first results & prospects for charm physics @ lhcb
DESCRIPTION
First results & Prospects for Charm Physics @ LHCb. Vanya BELYAEV ( Nikhef , Amsterdam) on behalf of LHCb Collaboration. Outline. For LHCb results on J/ y see talk by Giovanni Passaleva, - PowerPoint PPT PresentationTRANSCRIPT
First results & Prospects
for Charm Physics @ LHCb
Vanya BELYAEV (Nikhef, Amsterdam)
on behalf of LHCb Collaboration
Vanya Belyaev (Nikhef) 2
Outline
•Why (open) Charm?
•The first resultsOpen Charm peaks
Open Charm cross-section• Perspectives• Mixing & CP violation• yCP, ACP
• Rare decays
23 July 2k+10
For LHCb results on J/y see talk by Giovanni Passaleva,
Prompt J/y and b →J/yX production in pp-collision at √s=7TeV, track#5, 22 July 9:30
Vanya Belyaev (Nikhef) 3
Why charm?
• Charm production in forward region 2<y<5 at LHC energy is an unique & unexplored domain
• Rare decays (D0→m+m-), mixing and CP-violation are well suitable for NP search
• Deep understanding of charm is nessessery for many crucial measurement with beauty
D0→Kspp decay model for GGSZ-measurement of angle-g of Unitarity Triangle through B→DK
• Collecting experience, testing tools & skills, warming up for analyses of beauty
23 July 2k+10
Vanya Belyaev (Nikhef) 4
LHCb: forward spectrometer
• Selection of good tracks: c2(track)/DoF
• Use RICH to separate kaons from pions: DLL(K-p) for kaons, DLL(p-K) for pions
• Pointing criteria for final state particles: • large c2 for impact parameter c2(IP)
• Pointing criteria for mother particle• small c2 for impart parameter c2(IP) • small angle q between momentum
and vector from origin to decay vertex
• Large lifetime of charm particle• “large” c2 of vertex separation:
c2(flight) • “large” lifetime ct
23 July 2k+10
O(2nb-1
) : minimum bias trigger
O(14nb-1): “low-luminosity”
Vanya Belyaev (Nikhef) 5
D0 → K- p+ and D*+→ (D0 →K-p+ )p+
23 July 2k+10
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 < 10
K,pD : c2
(IP) > 9
K : DLL(K-p) > 0
p : DLL(p-K) > 0
D0
: c2
(vertex) <9
ct > 90 mm
c2
(IP) < 9
D*+
: c2
(vertex)< 9
Vanya Belyaev (Nikhef) 6
D+ →K- p+ p+ and Ds→ (f→K-K+)p+
23 July 2k+10
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<4
K : c2
(IP) > 2
p : c2
(IP) > 10
K : DLL(K-p) > 9
p : DLL(p-K) > -2
f : |DM|<20MeV/c2
Ds : c2
(vertex)/DoF<5
Ds : c2
(flight)> 67
Vanya Belyaev (Nikhef) 7
From plots to cross-sections
Measure the cross-section in bins of pT and rapidity
• Luminosity: 1.81±0.18nb-1
• Efficiency:• Trigger: ‘no-trigger’
• Reconstruction Efficiency• Tracking efficiency from data
• Particle Identification Efficiency• Determined on data using the clean Ks, L0 and f peaks
• Selection efficiency: rely on Monte Carlo with the detailed cross-checks on data
23 July 2k+10
Eric van Herviinen
LHCb Trigger System, track #1, 22 July, 10:15
Silvia Borghi Performance of Tracking System of LHCb Experiment, track #1, 22 July,
11:36
Andrew Powell
ParticleID @ LHCb, track #1, 22 July, 14:00
Vanya Belyaev (Nikhef) 8
Cascade charm b→c
• There is cascade production of open charm in decays of b→(D,D*,Ds)
• The pointing criteria of D-mesons: log(IP)
23 July 2k+10
The similar technique has been used for measurement of
beauty cross-section , see talk by Sheldon Stone,
First physics results from LHCb, track #1, 23 July, 10:00
log(IP)
Vanya Belyaev (Nikhef) 9
Systematics
• Absolute luminosity: overall 10%
• Trigger efficiency/ “no-trigger” negligible
• Tracking efficiency: extract from data, conservatively: 3%/track
• Selection efficiency: variation of cuts, compare data and Monte Carlo: 0.5-4%
• Charm from beauty: ~5%
• Signal extraction, fits, binning effects: ~3%
• Particle ID efficiency: from data, cross-checked with no-PID selections: ~3%
23 July 2k+10
Vanya Belyaev (Nikhef) 10
D0 cross-section “shape”
23 July 2k+10
Theory:
Cacciary M., Frixione, S., Mangano, M.,
Nason, P. Ridolfi, G.
Vanya Belyaev (Nikhef) 11
D*+ cross-section
23 July 2k+10
Vanya Belyaev (Nikhef) 12
D+ cross-section
23 July 2k+10
Vanya Belyaev (Nikhef) 13
Ds cross-section
23 July 2k+10
Vanya Belyaev (Nikhef) 14
Other Charm peaks
23 July 2k+10
D0
→p+p
-
D0
→K-p+p0
D*+
→ ( D0
→K-p+p+p-)p+
D+
→Ksp+
D0
→pp
D*+
→ ( D0
→Ksp+p+)p+
Vanya Belyaev (Nikhef) 15
Prospects with Charm
• Huge yields are expected for O(100pb-1)
23 July 2k+10
O(50nb-1
)
D0
→K+K-
Vanya Belyaev (Nikhef) 16
Probe New Physics in charm
yCP from lifetime difference between D0→KK and D0→K p
23 July 2k+10
D0
→ Kp
D0
→ KK
Proper lifetime
Vanya Belyaev (Nikhef) 17
Probe New Physics in charm
•Mixing parameters x’2 and y [LHCb-2007-049]
N (D0→Kp, wrong sign) = 2.5×103 / 100 pb-1 with B/S~2.5
• Search for direct CP-violation in D+ →K-K+p+
• Search for rare D0 → m+m- expected UL 4×10-8 @ 90CL for 100 pb-1
23 July 2k+10
Vanya Belyaev (Nikhef) 18
Summary
• LHCb is a great detector for charm physics• High Rate• Good momentum and spatial resolution• Particle identification
• LHCb has started successfully its charm physics program with the observation of charm peaks and measurement of open charm cross section
• Year 2k+10 and 2k+11 • High statistics measurements in charm sector
Stay tuned23 July 2k+10
Vanya Belyaev (Nikhef) 19
The basic principles of event selection
• Selection of good tracks: c2(track)/DoF
• Use particle identification to separate kaons from pions• “large” DLL(K-p) for kaons,
• “large” DLL(p-K) for pions
• Pointing criteria for final state particles:• “large” c2 for impact parameter c2(IP)
• Pointing criteria for mother particle• “small” c2 for impart parameter c2(IP)• small angle q between momentum and vector from origin to
decay vertex
• Large lifetime of charm particles• “large” c2 of vertex separation: c2(flight) • “large” lifetime c t
23 July 2k+10