bsg Exclusive Decays

Akimasa Ishikawa(Tohoku University)

Evidence for bsg

• CLEO found an evidence for bsg process using exclusive BK*(892)g decays in 1993 with only 1.38fb-1 data on Y(4S).

More than 20 years has passed from the evidence and now….

Now we are here

• Now we (Babar and Belle) have more than 800 times larger data of 1144fb-1 (433fb-1+711fb-1) on Y(4S) than data with which CLEO found an evidence for bsg.

• Further, LHCb collected 3fb-1 at 7TeV and 8TeV at pp collisions.– sbb = 7.7mb for pT

bb > 5GeV and 2.5 < h < 4.0 at 7TeV

Copious numbers of B hadrons are available.

Ideal tool to search for new physics• Exclusive bsg decays can be used to measure

– Branching fraction (BF)• Fragmentation of Xs

– Direct CP Violation (ACP)• To Search for New phase

– Time dependent CP Violation (SCP)• For B0fCPg modes• to search for right handed current/new phase• CPV is suppressed by O(ms/mb)

– Isospin Violation (D0+ or AI)• Spectator dependent operator

– Up-Down Asymmetry (AUD)• For BK1gKppg• To search for right handed current• New physics makes |AUD| value smaller than the SM

– Photon Polarization from conversion (no groups measure yet)• To search for right handed current

Observed Exclusive Decays• Now we observed

– BK*(892)g in 1993– BK2*(1430)g in 2000– BKfg in 2004– BKhg in 2005– BK1(1270)g in 2005– BpLg in 2007– BKh’g in 2010

12.6

12.33.62.40.80.80.7

9.557.3

Exclusive Fraction [%]K*(892)K1(1270)K2*(1430)KηKη'KΦpΛnon-res Kππothers

Only 40% are exclusively known!

Direct CPV• In the SM, bsg process is dominated by single

EW penguin diagram, and further weak phase in Vts is suppressed by O(l2), so direct CPV in bsg is small. – E.g. ACP(BK*(892)g) = -0.6±0.4%

• If new physics contribution to bsg has sizable amplitude and weak (+strong) phase, direct CPV could appear.

• Is the difference of direct CPV btw B0 and B+ interesting/sensitive NP also for exclusive decays?– Benzke, Lee, Neuber and Paz propose it for inclusive

decays as a sensitive probe for new physics.

Matsumori, Sanda, Keum

Direct CPV in BK*(892)g

ACP B0 B+ B

Babar 347fb-1 -1.6±2.2±0.7 % 1.8±2.8±0.7 % -0.3±1.7±0.7 %

Belle 78fb-1 n.a. n.a. -1.5±4.5±1.2 %

LHCb 1fb-1 0.8±1.7±0.9 % n.a. 0.8±1.7±0.9 %

Average 0.7±1.9 % 1.8±2.9 % 0.1±1.3 %

• LHCb reported ACP with 1fb-1

– Only with K*0K+p-

• W.A. consistent with null asymmetry predicted in the SM– -0.6±0.4 %

• exp error 3times larger than theo– LHCb 1fb-1 3fb-1

– Belle 78fb-1 711fb-1

Matsumori, Sanda, Keum

Isospin Violation

• Isospin Violation can be calculated in the SM.

– +5.0 ~ +10 %– +2.7±0.8 %

• If new physics has isospin breaking contributions, such as spectator dependent diagrams, D0- could be deviated from the SM value– Even sign of Isospin Violation flips

Matsumori, Sanda, Keum

Kagan, Neubert

Isospin Violation in BK*(892)g

• Babar and Belle measured isospin violation– thanks to high reconstruction

efficiency for Ks and p0 involved modes at e+e- machine

• Consistent with SM Predictions– +5.0 ~ +10 %– +2.7±0.8 %

D0-

Babar 347fb-1 6.6±2.1±2.2 %

Belle 78fb-1 1.2±4.4±2.6 %

Average 5.2±2.6 %

Matsumori, Sanda, Keum

Kagan, Neubert

Time dependent CPV• In the SM, photon emitted from b is predominantly left handed. Time

dependent CPV in BfCPg is small due to small interference

• If new physics has right handed current, time dependent CPV emerges by interference.

