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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

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Outline

Physics ambition of LHCbLHCb detectorPhysics interests on charmFirst results on charmonium and open

charmSummary and perspectives

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

LHC Tunnel

Geneva

CERN

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730 members54 institutes15 countries

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Physics Aims of LHCb

• New PhysicsCP violation: precision measurements of CKM anglesrare decay of beauty and charm hadrons

• Heavy Flavour PhysicsB productionBc , b-baryon physicscharm decays (e.g. D-mixing)tau lepton flavour violation......

“dedicated to heavy flavour physics at the LHC”

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bb production at LHCbb pair production correlatedσbb ~ 300-500 µb (@7-14 TeV)15<<300 mrad, unique acceptance

Luminosity limits to ~21032 cm-2s-1

Maximize probability of a single interaction per crossing2fb-1 per nominal year(107s), ~1012bb pairs pear year

LHCb Detector

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 σx/y ~ 10(15.5) μm σz ~ 60(91) μm σIP ~ 21(25) μm @2GeV/c

beam 2

*long tracks: tracks passing trough VELO,TT,T1-T3

beam 1

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Muon System (M1-M5) μ-id ： e(mm) ~94(97) %, mis-id: e (pm) ~ 3(2) %

b hadron

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LHCb Data Taking

Stable data taking with high efficiency in all systems,globally increasing with time.

to be updated to be updated

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Detectors’ Efficiency

Vertex Locator

Tracker Turic

ensisRICH 1

Inner Tracker

Outer TrackerRICH 2

Scintillator P

ad DetectorPreShower

Electromagnetic Calorim

eter

Hadron Calorimeter

Muon station 1

Muon syste

m 2-5

80 82 84 86 88 90 92 94 96 98 100

99.29

99.44

98.47

98.32

99.63

99.27

100.00

99.97

99.85

99.79

99.52

99.95

Efficiency (channels)

%

Extremely high efficiency for all subdetectors

Physics Interests on Charm1) 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

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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 tz

Measurement of J/ cross section

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trigrecacc

/ oftion reconstruc from Signals:

)/(

)/(

JN

JBrL

JN

σ( incl. J/)σ( J/ from b)

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Measurement of J/ cross section

• good approximation of average b lifetime• well described by exponential distribution

/

/

Jz

Jzz p

Mdt

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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– pT > 700 MeV/c– Mass window for signal definition: (MJ/ψ ± 390) MeV/c2

• Trigger L0– single muon, pT > 480 MeV/c

• HLT:– single muon, pT > 1.3 GeV/c .OR. muon pair with Mμμ > 2700 MeV/c2

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Mass fit

Fit results (2.5<y<4, pT<10

GeV/c):

Signal = 2872 ± 73

S/B = 1.3

μ = (3088 ± 0.4) MeV/c2

σ = (15.0 ± 0.4) MeV/c2

Signal: Crystal Ball functionBackground: 1st order polynomial

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tz Fit Result

χ2/ndof=1.61)Background from

invariant mass sidebands

2)Crosscheck with a binned fit gives consistent results

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Efficiencies: ε = εacc x εrec x εtrig

0<PT<10 GeV/c divided into 10 binsintegrate over 2.5<y<4 due to low statisticsplenty of cross check with data

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Total Efficiency and Polarization Effect • ε depends strongly on polarization• treated as systematic errors for first data

With more statistics, a direct measurement of polarization with full angular analysis, in different reference frames and bins of y and pT , is foreseen.

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Preliminary Results

μb10.119.065.7)45.2,GeV/10,/ incl.( 87.027.1

ycpJ Tμb13.006.081.0)45.2,GeV/10,from/( ycpbJ T

Extrapolations with PYTHIA 6.4 (LEP hadronization fractions assumed)

μb5924319)( Xbbpp

Systematic errors mainly come from data/MC discrepancy. Dominant contributions from trigger and tracking efficiencies.

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More Data

Will measure also polarization Region of measurement (y, pT) will

be extended with more data, some overlap to CMS/ATLAS

Much more data since ICHEP several 100k events/pb-1

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Heavier Charmonia

DM = M (J/ ) -yg M(J/ )y

ccJ/ ( ) y mm g

(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-

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Open CharmD0 → K- p+ D*+→ (D0→K-p+ )p+

D+ →K- p+ p+ Ds→ (f→K-K+)p+

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Open charm cross section

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Open charm cross section

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Open charm cross section

Open charm cross section

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Open charm cross section First measurement at √s=7 TeV. Measure cross section vs y, pT in ~2 nb-1, with

open trigger. Good agreement with expectations!

