Cherenkov Detector 144 quartz bars K, π, p separation Electromagnetic Calorimeter 6580 CsI crystals...
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Transcript of Cherenkov Detector 144 quartz bars K, π, p separation Electromagnetic Calorimeter 6580 CsI crystals...
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
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
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
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
Detector of Internally Reflected Cherenkov light (DIRC)
>4 separationat 3 GeV/c
Cher. angle vs. momentum for pions and kaons
LAYOUTSIGNAL FORMATION
PERFORMANCE
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
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
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
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
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.
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
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)
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
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
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
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
• 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
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
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
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
– 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
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*
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
sin2
~3.6% 8o
15o
ubV
~9%
B B->
B factories CKM reach today