Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://qfthep.sinp.msu.ru/talks/QFTHEP2010_Golubev.pdf Äàòà èçìåíåíèÿ: Tue Sep 14 09:13:20 2010 Äàòà èíäåêñèðîâàíèÿ: Mon Oct 1 19:46:02 2012 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: m 5

New Results from BABAR

Vladimir Golubev
Budker Institute of Nuclear Physics, Novosibirsk, Russia (for the BaBar Collaboration)

QFTHEP'2010 Golitsyno, Moscow, September 8­15, 2010
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Outline
n n

BABAR detector Evidence for direct CP violation in the measurement of the CKM angle with BFD(*)K(*)F decays Semileptonic bc l decays Semileptonic bu l decays Measurement of bd , bs , and |Vtd/Vts| Study of two-photon production of pseudoscalar mesons

n n n n

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BABAR Detector
E / E = 3.0%/ 4 E(GeV) 1.3%
6580 CsI(Tl) crystals 3 /K separation at 3 GeV/c

144 fused silica bars, 11000 PMTs

40 stereo layers

iron / RPCs, LSTs

5 layers, double sided strips 50 µm vertex resolution, 110 µm z separation for B decays

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BABAR Detector
Final BABAR dataset: N((4S)BB) = 470106 Off Peak Luminosity 53.85 fb N((3S)) = 122106 N((2S)) = 100106

-1

PEP-II peak luminosity 12.1 1033 cm-2s-1

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CKM angle
n

n

n

The CKM angle is the only CP-violation parameter, which can be cleanly determined from tree-level B-meson decays. Its precise determination is an important goal of present and future experiments in flavor physics The angle can be determined using BFDKF decays using interference between color-favored B-D0K- and color-suppressed B- D0K- decays with D0 and D0 decays to a common final state New BABAR results [arXiv:1005.1096] are based on Dalitz-plot analysis of eight decay modes for each B-meson sign: B±DK±, B±D* [D0]K± , B±D* [D]K±, and B±DK*± final states with DKS+-, KSK+K- full statistics of 468 million BB pares

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CKM angle from BDK decays
A

ub

A

cb

· Use common final states for D0 and D0 · Largely unaffected by New Physics · Clear theoretical interpretation of observables in terms of · Difficulty: small BFs due to CKM suppresion (10-5-10-7, so not many events) and rB=|Aub|/|Acb| is small due to further CKM and color suppressions (small interference) · All measurements are statistically limited

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CKM angle from BDK decays
Analysis methods for charged BD(*)0 K(*) (rB0.1)
§ GLW [1]: D0 decay final states: CP-even: K+K-, +-, and CP-odd:

KS 0, KS , KSf

§ ADS [2]: D0 decay final states: K+-, K+-0, K+-+- and CP-conj § Dalitz-plot [3]: D0 decay final states: 0+-, KS +-, KSK+K
-

[1] Gronau, London, Wyler, PLB 253, 483 (1991); PLB 265, 172 (1991) [2] Atwood, Dunietz, Soni, PRL 78, 3357 (1997) [3] Giri, Grossman, Soffer, Zupan, PRD 68, 054018 (2003);

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from BDK decays Dalitz-plot method
D 0 K S +
Decay amplitudes
-

(no D-mix nor CPV)
S
-

rB=|A(bu)|/|A(b c)|

S A( B - [ K S + - ]K - ) S m m 2 ( K S m )

D K S +

0

-

-

+ rB e
bc D K S +
0
-

-i + i

B


-

S
-

+

S A( B + [ K S + - ]K + ) Interference terms in decay rates are proportional to xm = rB cos( B m ) F ym = rB sin( B m )

B -strong phase difference between A(bu) and A(bc)

bu S+ D K S +
0

S

-

+ rB e
bc
S
+

+ i + i

B

bu

S


+

it for xF and yF is done for each decay mode

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Evidence for direct CP violation in the measurement of the CKM angle with BFD(*)K(*)Fdecays: D Dalitz-plot method
arXiv:1005.1096. Sub. to Phys. Rev. Lett.

