Table Of Content2 Updated measurements of hadronic B decays at
1
0 CDF
2
n
a
J
5
2
]
x MichaelJ. Morello∗†
e ScuolaNormaleSuperiorediPisaandINFNSezionediPisa
-
p E-mail: [email protected]
e
h
[
The CDF experimentat the Tevatron pp¯ collider established that extensive and detailed explo-
1 ration of the b–quark dynamics is possible in hadron collisions, with results competitive and
v
supplementary to those from e+e colliders. This provides a rich, and highly rewarding pro-
7 −
6 gram that has currently reached full maturity. In the following I report some recent results on
2
hadronicdecays: the evidenceforthe charmlessannihilationdecaymodeB0 p +p , andthe
5 s → −
. first reconstruction in hadron collisions of the suppressed decays B D( K+p )K and
1 − − −
→ →
0 B D( K+p )p .
− − −
2 → →
1
:
v
i
X
r
a
The2011EurophysicsConferenceonHighEnergyPhysics,EPS-HEP2011,
July21-27,2011
Grenoble,Rhône-Alpes,France
Speaker.
∗
†OnbehalfoftheCDFCollaboration.
(cid:13)c Copyrightownedbytheauthor(s)underthetermsoftheCreativeCommonsAttribution-NonCommercial-ShareAlikeLicence. http://pos.sissa.it/
UpdatedmeasurementsofhadronicBdecaysatCDF MichaelJ.Morello
1. Evidence forthe charmless annihilationdecay modeB0 p +p
s −
→
Two-body non-leptonic charmless decays of b–hadrons are very widely studied processes in
flavor physics. The variety of open channels involving similar final states provides useful exper-
imental information to improve the accuracy of effective models of strong interaction dynamics.
Somedecaysreceivecontributionsfromhigher-order(‘penguin’)transitions,andarethereforesen-
sitivetothepossible presenceofnewphysicsininternal loops.
TheB0 p +p andB0 K+K decaymodeshaveaspecial status, inthatallquarks inthe
s − −
→ →
final state are different from those in the initial state. This limits the possible diagrams that can
contribute tothesedecaytopenguin-annihilation (PA)andW-exchange (E)topologies. Theyhave
never been observed, andthebest upper limits comefrom [1,2]. Theseamplitudes are difficultto
predictwithinthecurrentphenomenological models,andareoftenneglectedincalculations ofde-
cayswheretheyarenottheonlycontributors,usinggenericargumentofsmallness. Thesediagrams
may carry different CP-violating and CP-conserving phases with respect to leading diagrams; the
lack of knowledge of their size therefore introduces unavoidable uncertainties in the conclusions
drawnfromtheanalyses ofotherwell-studied decays, likeB0 p +p andB0 K+K . Amea-
− s −
→ →
surementofbranchingfractionofbothB0 p +p andB0 K+K wouldbeparticularlyuseful,
s − −
→ →
asitallowabetterdetermination ofthestrength ofPAandEamplitudes.
CDF Run II Preliminary (cid:242) L dt = 6.11 fb-1 CDF Run II Preliminary (cid:242) L dt = 6.11 fb-1
22MeV/MeV/cc11550000 dtoattaal 22MeV/MeV/cc 110044 dtoattaal BB00sfifi KK++pK-- LB0s0bfifi Kp+-pK+-
0 0 B0fi K+p - 0 0 B0fi p +p - L 0bfi p+p -
per 1per 1 BB0s0fifi pK++pK-- per 1per 1 110033 B0fi K+K- B0sfi p +p -
ndidates ndidates 11000000 LLB0s0b0bfififi Kpp++-pKp+-- ndidates ndidates 110022 MCoumltibboindayt oBri adle bckagys
CaCa B0fi K+K- CaCa
550000 B0sfi p +p - 1100
Multibody B decays
Combinatorial bkg
11
55..00 55..22 55..44 55..66 55..88 55..00 55..22 55..44 55..66 55..88
IInnvvaarriiaannpptt pp --mmaassss [[GGeeVV//cc22]] IInnvvaarriiaannpptt pp --mmaassss [[GGeeVV//cc22]]
Figure1: InvariantmassdistributionofreconstructedB0 h+h candidates(linearscaleontheleftand
(s)→ ′−
logarithmic scale on the right). The charged pion mass is assigned to both tracks. The sum of the fitted
distributionsandtheindividualcomponentsofsignalandbackgroundareoverlaidonthedatadistribution.
