cherenkov detector 144 quartz bars k, π, p separation electromagnetic calorimeter 6580 csi crystals...
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Cherenkov Detector 144 quartz bars K, π, p separation
Electromagnetic Calorimeter6580 CsI crystals
e+ ID, π0 and γ reco
Drift Chamber40 layers
tracking + dE/dx
Instrumented Flux Return 12-18 layers of RPC/LST
μ ID
Silicon Vertex Tracker5 layers (double-sided Si sensors)vertexing + tracking (+ dE/dx)
e+ [3.1 GeV]
e- [9 GeV]
1.5T Magnet
The BaBar Detector
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Status of the Collaboration (Oct 2007)
74 Institutions in 10 countries
Although fewer babarians than last year, with more than 200 students and postdocs the collaboration continues to be on a very strong
foundation.
Faculty PhD Staff Postdoc Grad Non-PhD Totals
Canada 10 2 7 19
France 14 12 3 12 4 45
Germany 7 4 1 15 27
Italy 27 28 15 14 84
Netherlands 1 1 2
Norway 2 1 3
Russia 2 6 2 1 11
Spain 3 2 3 8
United Kingdom 18 1 12 12 1 44
United States 72 47 40 64 19 242
Totals 153 101 75 131 25 485
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z(vtx Breco) ~ 80mt(ps)+5-5 0
Silicon Vertex Tracker (SVT)
sin2 from B0(cc)K0
System management: Italy and US Software coordinator: Italian Operation managers: shared equally
between Italy (+Spain) and US
Responsabilities
double-sided silicon sensors 5 layers 150.000 readout channels provides vertexing, tracking
and dE/dx
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Drift Chamber (DCH)
Thin Al forwardendplate
Beryllium inner wall
• 40-layer small-cell chamber– 7104 drift cell formed from hexagonal wire
pattern
– 80&120m Al wires and 20m Tungsten sense wires
• Layer organized into superlayers– wire directions in axial-u-v pattern
• 80:20 helium:isobutane gas mixture– low-mass gas and small Lorentz angle
Average distance resolution in the cell is 120m
dE/dx resolution is 7.5-8.0%
Canada-France-Italy-US
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Detector of Internally Reflected Cherenkov light (DIRC)
>4 separationat 3 GeV/c
Cher. angle vs. momentum for pions and kaons
LAYOUTSIGNAL FORMATION
PERFORMANCE
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Electromagnetic Calorimeter (EMC)
• Tallium-doped CsI crystals
• Barrel: 5760 crystalsForward endcap: 820 crystals
• 16÷17 radiation lengths
• 16o<<142o polar angle coverage(90% in CM frame)
M(0) = 6÷7 MeV
Energy and angular resolutions: 0 reconstruction
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Instrumented Flux Return (IFR)• Absorber-detector alternating layers
for and KL detection:
– Bwd endcap: original RPC (18 layers);
– Fwd endcap: new RPC (16 layers) in streamer or avalanche mode;
– Barrel: old degraded RPC replaced by LST in summer 2004/2006 (12 layers)
• Italy + US teams – Detectors and read-out built in Italy
(both RPC and LST)
– System Managers: 1 Italy + 1 US for each subsystem;
– Operation Managers: 2/3 Italy + 1/3 US
-ID performance
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t =0We need to know the flavour of the B at a reference
t=0.
B 0
(4S)
The two mesons oscillate coherently : at any given
time, if one is a B0 the other is necessarily a B0
In this example, the tag-side meson decays first.
It decays semi-leptonically and the charge of the
lepton gives the flavour of the tag-side meson :
l = B 0 l = B 0. Kaon tags also used.
tagB 0l (e-, -) =0.56
z = t c rec
sK
t picoseconds later, the B 0 (or
perhaps it is now a B 0) decays.
B 0
ll
d0B b
W
At t=0 we know this
meson is B0
How time-dependent decay rates are measured
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Threshold kinematics: we know the initial energy of the Y(4S) system,
therefore we know the energy and magnitude of momentum of each B
2*2*BbeamES pEm **
beamB EEE
Background Background
(spherical)
(jet-structure)
Event topology
Signal Signal
Several analyses use an unbinned maximum likelihood fit to extract parameters of interest
Key analysis techniques
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Measurement of CKM angle Measure 180 – – = through time dep.
CP violation in buud decays Updated measurement with B
5.4 evidence of CPV in B0+-
Updated measurement of B BFs
Updated measurement with B Solution of isospin analysis consistent with
SM: =[73,117] @68% CL. uncertainty dominated by penguin pollution
Measurement of B()0 through Dalitz plot analysis Data prefers ~90o, no constraints at 95%CL
First ACP(t) measurement of Ba1(1260) Constraint on requires BFs of SU(3)-related
decays and is not available yet.