B-DK-

B-D*K-

B+D*K+

B+DK+

Differences between B+ and B give information on

-

B-DK*B+DK*+
3.5 significance of CPV 9

(mod 180°) = ( 68 ± 14(stat) ± 4(syst) ± 3(mod) )°
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Evidence for direct CP violation in the measurement of the CKM angle with BFD(*)K(*)Fdecays: GLW method

· ·
R

arXiv:1007.0504. Reconstruct B±DK± final states with DK+K-,+- (CP even) and Sub. to Phys. Rev. D DKS0,KS,KS (CP odd) (five different final states for each B charge) Extract signal yields fitting directly to observables R
± K /

± K/

,R

K/

, and AC

P±
0 0

( B - DCP ± K - ) + ( B + DCP ± K + ) = ; - - + + ( B DCP ± ) + ( B DCP ± )

R

K /

=

( B - D 0 K - ) + ( B + D K + ) ( B - D 0 - ) + ( B + D + )
( B - DCP ± K - ) + ( B + D ( B - D 0 K - ) + ( B + D K )
CP ± 0 +

ACP

±

( B - DCP ± K - ) - ( B + DCP ± K + ) = ; - - + + ( B DCP ± K ) + ( B DCP ± K )
Results: ACP+= 0.25±0.06(stat)±0.02(syst) ACP-=-0.09±0.07(stat)±0.02(syst) RCP+= 1.18±0.09(stat)±0.05(syst) RCP-= 1.07±0.08(stat)±0.04(syst)

RCP± = 2

K+)

RCP

±

Significance of CPV in B± DK± from ACP+ is 3.6 , which constitutes first evidence for direct CP violation in B DK decays
x- - x+ (Dalitz) = 0.163 ± 0.055 x- - x+ (GLW) = 0.189 ± 0.062
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± RK RK

/ /

x± =

1 [RCP+ (1 m ACP + ) - RCP- (1 m ACP- ) 4

]

(3.0 ) (3.1 )
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Evidence for direct CP violation in the measurement of the CKM angle combined Dalitz-plot and GLW method results
(mod180°) = ( 68 ± 14(stat) ± 4(syst) ± 3(model))°
rB ( DK ) = 0.096 ± 0.029
* rB ( D* K ) = 0.133+ - 0.042 0.039 + 0.066 - 0.062

rS ( DK * ) = 0.149

(mod 180 ° ) = ( 78.4

+ 10 . 8 -11 .6

± 3.6 ± 8.9 ) °
+0.040 - 0.038

rB ( DK ) = 0.160

x- - x+ (Dalitz + GLW) = 0.175 ± 0.040
4.4 significance of CPV in B±DK± only, Dalitz+GLW combined
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Semileptonic B-meson decays b c l
Measurement of B DS(*)Kl branching fraction ???
B(BXcl)=(10.99±0.28)%

Reconstructed DS decay modes: (K+K-) ; K*0(K±F) ; KS(+-)K Signal yields are extracted via extended maximum likelihood fit to missing mass distributions
2 M m = ( Eb eam

r - EY ) 2 - | pY |

2

Y = DSK l candidate

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Semileptonic B-meson decays b u l
Study of Bl and B l decays and determination of |Vub|

Physics goals: measure |Vub| and test QCD calculations of form factors Form factor parameterization:

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Study of Bl and B l decays
Study of Bl and B l decays: comparison with theory

Theory model HPQCD (PRD 73, 074502 (2006)) ISGW2 (PRD 52, 2783 (1995)) LCSR (PRD 71, 014015, (2005))

P(2) 13% 0.2% <10-5

Errors are too large to distinguish between B l predictions

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Study of Bl and B l decays
Study of Bl and B l decays: determination of |Vub| from full q2 range

|Vub|=(2.99±0.35)10-3 HPQCD (1 point) |Vub|=(2.92±0.37)10-3 FNAL/MILC (1 point) |Vub|=(2.95±0.31)10 BF )=(1.41±0.05±0.07)10 BF(B0-l+)=(1.75±0.15±0.27)10 (B0-l+
-4 -4 -3

