Download FPCP, Paris 2

The LHCb experiment:
status and physics program
Clara Matteuzzi
On behalf of the LHCb collaboration
Università Milano-Bicocca and I.N.F.N. Milano
FPCP Paris, 2-6 June 2003
Clara Matteuzzi
FPCP, Paris 2-6 june 2003
The LHCb experiment
LHCb is a forward one-arm
spectrometer dedicated mainly to
study CP violation and rare B decays
at LHC
Check consistency of the Standard Model :
precision measurements of angles and sides
of the CKM triangle
Search for New Physics :
rare and SM forbidden decays of b particles
Clara Matteuzzi
FPCP, Paris 2-6 june 2003
Present status
The triangle
Consistency of the Standard Model (assumed to
determine the vertex) and the direct measurement
of sin2β from B-factories
|Vcb| from BHcX decays  A
|Vub| from BHuln decays  r2+h2
Bd-Bd mixing, Dmd  (1-r)2+h2
Clara Matteuzzi
BdJ/yKS
Bdpp
BsJ/yf
B s  D sK
FPCP, Paris 2-6 june 2003
New physics
Db = 1: Decays
through penguin
b
Db = 2 : Oscillations
through box
b
d,s
new
particles
d, s
new
particles
b
through tree
d,s
d, s
b
l
or
l
d, s
new
particles
l
or
b
l
The Standard Model tree process not affected.
Clara Matteuzzi
FPCP, Paris 2-6 june 2003
b at the LHC machine
Ecm
(IP1,IP5)
14 TeV
L(cm-2 s-1)
2x
s (bb)
s (inel)
500 mb
80 mb
#bb-pairs
b fraction
f
t bunch
z primary
inter/xing
1012 /year
5 x 10-3
40 MHz
25 ns
5 cm
0.4
(2-20)
Clara Matteuzzi
1032
(10-100)
Luminosity
locally controlled
All types of b-hadrons
Bu , Bd , Bs , Bc , Lb , Sb , Xb,...
with large boost of the hadron
FPCP, Paris 2-6 june 2003
b
- physics at LHC
Crucial tasks of a detector:
triggering
particle ID
(K/p/p/e/m)
identification of exclusive final states
tagging
background rejection
decay time resolution
Clara Matteuzzi
FPCP, Paris 2-6 june 2003
Aperture Dipole
~ 15 –magnet
300 (250): mrad
The
1.5 < |
Outer Tracker
LHCb detector layout
trapezoidal coils
h |•• Warm
< 3.5
pole shape following
Inner the
Tracker
acceptance
 3 stations 4 layers each
•  Bdl = 4 Tm
 3 stations with 4 double
• P layers
= 4.2 MW 320 μm thin silicon
 5 mm straws tubes
 198 μm readout pitch.
 Fast drift gas (signal within 50 ns)
 130k readout channels.
75% Ar 15%CF410%CO2
50k readout channels.
m chambers
MWPCs
~65
~1.41.2
m2 m 2
Ecal
70% modules produced
Hcal (Shashlik
15% modules
produced)
type
(66layers 2mm Pb/4mm scintillator)
Fe + scintillator tiles
Transverse granularity 4,6,12 cm cells
1468 cells, 5.6 lI
~6000 channels , 25 Xo
40% Xo , 12% σ/E
lI ~ 75% / sqrt(E)
Clara Matteuzzi
σ/E ~ 10%/sqrt(E)
FPCP, Paris 2-6 june 2003
The LHCb Vertex Locator
 low occupancy
 Si area : 0.32 m2
 #Xo : 0.18
 st
: 43 fs
 # channels : 172 k
s IP
21 stations
32 m m
 17 m m +
pT
Clara Matteuzzi
FPCP, Paris 2-6 june 2003
Tracking performance
Average efficiency = 92 %
Efficiency for p>5GeV >95%
Ghost rate pT>0.5 GeV ~ 7%.
Mass resolution
(~13 MeV)
for the decay channel
Momentum resolution:
Dp/p=0.38%
<N> = 27 tracks/event
Proper time
resolution (42 fs)
Bs  Ds p+
KKπ
Clara Matteuzzi
FPCP, Paris 2-6 june 2003
The RICH of LHCb
2
detectors with 3 radiators
(aerogel, C4F10, CF4)
cover momentum range:
2 - 100 GeV
K-p separation
RICH 1
(25-300 mrad)
Clara Matteuzzi
5 cm aerogel
4 m3 C4F10
RICH 2
(15-120 mrad)
100 m3 CF4
FPCP, Paris 2-6 june 2003
Physics with Particle Identification
Bs
Ds K
Bs
K+KPurity=13%
Purity=7.0%
Purity=66%
efficiency=88%
Clara Matteuzzi
Purity=84%
Efficiency=79%
FPCP, Paris 2-6 june 2003
subdetectors
Level-0
Calorimeters
Muon
Pile-up veto
Level-1
VELO
Trigger Tracker
Level-0
Higher Levels
all the
detector
data log
Clara Matteuzzi
LHCb Trigger
40 MHz pT of e, m, h ,g
1 MHz
Impact parameter
Rough p estimate
( ~20%)
40 KHz
final state
reconstruction
200 Hz
FPCP, Paris 2-6 june 2003
LHCb L1 trigger
Performance in B decays
 trigger robust and flexible
 hadron trigger fundamental
for hadronic final states
 trigger efficiencies L0xL1
20 % - 70%
Clara Matteuzzi
FPCP, Paris 2-6 june 2003
Simulated bb events
MC Pythia 6.2 tuned on CDF and UA5 data
Multiple pp interactions and spill-over effects included
Complete description of material from TDRs
Individual detector responses tuned on test beam results
Complete pattern recognition in reconstruction
Clara Matteuzzi
FPCP, Paris 2-6 june 2003
Event yield in LHCb
1 year = 2 fb
Yield calculated taking
into account :
-1
(L = 2x1032 cm–2s-1)
Channel
Yield
B0  p+p-
27 k
B0  K+ p-
115 k
B s  K+ K-
35 k
 L0 and L1trigger efficiencies
(including pile-up veto)
Bs Ds-p+
72 k
 Reconstruction efficiencies
(tracking, calorimeters, PID)
Bs J/y (m-m+ )f
109 k
Bs J/y (e-e+ )f
19 k
B0 J/y(m-m+) KS
119 k
 Geometrical acceptance,
detection efficiency, material
 Selection cuts efficiency to identify
the final state
Bs Ds-K+
B0K0* g
8k
20 k
more background simulated events are necessary
to optimize selection criteria vs background rejection
Clara Matteuzzi
FPCP, Paris 2-6 june 2003
Measuring
g
4 ways of determining g
 Time dependent analysis of BsD+sK- (tagged)
 Rate difference between B-DoK- and B+DoK+ (untagged)
model independent
 Rate measurements in Kop and Kp (Fleisher-Mannel) or rates
in Kop and asymmetry in Kpo (Neubert-Rosner, Beneke et al) .