PRL99, 021603 (2007)PRD76, 091102 (2007)
PRD76, 052007 (2007)
WA B, , combination
PRL98, 181803 (2007)
PRD76, 012004 (2007)
Constraint on with B using isospinanalysis or isospin+SU(3) (shaded, see ref.)
BB 10 383 6
α = [80,107]o U [156,171]o @ 95% Prob.
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Measurement of CKM angle: β
J/Ks,(2)Ks,χc1KS, ηCKS (ηCP=-1)
J/KL (ηCP=+1)
018.0032.0714.02sin
PRD 76, 111102 (2007)
• Improved measurement of CP asymmetries in B0(cc)K(*)0
Average on all channels, theory error <1%
PRL 99, 171803 (2007)
• CP violation in B0D(*)+D(*)- Vector-vector final state angular analysis needed since CP content depends on angular momentum
the CP-even fraction is dominant
Evidence of CP violation at 3.7 CLResult consistent with B0(cc) K(*)0
BB 10 383 6
BB 10 386 6
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sin 2eff with bs qq penguins
Belle : ~540M BB
BaBar: ~350M BBBaBar still exploits its luminosity significantly better than Belle
SM contribution Possible NP in loops
B0’Ks
PRL 98, 031802 (2007)
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First measurements of B0D0K*0, D0Ks: Update of B-D0K- with D0CP eigenstates Measurement of sin(2+) with time dep. Dalitz plot analysis of
B0D-Ks+:
= arg[-VudVub*/VcdVcb*]
It is measured in the interference between B-D0K- and B-D0K-
Many D0 modes are measured to increasethe statistics Update of B-D(*)0K(*)-, D0Ks and KsKK
Measurement of CKM angle
o2223 )5576(
Updated world average
Moriond 08
(stat) (syst)(Dalitz Model)
Submitted to PRDarXiv:0804.2089
To be submitted to PRD-RC
f
f
To be submitted to PRD-RC
o)56162(
o)205383(2 arXiv:0712.3469, accepted by PRD
new measurements:= (81 ± 15)o
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Plep
>0.8GeV
1st moment (mean)
2ndmoment (width)
Measurement of |Vcb
|• Semileptonic Cabibbo favoured B→Xcℓ decays
allow to extract the magnitude of the CKM parameters V
cb: Experimental clean but good
understanding of QCD corrections is crucial
• Exclusive decays: B→D*ℓ, clean but need Form Factor normalization at zero recoil, F(1): (from Lattice QCD).
– Exploiting the full kinematics of the B→D*ℓ both the form factors ratios (R1, R2) and the F(1)*|Vub| parameter have been extracted
• Inclusive B→XℓMeasurements: Operator Product Expansion allows to extract V
cb exploiting
the fit to moments of many experimental quantities:– Moments of the hadronic mass distribution, and
moments of the lepton momentum distribution as function of the minimum lepton momentum
PRD77:032002, 2008F(1)|V
cb|·103=34.4±0.3
stat1.1
syst
Br=4.690.04stat
0.34syst
%|V
cb|·103=37.41.2
exp1.4F(1)
decay width d~|Vqb|2mb
5
|Vcb
|·103=41.88±0.81 (2% error)m
b=4.552±0.055 (1.2% error)
arXiv 0707.2670 (EPS07)Global fit using M
Xc and P
lep
moments from BaBar
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Measurement of |Vub
|• b→uℓ decays allow to extract |V
ub|:
– |Vub
|/|Vcb
| provides benchmark for testing New Physics in other processes
• Exclusive measurements:– B→ℓ using different technique: -reconstruction (high
efficiency but low S/N), tagged samples (low efficiency but good S/N). Need Form-Factors (lattice-QCD)
• Inclusive B→Xuℓmeasurements: large background
from b→cℓ Need to cut on q2, Mx, P
lep distribution (or
their combinations) to reduce thisbackground– need to understand QCD (theory), and b-quark motion inside
the B-meson: shape function (from spectra in b→s)
B→ℓ
Cut: |Vub
|·103
Plep
>2.0 GeV 4.440.25exp0.47
theo PRD73:012006,2006
Elep
, q2 3.950.26exp0.63
theo PRL95:111801,2005
mX
<1.55 GeV 4.270.20exp0.30
theo arXiv:0708.3702
P+ =E
x-|P
X| 3.880.25
exp0.24
theo arXiv:0708.3702
mX, q2 4.570.29
exp0.30
theo arXiv:0708.3702
-reco: PRL98:091801(2007)tagged: PRL97:211801(2006)
Around 10% uncertainty from single anlysis
b→uℓ b→cℓ
|Vub
|·103=4.1 0.3exp -0.4 FF(theo)
+0.6
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with 230 million of BB
Radiative Decays b→s• One loop process: sensitive to New
Physics spectrum in the recoil of a Breco
(almost no background for E>2.2 GeV)
– Br=(3.650.85)x10-4
• CP asymmetry (<1% in SM, up to 15% in some NP models). Xs from sum of 16 exclusive modes
- ACP=(-0.0120.030)
• Observation of the b→dtransition with B→
– Br(B→)=(1.10-0.330.37 0.09)x10-6