• Gluon emission bsgg processes make SSM larger than naive calculation??

Grinstein, Pirjol

Ball, Zwicky

Atwood, Gronau, Soni

Atwood, Gershon, Hazumi, Soni

SSM ~ O(0.1) Grinstein, Grossman, Ligeti, Pirjol

Matsumori, Sanda

Time Dependent CPV in BKhg

• Recently Belle reported measurement of time dependent CPV in BKhg with full data

• Measured values are out of physical boundary but consistent with null CPV.

Preliminary711fb-1

SM prediction

Summary of time dependent CP Violation

• Four decay modes are used to search for time dependent CPV.– fCP = Ksp0(K*0), Ksh, Ksr, Ksf

• All are consistent with null with stat errors.

fCP Babar Belle

Ksp0 (K*0) 427fb-1 495 fb-1

Ksh 427fb-1 711 fb-1

Ksr n.a. 605 fb-1

Ksf n.a. 711 fb-1

Up Down Asymmetry• Polarization of photon can be extracted from

the BK1g(Kpp)g process by measuring up down asymmetry (photon polarization from K1 polarization).– Angle q btw photon and normal vector to K1

decay plane.

– Interference btw rK and K*p generates imaginary part.• modes involving p0 gives larger AUD

• Need theoretical calculation of the amplitudes

Gronau, Grossman, Pirjol, Ryd

Up Down Asymmetry in BKppg• LHCb observed AUD with 3fb-1 in BK+p-p+g

– With 13876±153 signal events

• Measure AUD with 4 bins of MKpp

– No resonance separation• 5.2s significance from null polarization

• No interpretation to photon polarization yet

bdg Exclusive Decays

Given title is bsg exclusive decays but I would add bdg

bdg Decays

• The bdg is suppressed by Vtd– About 30 times smaller than bsg ( |Vtd/Vts|2 ) – Need very good PID detector and EM Calorimeter

• The observables to search for NP are the same as the bsg but NP contribution could be different.– Branching fraction (BF)– Direct CP Violation (ACP)

– Time dependent CP Violation (SCP)

– Isospin Violation (Dr)

– Up-Down Asymmetry (AUD)– Photon Polarization from conversion (no groups measure yet)

Observation of bdg

• Belle had observed bdg process using exclusive B(r, w)g with 357fb-1 data in 2006

|Vtd/Vts|, ACP and Dr• |Vtd/Vts| can be measured from the

ratio of BF of B (r,w)g and BK*g– Consistent with the SM

• Direct CPV in Br+ g consistent with null • Dr Isospin Violation large?

– 2~3s deviation

– + 4 +14 -7 %

– - 10±6 %– - 5.4±3.9 % if f3 = 60deg– - 4.6±7 %

|Vtd/Vts| ACP(B+r+g) Dr

Babar 423fb-1 n.a.

Belle 605fb-1

Average n.a.

Lyon, Zwicky

Ball, Jones, Zwicky

Beneke, Feldmann, Seidel

Ali, Lunghi

Time Dependent CPV in B0r0g

• Only Belle had measured time dependent CPV in B0r0g• 48±14 signal events are used for fits.

– Though signal yield is smaller than B0Ksp0g, fraction of events used for time dependent fit is larger thanks to easier vertex reconstruction with r0p+p-

• The results are consistent with null asymmetry

Summary

• Many studies of bsg are performed in more than 20 years to search for new physics.– No hint of new physics yet.

• New window bdg was opened since 2006.– A hint in Isospin Asymmetry??

• Some analyses in bsg and all analyses in bdg are still statistical error dominant– Need higher luminosity experiments– Belle II and LHCb upgrade

• Some theoretical predictions are different btw groups.– Isospin violation– Time dependent CPV– Hope the predictions improved in coming several years.

backup

CCP = - ACP