CDFrecentlysearchedforbothB0 p +p andB0 K+K ,usingadatasampleof6fb 1of
s − − −
→ →
integratedluminosity. Anextendedunbinnedlikelihoodfit,incorporatingkinematic(invariantmass
and momenta) and particle identification (dE/dx) information, is used to determine the fraction of
eachindividualB0 h+h (wherehisforapionorkaon)modeinthesample. Thefitprojection
(s)→ ′−
on the invariant pp -mass is reported in fig. 1. A 3.7s significant signal is observed for the B0
s
→
p +p mode, whilea deviation atthe 2s level from nosignal hypothesis isreported for the B0
−
→
K+K . The measured branching ratios are B(B0 p +p )=(0.57 0.15 0.10) 10 6 and
− s − −
→ ± ± ×
2
UpdatedmeasurementsofhadronicBdecaysatCDF MichaelJ.Morello
B(B0 K+K )=(0.23 0.10 0.10) 10 6 [3]. A90%confidenceintervalfortheB0 K+K
− − −
→ ± ± × →
mode is also reported [0.05,0.46] 10 6 [3]. The result for the B0 p +p mode is consistent
− s −
× →
with the previous upper limit (< 1.2 10 6 at 90% C.L.), based on a subsample of the current
−
×
data [2] and it is in agreement with the very recent result from LHCb [4]. This agrees with the
predictionsinRef.[5]withinthepQCDapproach. Itishigherthanmostotherpredictions[6,7,8].
Thepresent measurementofB(B0 K+K )supersedes theprevious limit[2]. Thecentral value
−
→
isinagreement withotherexistingmeasurements [9,1,4],andwiththeoretical predictions [6,8].
2. g from B DK decays
→
Conventionally, CPviolating observables are written interms of theangles a , b and g ofthe
“Unitarity Triangle", obtained from one of theunitarity conditions ofthe CKMmatrix. While the
resolution on a and b reached a good level of precision, the measurement of g is still limited by
the smallness of the branching ratios involved in the processes. Among the various methods for
the g measurement, those which make use of the tree-level B D0K decays have the smallest
− −
→
theoretical uncertainties. Infactg appears astherelative weakphase between twoamplitudes, the
favored b cu¯stransition oftheB D0K ,whoseamplitude isproportional toV V ,andthe
− − cb us
→ → 0
color-suppressed b uc¯stransitionoftheB D K ,whoseamplitudeisproportionaltoV V .
− − ub cs
The interference be→tween D0 and D0, decayin→g into the same final state, leads to measurable CP-
violating effects, from which g can be extracted. The effects can be also enhanced choosing the
interfering amplitudes of the same order of magnitude. All methods require no tagging or time-
dependent measurements, andmanyofthemonlyinvolve charged particlesinthefinalstate.
CDF Run II Preliminary L = 7 fb-1 CDF Run II Preliminary L = 7 fb-1
int int
40 40
2c B- fi D0 p - fi [K+ p -] p - 2c B+ fi D0 p + fi [K- p +] p +
V/ sup V/ sup
e Data e Data
M M
er 14 30 BTBo-- fifital DD0s0suupp pK-- er 14 30 TBBo++ tfifial DD0s0suupp pK++
p B- fi K-p +p - p B+ fi K+p -p +
ents 20 BB-- fifi DD00Kp --,, DD00fifi XX ents 20 BB++ fifi DD00Kp ++,, DD00fifi XX
Ev B0 fi D0*- e+ n e Ev B0 fi D0*+ e- n e
B- fi D0* p - B+ fi D0* p +
Combinatorial background Combinatorial background
10 10
0 0
5.2 5.3 5.4 5.5 5.6 5.2 5.3 5.4 5.5 5.6
K+p -p - mass [GeV/c2] K-p +p + mass [GeV/c2]
Figure2:InvariantmassdistributionsofB Dh forthesuppressedmode(bottommesonontheleftand
± ±
→
antibottomontheright). ThepionmassisassignedtothechargedtrackfromtheBcandidatedecayvertex.
Theprojectionsofthelikelihoodfitareoverlaid.
In a data sample of about 7 fb 1 CDF reports the first reconstruction in hadron collisions
−
of the suppressed decays B D( K+p )K and B D( K+p )p , which are the main
− − − − − −
→ → → →
ingredient of the the ADS method [10]. Also in this case an extended unbinned likelihood fit,
3
UpdatedmeasurementsofhadronicBdecaysatCDF MichaelJ.Morello
incorporating kinematic (invariant mass) and particle identification (dE/dx) information, is used
to determine the fraction of each individual modes. The fit projection on the invariant Kpp -mass
is reported in fig. 2. CDF measures the following asymmetries: A (K)= 0.82 0.44(stat)
ADS
− ± ±
0.09(syst) andA (p )=0.13 0.25(stat) 0.02(syst) [11],andfortheratiosofdoublyCabibbo
ADS
± ±
suppressed mode to flavor eigenstate CDF finds R (K)=[22.0 8.6(stat) 2.6(syst)] 10 3
ADS −
± ± ×
andR (p )=[2.8 0.7(stat) 0.4(syst)] 10 3 [11]. Theresultsareinagreementwithexisting
ADS −
± ± ×
measurements performed at¡ (4S)resonance [12]andveryrecentlyatLHCb[13].
