1. Open Charm and Charmonium Production: First Results from LHCb Zhenwei YANG @Tsinghua Univ. on behalf of the LHCb collaboration 21-24, October, 2010 IHEP, Beijing, China 1

2. Outline  Physics ambition of LHCb  LHCb detector  Physics interests on charm  First results on charmonium and open charm  Summary and perspectives 2

3. ➢ Success running in 2009 @ 2.36 TeV ➢ first collision @ 7 TeV on March 30 ➢ Integrated Lumi ~ ?? pb -1 (?? Oct, 2010) LHC Tunnel Geneva CERN 3

4. 4 730 members 54 institutes 15 countries

5. Physics Aims of LHCb New Physics CP violation: precision measurements of CKM angles rare decay of beauty and charm hadrons Heavy Flavour Physics B production B c, b-baryon physics charm decays (e.g. D-mixing) tau lepton flavour violation...... 5 “dedicated to heavy flavour physics at the LHC”

6. bb production at LHC 6 bb pair production correlated  σ bb ~ 300-500 µb (@7-14 TeV)  15<  <300 mrad, unique acceptance Luminosity limits to ~2  10 32 cm -2 s -1  Maximize probability of a single interaction per crossing  2fb -1 per nominal year(10 7 s), ~10 12 bb pairs pear year 

7. LHCb Detector μ+μ+ μ-μ- Tracking System (TT,T1-T3) Efficiency ~ 95(94.3)% Ghost ~ 5(7.7)% Δp/p~ 0.5(0.55)%(long tracks) Silicon strip detector σ x/y ~ 10(15.5) μm σ z ~ 60(91) μm σ IP ~ 21(25) μm @2GeV/c beam 2 *long tracks: tracks passing trough VELO,TT,T1-T3 beam 1 7 Muon System (M1-M5) μ-id ：  (  ) ~94(97) %, mis-id:  (  ) ~ 3(2) % b hadron

8. LHCb Data Taking 8 Stable data taking with high efficiency in all systems, globally increasing with time. to be updated

9. Detectors’ Efficiency 9 Extremely high efficiency for all subdetectors

10. Physics Interests on Charm 1) J/  cross-section (and polarization)  Production mechanism still not well understood, theoretical interests on direct J/   Three main sources of J/  1) Direct J/  2) Decay from heavier charmonium 3) Decay from b-hadrons  fractions of heavier charmonia are helpful 2) Essentially related to many investigations of CP violation and rare decay 3) Understanding of charm is fundamental for later analysis 10 Prompt J/  J/  from b

11. Cross section(both prompt J/  and J/  from b) Separate “prompt J/  ” from “J/  from b” by fitting pseudo-proper time t z Measurement of J/  cross section 11 σ( incl. J/  ) σ( J/  from b)

12. Measurement of J/  cross section good approximation of average b lifetime well described by exponential distribution 12

13. Event Selection of J/  Data Sample (14.15 ± 1.42) nb -1 (low pile-up conditions) Event selection 2 muons – with fully reconstructed tracks (VELO + Tracker) – identified bymuon system – good vertex reconstructed – p T > 700 MeV/c – Mass window for signal definition: (M J/ψ ± 390) MeV/c 2 Trigger L0 – single muon, p T > 480 MeV/c HLT: – single muon, p T > 1.3 GeV/c.OR. muon pair with M μμ > 2700 MeV/c 2 13

14. Mass fit 14 Fit results (2.5<y<4, p T <10 GeV/c): Signal = 2872 ± 73 S/B = 1.3 μ = (3088 ± 0.4) MeV/c 2 σ = (15.0 ± 0.4) MeV/c 2 Signal: Crystal Ball function Background: 1 st order polynomial

15. t z Fit Result 15 χ 2 /ndof=1.6 1)Background from invariant mass sidebands 2)Crosscheck with a binned fit gives consistent results

16. Efficiencies: ε = ε acc x ε rec x ε trig 16  0<PT<10 GeV/c divided into 10 bins  integrate over 2.5<y<4 due to low statistics  plenty of cross check with data

17. Total Efficiency and Polarization Effect ε depends strongly on polarization treated as systematic errors for first data 17 With more statistics, a direct measurement of polarization with full angular analysis, in different reference frames and bins of y and p T, is foreseen.

18. Preliminary Results 18 Extrapolations with PYTHIA 6.4 (LEP hadronization fractions assumed) Systematic errors mainly come from data/MC discrepancy. Dominant contributions from trigger and tracking efficiencies.

