Perspectives for quarkonium production in CMS

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

2. A transverse slice through the CMS “barrel” Si TrackerSilicon pixelsand micro-strips CalorimetersECAL PbWO4HCAL Plastic Sci / Steel sandwich Muon BarrelDrift Tube ChambersResistive Plate Chambers

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| < 6.7 (plus η > 8.3 for neutrals, with the ZDC) • excellent granularity and resolution • very powerful High-Level-Trigger HF HF h = -8 -6 -4 -2 0 2 4 6 8

4. The CMS assembly: a “LEGO” design

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 1030 and 1031 cm-2s-1 (or maybe less) • Depending on the machine performance, at some moment the energy will be increased to 14 TeV and the luminosity to 1034 cm-2s-1 • The Pb-Pb runs will occur at 5.5 TeV per NN collision, with 1027 cm-2s-1 Pb-Pb instantaneous luminosity • Quarkonium states will be produced with very high rates

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. Inclusive differential J/y cross sections • 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 1031 cm-2s-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 CMS simulation

8. Inclusive differential J/y cross section A CMS simulation pp at 14 TeV3 pb-1  ~ 75 000 J/ CMS simulation A : convolution between the detector acceptanceand the trigger and reconstruction efficiencies, which depend on the assumed polarization corr : needed if MC does not match “reality” Competitive with Tevatron results after only 3 pb-1

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

10. Quarkonium production in Pb-Pb collisions dNch/dh = 3500 -

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

12. pT (GeV/c) h J/y → m+m-: acceptances and mass resolutions • 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 pT of the detected J/y’s. • The low pT J/y acceptance is better at forward rapidities. • The dimuon mass resolution is 35 MeV, in the full h region. J/y barrel +endcaps Acceptance barrel +endcaps barrel CMS simulation pT (GeV/c)

13. The High Level Trigger • 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 Pb-Pb at 5.5 TeV design luminosity ET reach x2 jets x35 x35

14. pT reach of quarkonia measurements ● produced in 0.5 nb-1 ■ rec. if dN/dh ~ 2500 ○ rec. if dN/dh ~ 5000 0.5 nb-1 : 1 month at 4x1026 cm2s-1 Expected rec. quarkonia yields: J/y : ~ 180 000  : ~ 26 000 J/y Statistical accuracy (with HLT) of’ /  ratio vs. pTshould be good enough to rule out some models CMS simulation  CMS simulation

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 m+m- decay channels using neutron tagging in the ZDCs   CMS simulation CMS simulation

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 1031 cm-2s-1) J/ and  dimuons up to pT ~ 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 cc → J/y + g 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://www.slac.stanford.edu/spires/find/hep/www?j=JPHGB,G34,2307

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 109 protons (one bunch) simultaneous hitting a collimator Correlation between the energies collected in the HCAL and ECAL calorimeters from several “beam-collimator collisions”

18. “splash event”

19. “halo muons event”

20. Cosmic muons in CMS CMS recorded almost 300 million cosmic muons in one month of 24 / 7 runningat 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 trackeras the nominal design geometry is replaced by versions aligned with cosmic muons See http://www.cern.ch/cms-project-cmsinfo/ for more information

21. The 2010 QWG meeting will see the first CMS quarkonium results… See you at Fermilab