FNAL/MILC (4 points) BF q2 FF 10 )=3% shape)=5% norm.)=8.5% .5%
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Most precise branching fraction measurements

(data (data (data total=

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Measurement of bd, bs, and |Vtd/Vts|
arXiv: 1005.4087

Radiative penguin transitions are flavor changing neutral currents, forbidden at tree level at Standard Model
bd transition is CKM suppressed with respect to bs by a factor 20 in the SM

Motivation
Analysis of equivalent bd and bs decays can be used to measure the |Vtd/Vts| ratio of CKM matrix elements:

BF ( B ) Vtd = Sp * BF ( B K ) Vts
Well measured

2

Isospin factor: 1 for ± ; 0.5 for 0

1- m / M 2 [1 + R ] 1- m / M
2 2 K* 2 B 2 B

3

Form factor ratio

Weak annihilation amplitude corrections

Constraint on |Vtd/Vts| is independent of measured from BS/Bd mixing frequencies: discrepancies between two could indicate new physics Theoretical uncertainty for the |Vtd/Vts| ratio is ~8% for exclusive bs,d decay modes and ~1%(?) for inclusive decays ratio.
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Measurement of bd, bs, and |Vtd/Vts|
Analysis Overview Measure partial branching fractions of sum of seven decay modes in four regions:
BXd and BXs Low hadronic mass (0.5
Extrapolate from partial to inclusive BFs within each mass bin
Need to include unreconstructed decay modes - requires knowledge of fragmentation of hadronic systems Xd and Xs

B B B B B B B

BXd 0 + - + + 0 + + - + 0 + - 0 0 + - + - + + - + 0 + +

BXs B 0 K + - B + K + 0 B + K + - + B 0 K + - 0 B 0 K + - + - B + K + - + 0 B + K +

Combine mass ranges for inclusive BFs in mhad<2.0 GeV/c2 and calculate |Vtd/Vts|
For |Vtd/Vts| - need to extrapolate to all masses. This extrapolation is based on theoretical model of photon spectrum, not on experimental data

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Measurement of bd, bs, and |Vtd/Vts|
Maximum likelihood fit results for BXS (M
ES

and E projections)

Low mass (0.5 - 1.0) GeV/c BK* region

2

High mass (1.0 - 2.0) GeV/c2 non-resonant region

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Measurement of bd, bs, and |Vtd /Vts|
Maximum likelihood fit results for BXd (M
Low mass (0.5 - 1.0) GeV/c2 B(, ) region
ES

and E projections)

High mass (1.0 - 2.0) GeV/c2 non-resonant region

Jagged line artefacts are due to several binned histogram PDFs

First significant observation of b d nonresonant decay modes QFTHEP'2010, Moscow 19


Measurement of bd, bs, and |Vtd /Vts|
Results:
BXs BXs BXd BXd low mass high mass low mass high mass (1.89± (6.57± (1.20± (3.21±

Partial BF
0.08 0.28 0.31 0.81

Inclusive BF
(3.83± (19.2± (1.25± (7.90± 0.16 ±0.15) 10-5 0.8 ±1.7±2.3) 10-5 0.32 ±0.12) 10-6 1.98 ±1.12±1.88) 10

±0.08)10-5 ±0.59)10-5 ±0.11)10-6 ±0.46)10-6

-6

Inclusive branching fractions for mhad<2.0 GeV/c2:
BF(BXs) = (23.0± 0.8 ±1.9 ±2.3)10-5 BF(BXd) = (9.15± 2.01 ±1.24 ±1.88)10
-6

Theoretical formula for |Vtd/Vts| is based on total inclusive BF, so extrapolation of measured inclusive branching fraction to full hadronic mass range is needed. Extrapolation is done according to Kagan-Neubert photon spectrum model [PRD 58, 094012 (1998)]. Additional error (model) ­ from bquark mass uncertainty

