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Physics at LHC 2008 Split, Croatia, 29 Sep - 4 Oct 2008. (Towards) First Physics with LHCb. Collaboration. on behalf of the. Beam induced “splash” in LHCb. Introduction Detector overview and performance Extracting physics from (very) first data. p resented by Andreas Schopper (CERN). - PowerPoint PPT Presentation
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(Towards) First Physics with LHCb(Towards) First Physics with LHCb
presented byAndreas Schopper (CERN)
on behalf of the Collaboration
Introduction Detector overview and performance Extracting physics from (very) first data
Be
am
ind
uce
d “
spla
sh”
in L
HC
b Physics at LHC 2008
Split, Croatia, 29 Sep - 4 Oct 2008
Andreas SchopperSplit, 2 October 2008
Physics at LHC 2008 2
LHCb is a heavy flavour precision experiment searching for new physics in CP-Violation and Rare Decays
LHCb is a heavy flavour precision experiment searching for new physics in CP-Violation and Rare Decays
New Physics models introduce new particles, dynamics and/or symmetries at a higher energy scale (expected in the TeV region) with virtual particles that appear e.g. in loop mediated processes
B-physics measurements probe New Physics and are complementary to direct searches will allow to understand the nature and flavour structure of possible New Physics
t,c,u
t,c,u
W W
s,d
b s,d
b
0B0B
Box diagram
0B
,K0s
b
s,ds
s,d
ss
Penguin diagram
stsSMstd
SMd
tstdSM
VV
Vm
2arg,2arg 22
2,
??
New Physics
d
m
s
Andreas Schopper
Search for New PhysicsSearch for New Physics
Split, 2 October 2008
Physics at LHC 2008 3
SM consistency at 7% level
CDF Public Note 9458 (August 2008)
are New physics already around the corner?
see talks by Andrei Golutvin, Alessia Satta, Val Gibson, William Robert Reece and poster by Lesya Shchutska and Bogdan Popovici
LHCb key measurements
In CP–violation: Bs-Bs mixing angle s
weak phase in trees weak phase in loops
In Rare Decays: branching ratio of Bs
forward-backward asymmetry in B K*
polarization of photon in radiative penguin decays
(s=-2βs)
Andreas SchopperSplit, 2 October 2008
Physics at LHC 2008 4
B production in LHCbB production in LHCb
pp interactions/crossing
LH
Cb
n=0
n=1
boost
b
b
bb pair production correlated and sharply peaked forward-backward Single-arm forward spectrometer : θ~15-300 mrad (rapidity range: 4.9>η>1.9) Cross section of bb production in LHCb acceptance: σbb ~ 230 µb B+ (40%), B0 (40%), Bs (10%), b-baryons (10%), Bc (< 0.1%)
LHCb limits luminosity to few 1032 cm-2s-1 instead of 1034 cm-2s-1 by not focusing the beam as much as ATLAS and CMS maximizes probability of a single interaction per crossing design luminosity soon after start-up
collect 2fb-1 per nominal year ~ 1012 bb pairs produced per year
Andreas Schopper 5
Detector overview and performance Detector overview and performance
Split, 2 October 2008
Physics at LHC 2008
walk through the detectorwith the example of a Bs→DsK decay
Andreas SchopperSplit, 2 October 2008
Physics at LHC 2008 6
B-Vertex MeasurementB-Vertex Measurement
Vertex Locator (Velo)Silicon strip detector with ~ 5 mm hit resolution 30 mm IP resolution
Vertexing:• trigger on impact parameter• measurement of decay distance (time)
Ds
BsK
K
K
d~1cm
47 mm 144 mm
440 mmPrimary vertex
Decay time resolution = 40 fs
(s t) ~40 fs
Example: Bs → Ds K
Andreas Schopper
Momentum and Mass measurement Momentum and Mass measurement
Momentum meas. + direction (VELO): Mass resolution for background suppression
Split, 2 October 2008
Physics at LHC 2008 7
btag
Bs K
K
p+, K
Ds
Primary vertex
Bs→ Ds KBs →Ds p
Mass resolutions ~14 MeV
Andreas Schopper 8
Particle IdentificationParticle Identification
RICH2: 100 m3 CF4 n=1.0005
RICH: K/p identification using Cherenkov light emission angle
RICH1: 5 cm aerogel n=1.03 4 m3 C4F10 n=1.0014
Split, 2 October 2008
Physics at LHC 2008
btag
Bs K
K
,K
Ds
Primary vertex
KK : 96.77 ± 0.06%pK : 3.94 ± 0.02%
Bs → Ds K
Andreas Schopper 9
Particle identification and L0 triggerParticle identification and L0 trigger
e
h
Calorimeter system : • Identify electrons, hadrons, π0 ,γ• Level 0 trigger: high ET electron and hadron
btag
Bs K
K
K
Ds
Primary vertexSplit, 2 October 2008
Physics at LHC 2008
ECAL (inner modules): σ(E)/E ~ 8.2% /√E + 0.9%
Andreas Schopper
Particle identification and L0 triggerParticle identification and L0 trigger
m
Muon system: • Level 0 trigger: High Pt muons• contributing to flavour tagging:
eD2 = e (1-2w)2 6% btag
Bs K
K
K
Ds
Primary vertexSplit, 2 October 2008
Physics at LHC 200810
Andreas SchopperSplit, 2 October 2008
Physics at LHC 2008
11
LHCb triggerLHCb trigger
HLT rate
Event type Physics
200 Hz Exclusive B candidates
B (core program)
600 Hz High mass di-muons
J/, bJ/X (unbiased)
300 Hz D* candidates Charm (mixing & CPV)
900 Hz Inclusive b (e.g. bm)
B (data mining)
HLT: high IP, high pT tracks [CPU farm] then full reconstruction of event
40 MHz
1 MHz
2 kHz
L0: high pT (m, e, g, h) [hardware, 4 ms]
Storage (event size ~ 35 kB)
Detector
Note: decay time dependent efficiency: eg. Bs → Ds K
Proper time [ps]
Effici
ency
btag
BsKK
K
Ds
Primary vertex
L0 e
ffici
ency
(%)
11
Andreas Schopper
Split, 2 October 2008
OT CaloMuon
Top view
Status of LHCbStatus of LHCb
Physics at LHC 2008
12
Clean event from halo muons
LHCb detector fully installed and commissioned (except M1), including L0 trigger All sub-detectors have undergone the first time and space alignment with cosmics &
LHC beam induced particles
( see talk by Olivier Callot)
Events with LHC beam induced particles
OT
Calo
Muon
Side view Splashy event from lost particles (not all tracks reconstructed...)