 Measure time dependent asymmetries in (Fleischer,Martinelli)
Bop+p- and BsK+K- symmetric d
s
dependence on hadronic assumptions in the
different calculations
Clara Matteuzzi
FPCP, Paris 2-6 june 2003
Measuring
 must be separated from
(~15 times larger Br)
Bs  Ds
g
–p+
with Bs  Ds±K+
Bs vtx resolution (mm)
 hadronic trigger, K/π separation, proper time
resolution are fundamental
 gets g-2dg
(needs 2dg from Bs –>J/Ψ Φ )
 In one year of data (2 fb-1)
8k Ds K and 72k Ds π
Ds mass resolution (GeV)
expected sensitivity:
Dms = 20 ps–1
for Dms = 30 ps–1
s(g) ~ 100 for
s(g) ~ 120
depending on amplitudes, strong phases, γ, Δms, ΔΓ/Γ
Bs  Ds–p+ measure Bs oscillations
Clara Matteuzzi
Δms up to ~ 60 ps-1
FPCP, Paris 2-6 june 2003
Study of
B0
s
 J/y f
(mm K+K–)
 CP asymmetries determine –2δγ (very small in Standard
Model but sensitive to New Physics). And also Δms and ΔΓs
 Must be separated from prompt J/Ψ production
(possible with 0.1 < B/S < 0.4 at 90% CL )
prompt J/y(mm) background
Clara Matteuzzi
B0s  J/y(mm) f signal
FPCP, Paris 2-6 june 2003
Study of
B0
s
 J/y f
(mm K+K–)
 Needs angular analysis to disantangle CP-odd
and CP-even states
 In one year of data (2 fb-1)
109k J/Ψ Φ and 19k J/Ψ Φ
(mm)
(ee)
expected sensitivity:
σ(2δγ) ~ 20 for
also B0s  ΦΦ
B0s  J/Ψ η
Dms = 20 ps–1
B0s  ηcΦ probe δγ
(under study in LHCb)
Clara Matteuzzi
FPCP, Paris 2-6 june 2003
Measuring
g
with B(s)  p p, K p, K K
 Relies on hadronic trigger, excellent K/π
separation, mass resolution
 Select B candidates with pT, IP/σ, L, mass cuts
 Combinatorial bb bckgr. can be rejected (S/B > 1)
92% purity
B0 p+p-
96% purity
B0 K+p-
σ(γ) ~ 30 for
Clara Matteuzzi
98% purity
B0s K+K-
xs = 20
FPCP, Paris 2-6 june 2003
Present estimate of LHCb Physics reach
These numbers are being updated, and more channels studied,
in the re-optimization of the LHCb detector to be concluded in
September 2003
2 fb–1
1 year data
Channel
b
Bd  J/y Ks
g
Bs  Ds K
Bd  pp, Bs  KK
Yield
Precision
119 k
s(b)  0.6o
8k
27 k, 35 k
s(g) 10o
s(g)  3o
a
2dg
Bd  p+p-
27 k
s(a)  5o- 10o
Bs  J/y f
128 k
s(2dg)  2o
|Vtd/Vts|
Bs  Ds p
72 k
Dms up to 58 ps-1
rare decays Bd  K* g
20 k
Clara Matteuzzi
FPCP, Paris 2-6 june 2003
Conclusions
The present of b-physics is already very rich
B-factories (BaBar, Belle, CLEO), Tevatron,
+ (LEP, SLC)
The future :
Next generations of dedicated experiments at hadron machines
will have order of 1012 bb pairs per year with
dedicated trigger and particle ID
LHCb is a unique opportunity to measure precisely angles
and sides of the CP triangle and to understand the origin of
CP violation in the SM and beyond
LHCb installation starts in 2005
data taking starts in 2007
Clara Matteuzzi
FPCP, Paris 2-6 june 2003
Back-up slides
Clara Matteuzzi
FPCP, Paris 2-6 june 2003
LHCb TRIGGER
channel
L0 (%)
m e h g
B0s  J/y(mm) f 90 5 30 3
B0s  J/y(ee) f 7 36 24 4
B0s  Ds K
8 5 37 2
6 28 30 47
B0d  K* g
7 9 55 3
B0d  p + p–
Clara Matteuzzi
all
93
52
44
82
61
L1(%) Total
(%)
73
68
43
23
65
29
33
27
51
31
FPCP, Paris 2-6 june 2003