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

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Measurement of (D+)/(Ds+)

Consistent with PDG: 3.080.70

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Summary and Perspectives• LHCb producing physics quality measurements• Cross sections of prompt J/ and J/ from b

measured separately• Cross sections of D0,D*,D+,Ds are measured,

good agreement with theor. expectations• Heavier charmonia well reconstructed and

waiting for more statistics• (bb) determined in forward region @ 7 TeV

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Thank you

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back up

Measurement of σ(pp → bbX)

00 DB

measure right-sign D0 μ- pairs using tracks not pointing at primary vertex, but which form a common vertex

D0 mesons produced are not only produced in B-decays - but also “prompt”

From PDG• b in B±/B0/Bs/b-baryon admixture →D0 l νX :BR = 6.82% ±0.35%• Br(D0 → K π) = (3.91 ± 0.01)%

production fractions taken from Heavy Flavor Averaging Group (LEP)

Idea: using B→D0Xμν

Example:

KD0

only mode used

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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

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Measurement of σ(pp → bbX)

σ( pp → bbX) = 284 ± 20 ± 49 μb (assuming LEP frag. fractions)

σ( pp → Hb X, 2 < η(Hb) < 6) = 75.3 ± 5.4 ± 13 μb

Extrapolation: total bb production cross section at √s = 7 TeV

μ+

μ-b hadron

HCAL: s(E)/E= (695)% E-1/2 (9 2) % (E in GeV)

RICH1&RICH2π/K id： e(KK) ~95(96) % mis-id ~ 5(7) %

beam 2beam 1

LHCb Detector (2)

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ECAL: s(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 tz

Measurement of J/ cross section

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trigrecacc

/ oftion reconstruc from Signals:

)/(

)/(

JN

JBrL

JN

/

/

Jz

Jzz p

Mdt

σ( incl. J/)σ( J/ from b)

Open charm cross-sections

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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

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Open charm (D0,D*,D+,Ds) cross-sections First measurement at √s=7 TeV. Measure cross section vs y, pT in ~2 nb-1,

with open trigger. Impact parameter distribution used to

separate prompt D0,+,D+, Ds from secondary.

Good agreement with expectations!

Ds

D+

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Data Set of J/ (1)

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Data Set of J/ (2)

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Selections of D0 & D*

K,p : c2(track)/DoF < 9 c2(IP) > 9 pT > 700 MeV/c K : DLL(K-p) > p : DLL(K-p) D0 : c2(vertex) <9 c2(flight) > 16 c2(IP) < 9 q < 12 mrad

K,p : c2(track)/DoF < 10K,pD : c2(IP) > 9 K : DLL(K-p) > 0 p : DLL(p-K) > 0 D0 : c2(vertex) <9 ct > 90 mm c2(IP) < 9D*+ : c2(vertex)< 9

D0 → K- p+ and D*+→ (D0 →K-p+ )p+

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Selections of D+ and Ds

K,p : Prob(c2(track)) > 10-4

pT > 200 MeV/c p > 3.2 GeV/c c2(IP) > 3.0 2 daugthters: pT > 400 MeV/c c2(IP) > 10 1 daughter: c2(IP) > 50 K : DLL(K-p) > 3.3 p : DLL(p-K) > -10 D+ : c2(vertex) <8 q < 14 mrad c2(flight) > 90 t < 0.01 ns

K,p:c2(track)/DoF<4K : c2(IP) > 2p : c2(IP) > 10 K : DLL(K-p) > 9p : DLL(p-K) > -2 f : |DM|<20MeV/c2

Ds : c2(vertex)/DoF<5 Ds : c2(flight)> 67

D+ →K- p+ p+ and Ds→ (f→K-K+)p+

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Measurement of J/ cross section• Cross section(both prompt J/ψ and J/ψ from b)

• Measurements restricted to: 2.5<y J/ψ <40<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)

)/(

)/(

JBrL

JN