Post on 18-Dec-2015
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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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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 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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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
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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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