19. More Data 19 Will measure also polarization Region of measurement (y, p T ) will be extended with more data, some overlap to CMS/ATLAS Much more data since ICHEP several 100k events/pb -1

20. Heavier Charmonia 20  M = M  J/  M  J/   c  J/   (2s)  J/  1)Also seen hints of X(3872). 2)With more statistics, we will measure  (  c1 +  c2 )/  (J/  ) separately for prompt  c and  c from b, and measure cross section of  (2S).  (2s)  μ + μ -

21. Open Charm 21 D 0 → K -  + D *+ → (D 0 →K -  + )  + D+ →K- + +D+ →K- + + D s → (  →      +

22. Open charm cross section 22

23. Open charm cross section 23

24. Open charm cross section 24

25. Open charm cross section 25

26. Open charm cross section First measurement at √s=7 TeV. Measure cross section vs y, p T in ~2 nb -1, with open trigger. Good agreement with expectations! 26 Extrapolating to all pT and 4p can also confirm the expectation on ratio at √s=7TeV s(pp→ccX) ≈ 20 x s(pp→bbX)  Good news for LHCb charm program

27. Measurement of  (D + )/  (D s + ) 27 Consistent with PDG: 3.08  0.70

28. Summary and Perspectives LHCb producing physics quality measurements Cross sections of prompt J/  and J/  from b measured separately Cross sections of D 0,D*,D +,D s are measured, good agreement with theor. expectations Heavier charmonia well reconstructed and waiting for more statistics  (bb) determined in forward region @ 7 TeV 28

29. Thank you 29

30. back up 30

31. Measurement of σ(pp → bbX) measure right-sign D 0 μ - pairs using tracks not pointing at primary vertex, but which form a common vertex D 0 mesons produced are not only produced in B-decays - but also “prompt” From PDG b in B±/B 0 /B s /b-baryon admixture →D 0 l νX :BR = 6.82% ±0.35% Br(D 0 → K π) = (3.91 ± 0.01)% production fractions taken from Heavy Flavor Averaging Group (LEP) Idea: using B→D 0 Xμν Example: only mode used

32. 32 Prompt from B Using log(IP) to separate direct D-meson and D meson from b Open (microbias trigger): 2.9 nb -1 Measurement of σ(pp → bbX) Muon (1 Muon) trigger: 12.2 nb -1 RS WS

33. Measurement of σ(pp → bbX) 33 σ( pp → bbX) = 284 ± 20 ± 49 μb (assuming LEP frag. fractions) σ( pp → H b X, 2 < η(H b ) < 6) = 75.3 ± 5.4 ± 13 μb Extrapolation: total bb production cross section at √s = 7 TeV

34. μ+μ+ μ-μ- b hadron HCAL:  (E)/E= (69  5)% E -1/2  (9  2) % (E in GeV) RICH1&RICH2 π/K id ：  (  ) ~95(96) % ， mis-id ~ 5(7) % ， beam 2 beam 1 LHCb Detector (2) 34 ECAL:  (E)/E= 10% E -1/2  1 % (E in GeV)

35. Cross section(both prompt J/  and J/  from b) Separate “prompt J/  ” from “J/  from b” by fitting pseudo-proper time t z Measurement of J/  cross section 35 σ( incl. J/  ) σ( J/  from b)

36. Open charm cross-sections 36 Extrapolating to all p T and 4  can also confirm the expectation on ratio at √s=7TeV  (pp→ccX) ≈ 20 x  (pp→bbX)  Good news for LHCb charm program

37. 37 Open charm (D 0,D*,D +,D s ) cross-sections First measurement at √s=7 TeV. Measure cross section vs y, p T in ~2 nb -1, with open trigger. Impact parameter distribution used to separate prompt D 0,+,D +, D s from secondary. Good agreement with expectations! DsDs D+D+

38. Data Set of J/  (1) 38

39. Data Set of J/  (2) 39

40. Selections of D0 & D* 40 K,  :  2 (track)/DoF < 9  2 (IP) > 9 pT > 700 MeV/c K :  LL(K-  ) >  :  LL(K-  ) D 0 :  2 (vertex) <9  2 (flight) > 16  2 (IP) < 9  < 12 mrad K,  :  2 (track)/DoF < 10 K,  D :  2 (IP) > 9 K :  LL(K-  ) > 0  :  LL(  -K) > 0 D 0 :  2 (vertex) <9 c  > 90  m  2 (IP) < 9 D *+ :  2 (vertex)< 9 D 0 → K -  + and D *+ → (D 0 →K -  + )  +

41. Selections of D+ and Ds 41 K,  : Prob(  2 (track)) > 10 -4 pT > 200 MeV/c p > 3.2 GeV/c  2 (IP) > 3.0 2 daugthters: pT > 400 MeV/c  2 (IP) > 10 1 daughter:  2 (IP) > 50 K :  LL(K-  ) > 3.3  :  LL(  -K) > -10 D+ :  2 (vertex) <8  < 14 mrad  2 (flight) > 90   < 0.01 ns K,  :  2 (track)/DoF<4 K :  2 (IP) > 2  :  2 (IP) > 10 K :  LL(K-  ) > 9  :  LL(  -K) > -2  : |  M|<20MeV/c 2 Ds :  2 (vertex)/DoF<5 Ds :  2 (flight)> 67 D + →K -  +  + and D s → (  →      +

42. Measurement of J/  cross section Cross section(both prompt J/ψ and J/ψ from b) Measurements restricted to: 2.5<y J/ψ <4 0<pT J/ψ <10 GeV/c because of the small statistics available Results on: dσ/dpT ( incl. J/ψ) in 10 bins of pT J/ψ, 0<pT J/ψ <10 σ( incl. J/ψ) σ( J/ψ from b) 42