1. 1 Perspectives for quarkonium production in CMS Carlos Lourenço, on behalf of CMSQWG 2008, Nara, Japan, December 2008

2. 2 A transverse slice through the CMS “barrel” Muon Barrel Drift Tube Chambers Resistive Plate Chambers Si Tracker Silicon pixels and micro-strips Calorimeters ECAL PbWO 4 HCAL Plastic Sci / Steel sandwich

3. 3 The CMS phase space coverage CMS + TOTEM: full φ and almost full η acceptance at the LHC  charged tracks and muons: |η| < 2.5  electrons and photons: |η| < 3  jets, energy flow: |η| 8.3 for neutrals, with the ZDC) HF  = -8 -6 -4 -2 0 2 4 6 8  excellent granularity and resolution  very powerful High-Level-Trigger

4. 4 The CMS assembly: a “LEGO” design

5. 5 Quarkonium production at LHC energies The LHC will provide pp and Pb-Pb collisions at high energies and luminosities Early times will be with pp collisions at 10 TeV (or maybe less) with instantaneous luminosities between 10 30 and 10 31 cm -2 s -1 (or maybe less) Depending on the machine performance, at some moment the energy will be increased to 14 TeV and the luminosity to 10 34 cm -2 s -1 The Pb-Pb runs will occur at 5.5 TeV per NN collision, with 10 27 cm -2 s -1 Pb-Pb instantaneous luminosity Quarkonium states will be produced with very high rates

6. 6 J/  detection and dimuon mass resolution in CMS CMS is ideally suited to measure quarkonium in the dimuon decay channel: large rapidity coverage (|  |<2.5) excellent dimuon mass resolution The good dimuon mass resolution is due to the good muon momentum resolution, which results from the matching between the tracks in the muon chambers and in the silicon tracker Because of the increasing material thickness traversed by the muons, the dimuon mass resolution changes with pseudo-rapidity, from ~15 MeV at  ~0 to ~40 MeV at  ~2.2

7. 7 The observed J/  yield results from: direct production decays from  ’ and  c states decays from B hadrons CMS will measure the inclusive, prompt and non-prompt (B decays) production cross sections In 1 or 2 days at 10 31 cm -2 s -1 (1 pb -1 of integrated luminosity), CMS will collect ~ 25 000 J/  events The J/  yield is extracted by fitting the dimuon mass distribution, separating the signal peak from the underlying background continuum Inclusive differential J/  cross sections CMS simulation

8. 8 Inclusive differential J/  cross section A : convolution between the detector acceptance and the trigger and reconstruction efficiencies, which depend on the assumed polarization corr : needed if MC does not match “reality” pp at 14 TeV 3 pb -1  ~ 75 000 J/  CMS simulation A Competitive with Tevatron results after only 3 pb -1 CMS simulation

9. 9 An unbinned maximum likelihood fit is made, in p T bins, to determine the non-prompt fraction, f B, using the dimuon mass and the pseudo proper decay length Feed-down from B meson decays B fraction fit J/  p T : 9–10 GeV/c CMS simulation Systematic error dominated by luminosity and polarization uncertainties

10. 10 Quarkonium production in Pb-Pb collisions      dN ch /d  = 3500

11. 11  →     : acceptances and mass resolutions CMS has a very good acceptance for dimuons in the Upsilon mass region The dimuon mass resolution allows us to separate the three Upsilon states: ~ 54 MeV within the barrel and ~ 86 MeV when including the endcaps Barrel: both muons in |  | < 0.8 Barrel + endcaps: muons in |  | < 2.4 p T (GeV/c)  Acceptance CMS simulation

12. 12 J/  →     : acceptances and mass resolutions barrel + endcaps barrel The material between the silicon tracker and the muon chambers (ECAL, HCAL, magnet’s iron) prevents hadrons from giving a muon tag but impose a minimum muon momentum of 3.5–4.0 GeV/c. This is no problem for the Upsilons, given their high mass, but sets a relatively high threshold on the p T of the detected J/  ’s. The low p T J/  acceptance is better at forward rapidities. The dimuon mass resolution is 35 MeV, in the full  region. barrel + endcaps p T (GeV/c) J/  Acceptance p T (GeV/c)  CMS simulation