12Split, 2 October 2008
Andreas Schopper
Extracting physics from (very) first dataExtracting physics from (very) first data
1E+00 1E+02 1E+04 1E+06 1E+08 1E+10 1E+12 1E+141E-10
1E-08
1E-06
1E-04
1E-02
1E+00
1E+02
σ∙ε/σmb
Nmb
π± production
Bd→J/ΨKs production
J/Ψ production D-meson production
Λbar production
K0 production
φ production
Λ production
π0 production
J/Ψ from bb
108 minimum bias @ 2kHz
Split, 2 October 2008
13Physics at LHC 2008
Exploit minimum bias data
S= σmb
σ∙ε∙Nmb
Number of selected signal events:
Andreas Schopper
Exploiting minimum bias dataExploiting minimum bias data
plenty of Ksππ and Λ→pπ 95% purity with kinematical and vertex cuts only clean & unbiased sample for PID studies study hadron identification performance
collect 1400 J/ use triggered J/ψ data with pt-cut on single muon
second muon unbiased for PID studies study muon identification performance search for DKπ, Kπππ, K0
Sππ, Kππ0
assess background levels, resolutions & relative efficiencies
demonstrate capability to reconstruct first final states
Split, 2 October 2008
Physics at LHC 2008 14
Λ→pπ
~ 40 mins @ 1031 cm-2 s-1
~50k Λ→pπ eventsin 108 minimum bias events
Andreas Schopper
Exploiting first muon trigger dataExploiting first muon trigger data
Split, 2 October 2008
Physics at LHC 2008 15
applying J/ψ trigger with pt-cut on single muon
expect ~106 J/ with 1 pb-1
Reconstruct J/ and disentangle fraction of prompt and detached J/’s
discriminating variable:
study proper time resolution with prompt component
Measure prompt J/ and bb cross section in a region not accessible to other collider experiments
PV
+
-
dz
Andreas Schopper
Exploiting ~5 pb-1 of data with full triggerExploiting ~5 pb-1 of data with full trigger
Split, 2 October 2008
Physics at LHC 2008 16
23k B0 D* tagging studies with flavour specific modes
3.2k B+J/K+
selection does not require lifetime cut unbiased lifetime distribution to determine resolution
4.3k B0 D-(K- π+π-) π +
measure B0 lifetime reach current precision (0.009 ps) with 60k events
trec
-ttrue
(fs)
(s t) ~34 fs
B0 D-(K- π+π-) π + Invariant mass ofBsJ/()
(~days of data taking)
3.7k B K*γ reference channel for all radiative loop decays
2.3k BJ/K* exercise fit machinery for analysis of BsJ/
Select first 285 BsJ/
σ(Bs)=13 MeV
~0.2 pb-1
B K*γ
Oscillation plot with 3 pb-1 of B0 D*
A(t
)
13 min. running
Andreas Schopper
Exploiting ~0.5 fb-1 of data with full triggerExploiting ~0.5 fb-1 of data with full trigger
Split, 2 October 2008
Physics at LHC 2008 17
(1/4 of a nominal year)
t,c,u
t,c,u
W W
s,d
b s,d
b
0B0B
+NP?
Θtr= angle between l+ and normal to decay plane
ηf = +, - 1 CP eigenstates
J/ is not a pure CP eigenstate (2 CP even, 1 CP odd amplitude) need to fit angular distributions of decay
final states as function of proper time
measure Bs-Bs mixing phase s in BsJ/(µµ)
with 28’500 reconstructed BsJ/(µµ) signal events (before tagging)
Sensitive to New Physics effects in mixing
s = s(SM) + s(NP)
in SM: s = – 2βs = –arg(Vts2) ~ –0.04
stat(s)~0.06 with 0.5 fb-1
Andreas SchopperPhysics at LHC 2008 18Split, 2 October 2008
Exploiting ~0.5 fb-1 of data with full triggerExploiting ~0.5 fb-1 of data with full trigger
Very rare loop decay, sensitive to New Physics BR ~ 3.510–9 in SM, can be strongly enhanced in SUSY Main issue is background rejection:
dominated by B+X, B-X decays good mass resolution and PID essential
LHCb expected performance: with 0.5 fb–1: exclude BR values down to SM value with 2 fb–1: 3 evidence of SM signal with 10 fb–1: > 5 observation of SM signal
W
W
b
s
t
?
?
MSSMCurrent limit from CDFBR(Bs) < 4.710-8
(1/4 of a nominal year) measure BR of rare decay Bs +–
Andreas Schopper
ConclusionConclusion
Split, 2 October 2008
Physics at LHC 2008 19
LHCb is a heavy flavour precision experiment searching for New Physics in CP-violation and rare decays
The experiment is ready for data taking with first collisions Very first data can be exploited to validate the expected
detector performance With fraction of a 1 years nominal data set LHCb can already
perform important key measurments probing New Physics