– Br(B→)=(0.790.200.22 0.06)x10-6
– Br(B→)=<0.78x10-6@90%CL
with 383million of BBwith 347million of BB
back
grou
nds
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• Standard Model
– BF~10-6
• Forward-Backward Asymmetry vs q2
– Kℓℓ is forward-backward symmetric if there are no new scalar operators
– Angular distribution of the lepton in the di-lepton system
– Constraints on the signs of the Wilson coefficients C7,C9,C10
– K* decay angle cos(K) gives longitudinal polarization FL
• Sensitive to C7 sign or new right-handed currents at low q2
BK(*)ℓℓ
Bl
l
s
q*K
lForward-backward asymmetry
383 million BB paper in preparation
K* longitudinal polarization
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Leptonic B Decays
,H
at 90 % CL (1.2±0.4
stat±0.4
syst)x10-4
combination of semileptonic and hadronic tags
< 5.6x10-6 < 5.2x10-6
1x10-4 4x10-7 O(10-12)
B B Be
Allows extraction of fBVub (fB given Vub)
SM predictions
-Technique: Reconstruct one B meson as either -BDℓX (X = , 0 or nothing) -BDxhadthe other B is searched for Bℓ, ℓ = , e
-e,helicity suppressed-Possible enhancement due to New Physics-Bconstraint on the plane tanβ vs Higgs boson mass
PRD76,052002(2007)
PRD77,011107(2008)
at 90 % CL
ArXiv: 0801.0697
submitted to PRD
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Charm Physics
• D mixing and CP violation:– Look for signs of new physics (x>>y or CP
violation)First evidence of D mixing in D0K+-
Decay modes under analysis: KS,KSKK,KK,,K3,K0
Limits on CP violation in KK, at O(0.1%) level
• Dalitz plot Analysis:– KS, KSKK, 0 are also important tools for
analysis
• Spectroscopy:– DsJ
* new resonances– New charm baryons– Measurements of spin
D0K+-: evidence of mixing at 3.9
. Best fit
+ :(,)No mixing
Contours at 1intervals
PRL 98:211802,2007
Fitted signal4030 88
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physics B-factories are also tau factories!
-lifetime measurements tests of CPT, lepton universality
-decays with strange quarks very precise measurement of |Vus|, ms
new decay modes via resonance observed
high multiplicity hadronic states rich resonance sub-structures in 3/5 prong
decays limits on decaying into 7/8 pions
direct searches for New Physics lepton flavor violation, lepton number
violation baryon number violation CP violation in lepton sector
B()<6.8 x 10-8 @90%CLB(e)<1.1 x 10-7 @90%CLsearch for into 3 leptons decay on 3.42 x 108 e+e-+- eventsB(ℓℓℓ)<3.7-8.0 x 10-8 @90%CL
search for e on 2.07 x 108 e+e-+- events
K
PRL100:011801,2008
Large improvements comparedto PDG in many relevant channels
and many other hhh decays
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– new states discovered; new interpretations
– improved measurements of resonance parameters
observation of enhanced Y(1S) for Y(4S): unexpected in ordinary
quarkonium picture.
• Interesting possibilities in bottomonium:– search for missing states;
– search for NP in Y(nS) decays.
J Y(3940)J/
B+
B0Combining BABAR and Belle: ~4 mass difference two X states?
DD
*
X(3872)
Important contributions:
Heavy-Quarkonium ResultsP
RD
77
, 0
11
10
2
arXiv:0711.2047
arX
iv:0
80
3.2
83
8
347/fb
383/fb
Moriond QCD
443/fb
347/fb
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ee Interactions via Initial State Radiation ee ISR ee ISR ISR X X is any allowed final state ( JPC = 1) Radiator function W(s,s) known to <1% (ee X) measured as a function of mX = s ee interactions accessible from threshold up to ~5 GeV)'().,'()'( 0 sssWs
dx
d
s’
Measure both exclusive and inclusive cross sections Measure R(s) = had(s)/(s) hadronic contribution to (g-2) and QED(Z0) Form factors, spectroscopy, new states discovery (e.g. Y(4260))
K+K- K0
SK0L
K+K-K+K-K+K-
K+K-K0K
J/
62K+4 (2S)
s' [GeV]
R U
nit
s
pp
Published Results Analyses in Progress
DD*
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Final Data Sample Total data collected until
September 2007:– 480M BB pairs,
– 630M cc events,
– 440M
Run 7 (Dec 07- Apr 08), collected:
– 30/fb at Y(3S) and
– 14/fb at Y(2S)
– Scan above the 4S
• Analysis of these data sets has started, results expected for summer'08
– Search for rare decays and detailed bottomonium spectroscopy
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sin2
~3.6% 8o
15o
ubV
~9%
B B->
B factories CKM reach today