3. Conclusions
CDFexperiment attheTevatronkeepsproviding excellentresultsintheexploration ofHeavy
Flavor Physics, owing to CP-symmetric initial states in √s=1.96 TeV pp¯ collisions, large event
samples collected by well-understood detector, and mature analysis techniques. In summary, this
shortwrite-upreportsonthefirstevidenceforthecharmlessannihilationdecaymodeB0 p +p ,
s −
→
an updated upper limit for the B0 K+K mode, and on the first reconstruction in hadron colli-
−
→
sionsofthesuppressed decaysB D( K+p )K andB D( K+p )p .
− − − − − −
→ → → →
References
[1] K.Abeetal.(BelleCollaboration),ObservationofBDecaystoTwoKaons,Phys.Rev.Lett.98,
181804(2007)[hep-ex/0608049].
[2] T.Aaltonenetal.(CDFCollaboration),ObservationofNewCharmlessDecaysofBottomHadron,
Phys.Rev.Lett.103,031801(2009)[hep-ex/0812.4271].
[3] T.Aaltonenetal.(CDFCollaboration),Evidenceforthecharmlessannihilationdecaymode
B0 p +p ,hep-ex/1111.0485,submittedtoPhys.Rev.Lett.
s → −
[4] LHCbCollaboration,Charmlesschargedtwo-bodydecaysatLHCbwith2011data,
LHCb-CONF-2011-042;A.Carbone,theseproceedings.
[5] A.Alietal.,CharmlessnonleptonicB decaystoPP,PV,andVVfinalstatesintheperturbativeQCD
s
approach,Phys.Rev.D76,074018(2007)[hep-ph/0703162];Y.Lietal.,Branchingratioand
CPasymmetryofB0 p +p decaysintheperturbativeQCDapproach,Phys.Rev.D70,034009
s → −
(2004)[hep-ph/0404028].
[6] M.BenekeandM.Neubert,QCDfactorizationforB PPandB PV decays,Nucl.Phys.B675,
→ →
333(2003)[hep-ph/0308039].
[7] J.-F.Sun,G.-H.Zhu,andD.-S.Du,PhenomenologicalAnalysisofCharmlessDecaysB PP,PV
s
→
withQCDFactorization,Phys.Rev.D68,054003(2003)[hep-ph/0211154].
[8] H.-Y.ChengandC.-K.Chua,QCDFactorizationforCharmlessHadronicB DecaysRevisited,Phys.
s
Rev.D80,114026(2009)[hep-ph/0910.5237];RevisitingcharmlesshadronicB decaysin
u,d
QCDfactorization,Phys.Rev.D80,114008(2009)[hep-ph/0909.5229].
[9] B.Aubertetal.(BABARCollaboration),ImprovedMeasurementsoftheBranchingFractionsfor
B0 p +p andB0 K+p ,andaSearchfroB0 K+K ,Phys.Rev.D75,012008(2007)
− − −
→ → →
[hep-ex/0608003].
[10] D.Atwood,I.DunietzandA.Soni, EnhancedCPViolationwithB KD0(D¯0)Modesand
→
ExtractionoftheCabibbo-Kobayashi-MaskawaAngleg ,Phys.Rev.Lett.78,3257(1997).
4
UpdatedmeasurementsofhadronicBdecaysatCDF MichaelJ.Morello
[11] T.Aaltonenetal.(CDFCollaboration),Measurementsofbranchingfractionratiosand
CP-asymmetriesinsuppressedB D( K+p )K andB D( K+p )p decays,Phys.Rev.
− − − − − −
→ → → →
D84,091504(2011)[hep-ex/1108.5765].
[12] Y.Horiietal.(BelleCollaboration),EvidencefortheSuppressedDecayB DK ,D K+p ,
− − −
→ →
Phys.Rev.Lett.106,231803,(2011)[hep-ex/1103.5951];P.delAmoSanchezetal.(BABAR
Collaboration),Searchforb utransitionsinB DK andB D K Decays,Phys.Rev.D
− − − ∗ −
→ → →
82,072006,(2010)[hep-ex/1006.4241].
[13] LHCbCollaboration,EvidenceforthesuppresseddecayB (K p ) K ,
± ∓ ± D ±
→
LHCb-CONF-2011-044;G.Wilkinson,theseproceedings.
5