13. 13 The High Level Trigger E T reach x2 x35 jets Pb-Pb at 5.5 TeV design luminosity CMS High Level Trigger: 12 000 CPUs of 1.8 GHz ~ 50 Tflops ! Executes “offline-like” algorithms pp design luminosity L1 trigger rate: 100 kHz Pb-Pb collision rate: 3 kHz (peak = 8 kHz)  pp L1 trigger rate  Pb-Pb collision rate  run HLT codes on all Pb-Pb events Pb-Pb event size: ~2.5 MB (up to ~9 MB) Data storage bandwidth: 225 MB/s  10–100 Pb-Pb events / second HLT reduction factor: 3000 Hz → 100 Hz Average HLT time budget per event: ~4 s Using the HLT, the event samples of hard processes are statistically enhanced by considerable factors

14. 14 p T reach of quarkonia measurements J/   ● produced in 0.5 nb -1 ■ rec. if dN/d  ~ 2500 ○ rec. if dN/d  ~ 5000 0.5 nb -1 : 1 month at 4x10 26 cm 2 s -1 Expected rec. quarkonia yields: J/  : ~ 180 000  : ~ 26 000 Statistical accuracy (with HLT) of  ’ /  ratio vs. p T should be good enough to rule out some models CMS simulation

15. 15  production in Ultra-Peripheral Pb-Pb Collisions   CMS will also measure Upsilon photo-production, occurring when the Pb nuclei fly through each other This will allow us to study the gluon distribution function in the Pb nucleus Around 500 events are expected after 0.5 nb -1, adding the e  e  and     decay channels using neutron tagging in the ZDCs CMS simulation

16. 16 Summary CMS has a high granularity silicon tracker, a state-of-the-art ECAL, large muon stations, powerful DAQ and HLT systems, etc.  excellent capabilities to study quarkonium production, in pp and Pb-Pb Dimuon mass resolutions: ~30 MeV for the J/  ; ~90 MeV for the , over |  |<2.4  Good S/B and separation of  (1S),  (2S) and  (3S) Expected pp rates: 25’000 J/  and 7’000  per pb -1 (1 or 2 days at 10 31 cm -2 s -1 )  J/  and  dimuons up to p T ~ 40 GeV/c in a few days Expected Pb-Pb rates: 180’000 J/  and 25’000  (1S) per 0.5 nb -1 (one month)  Studies of Upsilon suppression as signal of QGP formation J/  and  polarization, and  c → J/  studies require larger samples Further information can be found in: http://cms.cern.ch/iCMS/ (“B-physics” and “Heavy-Ions” Physics Analysis Groups) http://www.slac.stanford.edu/spires/find/hep/www?j=JPHGB,G34,N143 http://cms.cern.ch/iCMS/ http://www.slac.stanford.edu/spires/find/hep/www?j=JPHGB,G34,N143 http://www.slac.stanford.edu/spires/find/hep/www?j=JPHGB,G34,2307

17. 17 LHC proton beam in CMS, on September 10 CMS recorded several splash events when the proton beam was steered onto the collimators; halo muons were observed once beam started passing through CMS Detectors flooded by few hundred thousand muons resulting from 10 9 protons (one bunch) simultaneous hitting a collimator Correlation between the energies collected in the HCAL and ECAL calorimeters from several “beam-collimator collisions”

18. 18 “splash event”

19. 19 “halo muons event”

20. 20 Cosmic muons in CMS CMS recorded almost 300 million cosmic muons in one month of 24 / 7 running at full magnetic field and with all detectors operational A cosmic muon that traversed the barrel muon systems, the barrel calorimeters, and the silicon strip and pixel trackers Improved track quality in the strip tracker as the nominal design geometry is replaced by versions aligned with cosmic muons See http://www.cern.ch/cms-project-cmsinfo/ for more informationhttp://www.cern.ch/cms-project-cmsinfo/

21. 21 The 2010 QWG meeting will see the first CMS quarkonium results…