Status of the LHCb Experiment LHCb RRB at CERN 25 October 2006
The LHCb Experiment
description
Transcript of The LHCb Experiment
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The LHCb Experiment
• The search for New Physics • The LHCb experiment• LHCb start-up and the physics
programme
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Current StatusFirst generation B factories (BaBar@PEPII and Belle@KEKB), together with CDF/D0@Tevatron, have a spectacular physics record
PDG 2000
PDG 2006
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Tests of CKM picture• Unitarity triangle from tree-level processes only
• Observe CP violation in CKM matrix is at work !
• Tree processes not affected by New Physics
• Constraint must be satisfied by any New Physics• Requires a precision measurement of
cbub V,Vb c,u
W
cbub VV
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Current tests indicate that the SM description of CP is successful and any New Physics will appear as a small correction
Tests of CKM picture• Allowed region from CP conserving
quantities
• Compared to region from CP violating quantities
• CKM phase is dominant
• New Physics is not excluded
s,dcbub mm,VV
,,,K
031.0387.0
041.0171.0
026.0675.02sin039.0764.02sin
UT sides
Measurement (bccs)2.3
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New Physics• SM cannot be ultimate theory
– low-energy effective theory of a more fundamental theory at a higher energy scale (TeV range)
– Hierarchy problem: New Physics required to cancel radiative corrections to the Higgs mass but leave the SM EW predictions unaffected
• How can New Physics be discovered and studied ? – NP models introduce new particles which could
be produced and discovered as real particles at the LHCappear as virtual particles in loop processes observable deviations from the SM expectations in flavour physics and CP
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• NP needs to have a flavour structure to provide the suppression mechanism for FCNC processes already observed.
• Once NP is discovered it is important to measure this flavour structure (including new phases) and to distinguish between the NP models.
• Direct and Indirect approaches are very complementary
t,c,u
t,c,u
W W
s,d
b s,d
b
0B 0B
Box diagram
New Physics
0B,K0
s
b
s,ds
s,d
ss
Penguin diagram
2Varg,2Varg
Vm2ts
SMs
2td
SMd
2ts,td
SM
??New Physics
d
m
s
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New Physics in B0 Mixing• Use a model independent parameterization of
New Physics in B0 (and K0) mixing
– includes only SM box diagrams– includes NP contributions as well
• Four independent observables
• One additional parameter for K0 mixing
0q
SMeff
0q
0q
fulleff
0qi2
BBHB
BHBeC qB
q
s,dq
SMeffHfulleffH
0SMeff
00fulleff
0 KHKImKHKImCK
,With NPallowed
NP in D0 mixing is neglected
5 NP parameters
ssdd BBBB ,C,,C 0,1C
qq BB (SM)
Reiterates need for precisionmeasurement of
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New Physics in B0 Mixing
Non-zero central value of d from difference in SM fit between angles (sin2) and sides (Vub)
CBs constrained more than CBd from CDF measurement of ms
Need to measure Bs mixing phase s
0dB
SM
0sB
SM
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Search for New Physics • Measure processes very suppressed in SM
– CP in Bs mixing ( in SM)• BsJ/
– Radiative and very rare B decays • BdK*, Bs, Bd K*, Bd,s
– Rare D decays and D0 mixing– Lepton flavour violating decays
• Precision measurements of CKM elements– Bs oscillations– Compare pure tree level processes with processes sensitive to NP
• Sin2BdJ/Ks vs BdKs • BDK vs B/KK
– Measure all angles and sides in many different ways. Any inconsistency will be evidence for NP
– Requires clean and improved theory predictions
2s 2
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The LHCb Experiment• LHCb is dedicated to the Search for New Physics in
CP violation and Rare B decays
• LHCb Collaboration: 14 countries, 47 institutions, ~600 people
Interactionpoint
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LHCInteraction point 8 Final focus
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Muon Calorimeters RICH2Trackers
Magnet
RICH1VELO
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b production at the LHCIn the forward region (4.9 > >1.9):• bb cross-section large (~230 b)
• Luminosity ℒ=2x1032 cm-2s-1
1012 B hadrons in 107 sec• All species of B hadrons produced
(B, Bd, Bs, Bc, b-baryons)
• B’s have large momentum <pB>acc ~ 80 GeV/c Mean flight path of B’s ~7mm.
