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

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

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

4 730 members 54 institutes 15 countries

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 “dedicated to heavy flavour physics at the LHC”

bb production at LHC 6 bb pair production correlated  σ bb ~ µb TeV)  15<  <300 mrad, unique acceptance Luminosity limits to ~2  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 

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) 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

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

Detectors’ Efficiency 9 Extremely high efficiency for all subdetectors

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

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)

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

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

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

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

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

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.

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.

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

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 -

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

Open charm cross section 22

Open charm cross section 23

Open charm cross section 24

Open charm cross section 25

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

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

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 7 TeV 28

Thank you 29

back up 30

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 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

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

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)

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)

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 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+

Data Set of J/  (1) 38

Data Set of J/  (2) 39

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 -  + )  +

Selections of D+ and Ds 41 K,  : Prob(  2 (track)) > pT > 200 MeV/c p > 3.2 GeV/c  2 (IP) > 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 → (  →      +

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