; intermediate model for PYEVNT, new model for PYEVNW. • = 11 : MI on; intermediate model for PYEVNT, new model for PYEVNW. • = 20 : MI off; new model for PYEVNT or PYEVNW alike. • = 21 : MI on; new model for PYEVNT or PYEVNW alike. • Warning: many parameters have to be tuned differently for the old and new scenarios, such as PARP(81) - PARP(84), PARP(89) and PARP(90), and others are specific to each scenario. In addition, the optimal parameter values depend on the choice of parton densities and so on. Therefore you must pick a consistent set of values, rather than simply changing MSTP(81) by itself. Heavy Quarkonia 2006

  24. Parametes settings going from PYEVNT to PYEVNW Heavy Quarkonia 2006

  25. Kinematics with old and new model Blue -> Old PYEVNT model Red -> Intermediate PYEVNT model Green -> New (not tuned) PYEVNW model Currently under study Heavy Quarkonia 2006

  26. Selection of J/Ψ via Muon pair(ATLAS GEANT4 full simulation) • To properly select J/Ψ events, pairs of differently charged muons are chosen. Pt of the Lower Pt Muon MeV Heavy Quarkonia 2006

  27. J/Ψ mass reconstruction • The selection is based on the di-muon invariant mass reconstruction. Gaussian Fit Mean:3094.9 Sigma:42.9 Mass resolution σ(M2μ)=43MeV Heavy Quarkonia 2006

  28. Background • Where in the B-phys community the direct J/Ψ is considered as background our main contamination comes from .. g+g→ B →J/Ψ+X . • The cross-section for this process is : σ(g+g→B →J/ Ψ→ μμ)≈10-2μb . Signal / Background of O(1) Heavy Quarkonia 2006

  29. bb̃ events rejection (proper-time cut) The displacement of the two-track vertex from the beam line will be used to distinguish between prompt J/Ψ or from B-hadron decays. Log scale on axis Y N pp→J/ Ψ+X pp→ bb →J/ Ψ+X N ps Proper time Resolution 0.1 ps Heavy Quarkonia 2006 ps

  30. Efficiency and Purity of the proper-time cut • Selecting events with proper time less than 0.3 ps results in efficiency of 94% and contamination form bb->J/Ψ at a level of 8%. Heavy Quarkonia 2006

  31. Polarizations can be measured using the angular distribution of the daughter particles produced in the particle decay. The appropriate axis for defining a decay angle is the direction of the movement in the pp centre-of-mass frame (which is also the ATLAS lab frame). Polarization Measurement Technique The polarization parameter α, defined as , α=+1 transversely polarized production, helicity ±1. α =-1longitudinal (helicity 0) polarization. α= 0Unpolarized production consists of helicity states +1, 0 and -1, and corresponds to α= 0. The decay angle is called θ* and is defined to lie between the direction in the J/Ψ rest frame and the J/Ψ direction in the lab frame. Heavy Quarkonia 2006

  32. Polarization measurement J/Ψ polarizations can be measured applying appropriate fit to the angular distribution of the muons produced in its decay. J/Psi Pt 3-9GeV J/Psi Pt 9-16GeV Cos(θ) Cos(θ) J/Psi Pt 16-25GeV J/Psi Pt 25-40GeV Cos(θ) Cos(θ) Heavy Quarkonia 2006

  33. Summary • CERN / LHC committed to deliver first collisions in 2007 (PP at CM=900GeV) • First Physics at 14 TeV is expected in 2008. • Important ATLAS milestones have been passed in the construction, pre-assembly, integration and installation. • Major software and computing activities are underway as well, using (WLCG) for distributed computing. • Commissioning and planning for the early physics has started • In the low luminosity runs directJ/Ψ will be one of the first ATLAS “B phys” measurements. • This is one of the golden channels for the detector calibration and alignment. • ATLAS is still in the stage of validation and optimization of trigger and offline s/w • Currently study trigger and b-tagging effects • ATLAS B-physics trigger strategy rely on di-muon trigger for low luminosity when there is spare processing capacity. • Beginning to exercise full analysis chain using events generated with recent Pythia tuned MC Heavy Quarkonia 2006

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