• bb production correlated and sharply peaked forward-backward. bb
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Trigger• Trigger crucial to the successful operation of LHCb
– B fraction is only ~1% of inelastic cross-section.– Br’s of interesting B decays <10-4
– Properties of minimum bias similar to B’s
• First Level Trigger (L0) – Hardware (custom boards, 4s latency)– Largest ET hadron, e() and (di-)– Pile-up system (not for trigger)– Reduces 10 MHz inelastic rate to 1MHz
L0 e
ffici
ency
(%)
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Trigger• High Level Triggers
– Software trigger run on CPU farm (1800 nodes)– Access to all detector data – Use more tracking information to re-confirm L0 decision – Full event reconstruction; inclusive and exclusive
selections tuned to specific final states– Output rate 2 kHz, 35 kB per event
Output rate Trigger Type Physics Use200 Hz Exclusive B candidates Specific final
states600 Hz High Mass di-muons J/, bJ/X300 Hz D* Candidates Charm,
calibrations900 Hz Inclusive b (e.g. b) B data miningTotal 2000 Hz
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Flavour Tagging
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VELO• 21 VELO stations (r and silicon
sensors)• Placed in a secondary vacuum vessel• 3cm separation, 8mm from beam • Separated by a 300 m of Al RF foil • Detector halves retractable for
injection
pile-up veto
RF foil
interaction point
Silicon sensors
~1 m
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VELO
RF foil
Vacuum vessel
Beam’s eye view
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VELO• 42 VELO modules
– r and layer – n+n type– 2048 strips/sensor– Strip pitch 40 m to 100 m
VELO module production
• Status– 70% modules produced – One half VELO complete
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Tracking
Trigger TrackerSilicon stripspT information for trigger
Outer TrackerStraw tubes
Inner TrackerSilicon strips2% of area20% of tracks
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Tracking
Trigger Tracker
Outer Tracker
Inner Tracker
Status: – Module production ~finished (IT end Feb)– Installation: OT finish Mar 07 IT/TT Mar-Jul 07
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Magnet
B/B = 0.03%B/B = 0.03%
Peak field on axis: 1.1 TField integral: 4 Tm (over 10 m)
By /T
z /cm
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Tracking performance• Track fit: bi-directional Kalman fit• Tracking efficiency >95% • Ghost rate <7% p > 12 GeV
p distribution for B tracks
Momentum Resolution
1/pt distribution for B tracks
Impact Parameter Resolution
VELOMagnet
T StationsTT
Event display
• Vertex resolution– ~10 m in x,y; 50 m in z
• Proper time resolution ~ 40 fs• B Mass resolution ~ 15 MeV
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RICH Detectors• Particle ID: p~1-100 GeV provided by 2 RICH
detectors
RICH1
RICH2
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• Status: RICH2 installed RICH1 finish installation Aug 2007
RICH Detectors• 3 radiators: RICH1 Aerogel (2-10 GeV), C4F10 (10-
60 GeV) RICH2 CF4 (16-100 GeV)
Aerogel22 tiles
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RICH Photodetectors• 484 Hybrid Photo Detectors (HPD’s)
80mm
120m
m
<QE> @ 270 nm (per batch)
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26
27
28
29
30
31
32
33
34
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16batch no.
aver
age
QE [%
] .
<QE> per batch
running <QE> (batch 1-16)
Quantum Efficiency
contract spec.typical 23.3 %
HPD production expected to be completed March 2007
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RICH Performance Full MC simulation using “global” fit to Cherenkov rings
High Level Trigger D* stream D*→D0(K) RICH independent E
ffici
ency
D* MC Truth
/K selected from D* sample(no MC truth)
RICH1 RICH2
Effi
cien
cy(%
)
p (GeV)
K or p
K K or p
Averages:K→ K,p eff: 83.1± 0.1%→misID
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CalorimetersSPD/PS: Pb/Scint., 2.5 X0
ECAL: Pb-Scint. Shashlik, 25 X0
HCAL: Fe/Scint. tiles, 5.6 0
%1E%10
EE
%10E%80
EE
ECAL
HCAL