BF(BXs) = (38.2± 1.3(stat.) ±3.2(syst.) ±3.8(extrap.) ±1.6(model) )10-5 BF(BXd) = (15.3± 3.4(stat.) ±2.1(syst.) ±3.2(extrap.) ±0.3(model) )10-6 BF(BXd)/ BF(BXs) = 0.040± 0.009(stat.) ±0.005(syst.) ±0.010(extrap.) (model error cancels in BF ratio)
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Measurement of bd, bs, and |Vtd /Vts|
|Vtd/Vts| Extraction:

(b d ) V = 2 td (b s ) Vts

2

(1

+ R

)

The values of and R are calculated using the Wolfenstein and parameters as input. Since the world average of these parameters is based on previous |Vtd/Vts| measurements the and parameters were re-expressed using world average of CKM angle [HFAG, E. Barberio et al. arXiv:0704.3575(hep-ex)]

Full mass region: |Vtd/Vts|=0.199±0.022(stat.)±0.012(syst.)±0.027(extrap.) ±0.002(th.) Cross-check: low mass region only: |Vtd/Vts|=0.197±0.026(stat.)±0.009(syst.)±0.010(th.) agreement with previous measurements: BABAR |Vtd/Vts|=0.233±0.025(exp.)±0.023(th.) [BaBar collab. PRL 98, 151802 (2007)] Belle |Vtd/Vts|=0.195±0.020(exp.)±0.015(th.) [Belle collab. PRL 101, 111801 (2008)]

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Measurement of bd, bs, and |Vtd /Vts|
Conclusions
n n

n

First significant measurement of non-resonant bd decays Measurements of BK*, bs , and B(,) are compatible with previous results Measurement of |Vtd/Vts| is compatible and competitive with previous results with significantly smaller theoretical uncertainty.

This measurement arXiv:1005.4087 (2010)
[1] HFAG winter 2006 results [2] BABAR collab. PRL 98 151802 (2007) [3] Belle collab. PRL 101, 111801 (2008)

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Study of two-photon processes e+e- e+e-P
· Electrons are scattered predominantly
at small angles. · For pseudo scalar meson production the cross section depends on only one form factor F(q12, q22), which describes the P transition.

P

No-tag mode: Ýboth electrons are undetected Ýq12, q22 0 Ý or F(0,0) ÝStudy of resonance parameters

Single-tag mode: Ýone of electrons is detected ÝQ2=-q12 Ý d/dQ2 1/Q6 for light mesons ÝF(Q2,0)

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e+e- e+e-c , c KS K+-, no-tag mode
J.P.Lees et al., PRD 81, 052010 (2010)

c
PDG

C resonance parameters:
Mass, MeV Width, MeV 27.4±2.9 34.3±2.3±0.9 31.7±1.2±0.8

J/

2980.5±1.2 2982.5±1.1±0.9 2982.2±0.4±1.5

BABAR(88 fb-1) BABAR(470 fb-1),

Main sources of systematic uncertainties are unknown background shape and possible interference between the c and non-resonant two-photon amplitudes.

N(c)=13890±320±670

BABAR: (c)B(cKK) = 0.379±0.009±0.031 keV PDG: 0.44±0.04 keV, CLEO: 0.407±0.022±0.028 keV
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e+e- e+e-c(2S), no-tag mode
KSK-+ preliminary

c



c2

c

(2S)

620±70±30 c(2S) events are observed.

J/

Mass, MeV PDG BABAR(88 fb-1) BABAR(521 fb-1), preliminary 3637±4 3630.8±3.4±1.0 3638.3±1.5±0.5

Width, MeV 14±7 17.0±8.3±2.5 14.2±4.4±2.5
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e+e- e+e-c(2S), no-tag mode
c J/
c0



c2

c

(2S)

1190±130±180 c(2S) events are observed.