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reconstructionExample: Time dependent Dalitz plot analysis of B0
14k signal events in 2 fb-1
Resolved π0
2 isolated photons
~15 MeV~10 MeV
Merged π0
Single ECAL cluster
MergedResolved
Transverse energy (GeV)
Efficiency = 53% for B0
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Muons• 1368 MWPCs (M2-M5, outer M1
region)• 24 3-GEMs (inner M1 region)
3-GEM
MWPC
M5
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Muons• Status: production finished;
installation and commissioning in progress
• ODE electronics under commissioning
Fixing chambers on the inner edge of wall requires expert climbers
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Muon ID• Muons at L0
trigger (pt > 1 GeV): AND of hits in the 5 stations
Bsμμ
μ
Tracking system
Muon system
Distance of closest hit (pad unit)
DC06 performance: ε(muons) = 90.5 0.1 %Total misID = 1.78 0.1 %misID for hadrons = 0.52 0.01 %Fraction of decays in flight = 72%misID for decays in flight = 43.1 0.2 %
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LHCb Status• LHCb is confident that the experiment will be
ready for data-taking in March 2008
• All major and heavy structures are installed• OT, RICH2, ECAL and HCAL are very close to be
ready for a “global” commissioning • RICH1, VELO, IT and TT needs still some (but
short) installation work.• Installation of Muon system and PS/SPD cabling
will still continue for a few months
• LHCb will take physics data in 2008 with a complete detector
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LHCb startup programme
• 2008: early phase– Complete commissioning of detector and trigger at s=14 TeV– Calibrate momentum, energy and particle ID– Start first physics data taking, assume ~ 0.5 fb–1
– Establish physics analyses, understand performance– Look asap for New Physics with measurements competitive at low
lumi
• 2009–20xx: stable running– Stable running, assume ~ 2 fb–1/year– Develop full physics program– Exploit statistics, work on systematics
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Very Rare B Decays: Bs +–
• Very rare loop decay, sensitive to New Physics:
– BR ~3.510–9 in SM, can be strongly enhanced in SUSY
– Current 90% CL limit from CDF+D0 with 1 fb–1 is ~20 times SM
W
W
b
s
t
?
?
MSSM • Main issue is background
rejection– With limited MC statistics,
indication that main background is b, b
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Very Rare B Decays: Bs +–
0.05 fb–1 overtake CDF+D00.5 fb–1 exclude BR values down to SM
2 fb–1 3 evidence of SM signal10 fb–1 >5 observation of SM signal
Integrated luminosity (fb–1)Limit at 90% C.L. (only bkg is observed)
Integrated Luminosity (fb-1)
Uncertainty in bkg prediction
Expected final CDF+D0 Limit
BR
(x10
–9)
SM prediction
LHCb Sensitivity(signal+bkg is observed)
Integrated Luminosity (fb-1)
5
3
SM prediction
BR
(x10
–9)
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Rare B Decays: B0 K*0
• Suppressed by loop decay, BR ~1.210–6
Forward-backward asymmetry AFB(s) in the rest-frame is sensitive probe of New Physics
• Sensitivity
– 7.7k signal events/2fb–1, Bbb/S = 0.4 ± 0.1
– After 2 fb–1, zero of AFB(s) to ±0.52 GeV2
determine ratio of Wilson coefficients
C7eff/C9
eff with 13% stat error (SM)
s = (m)2 [GeV2]
AFB(s), theory
+
–
AFB(s), fast MC, 2 fb–1
s = (m)2 [GeV2]
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• Bs mixing phase, s is very small in SM sSM = –
0.037 ± 0.002 (UT fits) – Could be much larger if New Physics in the box
•Golden bccs mode is Bs J/:– Angular analysis needed to separate CP-even
and CP-odd contributions– Expect ~130k Bs J/() signal events/2fb–1
(before tagging), S/Bbb= 8
•Add pure CP modes (J/(’), c, DsDs) – No angular analysis, smaller statistics
•Sensitivity:
Bs Mixing Phase s with bccs
[LHCb-2006-047]
stat(s) = 0.044 with 0.5 fb–1
? t,c,u
t,c,u
W W
s,d
b s,d
b
0B 0B
Channels s [rad]0.1420.1330.1090.108
Combined (pure CP eigenstates)
0.060
0.023Combined (all CP eigenstates)
0.022
0s /JB
sss DDB /JBs
csB
/JBs
Statistical sensitivities on s for 2 fb–1