K+K-+-0 preliminary
B( c K + K - + - 0 ) = 1.44 ± 0.06 ± 0.26, B ( c K S K ± m ) B( c (2 S ) K + K - + - 0 ) = 2.2 ± 0.4 ± 0.5 ±m B ( c ( 2 S ) K S K )
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e+e- e+e- P, single tag

F (Q 2 ) = T ( x, Q 2 ) ( x, Q 2 ) dx
0

1

x is the fraction of the meson
momentum carried by one of the quarks

Hard scattering amplitude for qq transition which is calculable in pQCD

Nonperturbative pion distribution amplitude (DA) describing transition P qq

Data on the form factor are used to test phenomenological models for the meson distribution amplitude.

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e+e- e+e- P, single tag event selection
P Untagged e Along beam axis pt 0 e P
Ýelectron is detected and identified Ýmeson decay products are detected and reconstructed Ýelectron + meson system has low pt Ýmissing mass in an event is close to zero

Tagged e

dN/dQ2

d/dQ2

|F(Q2)|

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e+e- e+e- C form factor
§
J.P.Lees et al., PRD 81, 052010 (2010)

The form factor is normalized to F(0) obtained from no-tag data § The form factor data are fit with the monopole function

LO pQCD

F (Q 2 ) = F (0) (1 + Q 2 / )

§
monopole fit

The result =8.5±0.6±0.7 GeV2 does not contradict to the vector dominance model with =m2J/=9.6 GeV2. § pQCD: Due to relatively large c-quark mass, the c form factor is rather insensitive to the shape of the c distribution amplitude. is expected to be about 10 GeV2 (T. Feldmann, P.Kroll, Phys. Lett. B 413, 410 (1997)). § Lattice QCD: =8.4±0.4 GeV2 (J.J.Dudek, R.G.Edwards, Phys. Rev. Lett. 97, 172001 (2006)).
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and ' form factors
BABAR preliminary BABAR preliminary

Systematic uncertainties independent of Q2 are 2.9% and 3.5% for and ' form factors, respectively CLEO and BABAR data on time-like form factor extracted from e+e- (` ) cross section measurements at Q2=14.2 GeV2 (CLEO) and 112 GeV2 (BABAR) are added

-' mixing in the quark-flavor basis:

= cos n - sin s ;

= sin n + cos s ; where n =

The form factors for |n and |s states are introduced:

1 u u + dd ; s = ss 2

(

)

F = cos Fn - sin Fs , F = sin Fn + cos Fs
Q 2 Fs (Q 2 ) = 2 52 f s , Q 2 Fn (Q 2 ) = f 3 3
n

41°

with asymptotic limits

where decay constants are expected to be fn=f, fs=1.34f , and DA for the |n state is close to the 0 DA with the only difference: a factor of 3/5 coming from quark charges

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Form factors for |n and |s states
· The Q2 dependencies of the measured |n
and 0 form factors are strongly different. · The data on the |n form factor are described well by the model with BMS DA.
A.P.Bakulev, S.V.Mikhailov, N.G.Stefanis, Phys. Rev. D 67, 074012 light-cone sum rule method at NLO pQCD+twist-4 power corrections.

· For |s all data points lie well below the pQCD
prediction for the asymptotic DA. · The result for |s strongly depends on mixing parameters, for example, on a possible two-gluon contents in / .
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Summary
v High accuracy measurement of CKM angle by Dalitz-plot analysis

v

v v

v

with low model uncertainty. Compelling evidence of direct CP violation in B± D(*)K(*)± decays Most presize measurements of the B0-l+ and B0-l+ branching fractions, tests of q2 spectrum agreement with theoretical predictions, and new determination of |Vub| Study of BXd and BXs decays, new measurement of |Vtd/Vts|, first significant measurement of BXd nonresonant decays New precise measurements of the c and c(2S) masses and widths, first observation of the decay modes c K+K-+-0 and c(2S) K+K-+-0. * c, , / transition form factors are measured in the range from 2 to 50 GeV2 (c) and from 4 to 40 GeV2 (, /). The c form factor data are in good agreement with QCD and VDM predicitions. The Q2 dependencies of and / transition form factors strongly differ from that of * 0 transition form factor.

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