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Constraints on New Physics in Bs mixing from s measurement
• New Physics in Bs mixing amplitude parametrized with and
• Can exclude already significant region of allowed phase space with the very first data (2008)
? t,c,u
t,c,u
W W
s,d
b s,d
b
0B 0B
NPsi2
SMs
NPs
0s
SMeff
0s
0s
fulleff
0s
eAA1
BHB
BHB
SMs
NPs AA NP
S
In April 2006, including CDF’s first measurementof ms
>90% CL
>32% CL>5% CL
After LHCb measurement of s with (s)= ±0.1 (~ 0.2 fb–1)
courtesy Z.Ligeti
NPS
SMs
NPs AA
from hep-ph/0604112
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bsss hadronic penguin decaysCurrently explored at B factories with time-
dependent analyses oftagged decays to CP eigenstates such as B0 KS,
etc.– Expect same result (i.e. sin2) as
b ccs tree decays like B0 J/KS if only SM Decay phase = 0
Decay phase ~ 0 in SMDecay phase ≠ 0 if NP
total phase = (mixing phase 2) + (decay phase)
b
c
s
c
W –VcbVcs
*
b
t
s
s
s
W –Vtb Vts*
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bsss hadronic penguin decays• Also accessible at LHCb
• Best channel is Bs
– CP violation < 1% in SM (Vts enters both in mixing and decay amplitudes)
– significant CP-violating phase can only be due to New Physics– Angular analysis required– 4k signal events per 2 fb–1 (if BR=1.410–5), 0.4 < B/S < 2.1
@90%CL
• After 10 fb–1
– ± 0.042 from Bs
– ± 0.14 from B0 KS (4k signal events, B/S < 2.4 @ 90% CL)
0sB
b
s ssss? NP
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CKM angleMany ways to measure at LHCb using various methods:•Tree-level processes
– Bs DsK ~14o per 2fb-1
– Bd D(*)
– B, Bd D(*)K(*), with D0 decaying to:2 bodies: K, KK, best modes offer 5-10o 3 bodies: KS KS KK, KS Keach per 2 fb-1
4 bodies: KKK
•Penguin processes– Bd
+–Bs K+K–
– U-spin approach ~ 4o per 2 fb-1
(7-10o with 20% U-spin violation) invariant mass
With PID With PID
KK invariant mass
Expect with 10 fb-1
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CKM angle
from BDK at LHCb (10 fb–1)
Two possible scenarios
loops (2006)
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Effect of LHCb on UT
%7.4/)(%17/)(
Summer 2006
%7.1/)(%5.3/)(
LHCb at L=10fb-1
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B mode (tree)
D mode Method (), 2 fb–1
B+ DK+ K + KK/ + K3
ADS+GLW 5º–15º
B+ D*K+ K ADS+GLW Under study
B+ DK+ KS Dalitz 8ºB+ DK+ KK 4-body
“Dalitz”15º
B+ DK+ K 4-body “Dalitz”
Under study
B0 DK*0 K + KK + ADS+GLW 7º–10ºB0 DK*0 KS Dalitz Under
studyBs DsK KK tagged, A(t) 13º
B modes (penguin) Method Assumption (), 2 fb–1
B0 +–Bs K+K–
tagged, A(t)Fleischer
Perfect U-spin symmetryUp to ~20% violation
4º7º–10º
Sensitivities to CKM angle
Signal only
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from B± DK±
• “ADS+GLW” strategy:– Measure the relative rates of B– DK– and B+ DK+ decays with neutral
D’s observed in final states such as: K–+ and K+–, K–+–+ and K+–+–, K+K–
– These depend on:• Relative magnitude, weak phase and strong phase between B– D0K– and B–
D0K– • Relative magnitudes (known) and strong phases between D0 K–+ and D0
K–+,and between D0 K–+–+ and D0 K–+–+
– Can solve for all unknowns, including the weak phase :
u
b
u
s
c
u
B–
D 0
K–
colour-suppressed
u
u
b
c
u
s
B–
D0
K–
colour-allowedWeak phase difference = Magnitude ratio = rB ~ 0.08
Decay 2 fb–1 yield
Bbb/S
B– (K–+)D K– 28k ~0.6
B+ (K+–)D K+ 28k ~0.6
B– (K+–)D K– 180 4.3B+ (K–+)D K+ 530 1.5
() = 5–15 with 2 fb–1
(depending on the strong phases)
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CKM 2008 (pre-LHCb)Improvements due to• Bd, B sector: B-factories (Babar/Belle)
– Assume ℒ = 2 ab-1 at the (4S) () 6.5°, () 6.5°, (sin2) 0.017
• Bs sector: Tevatron (CDF/D0)– Assume (2x) 6 fb-1 (s) 0.2, (s/s) 0.04, (ms) 0.5%
• Lattice QCD prospects%3.3/)(%4.7/)(
Now Pre-LHCb
6 TFlop year
201040 TFlop
year
20141 PFlop
year11% 5% 4% 2%13% 5% 4% 2%5% 3% 2.5% 1.5%
Vub-excl.* 11% 6% 5% 3%Vcb-excl.* 4% 2% 1.5% 1%
KB̂
BsBs B̂f Courtesy V.Vagnoni
CKM 2006, Nagoya
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LHCb Sensitivities with 2fb-1