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The anatomy of quark flavour observables in the flavour precision era. Fulvia De Fazio INFN- Bari. Portoroz 2013. Two topics Improving data precision and reducing theoretical uncertainties (FPE) would it be possible to understand from flavour observables

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slide1

The anatomy of quark flavour observables

in the flavour precision era

Fulvia De Fazio

INFN- Bari

Portoroz 2013

  • Twotopics
  • Improving data precision and reducingtheoreticaluncertainties (FPE)
  • woulditbepossibletounderstandfromflavourobservables
  • if the lightest NP messangeris a new Z’ gaugeboson?
  • anexistingtension: exclusivesemileptonic b  c decays:
  • anomalousenhancementofmodeswith a t in the final state

Based on works in collaborationwith

A.J.Buras, J. Girrbach (Munich)

&

P. Biancofiore, P. Colangelo (Bari)

slide2

Anatomy of Z’ with FCNC in the FPE

A.J.Buras, J. Girrbach, FDF

JHEP 1302 (2013) 116

  • CKM parametershavebeendeterminedbymeansoftree-leveldecays
  • Non-perturbativeparameters are affectedbyverysmalluncertainties and fixed
  • Letusconsider the following case
  • Thereexists a newneutralgaugeboson Z’ mediatingtree-level FCNC processes
  • MZ’=1 TeVfordefiniteness
  • Couplingstoquarks are arbitrarywhilethosetoleptons are assumedalready
  • determinedbypurelyleptonicmodes

Existing data constrain Z’ couplingstoquarks

Fourpossiblescenariosforsuchcouplings can beconsidered

Predictions on correlationsamongflavourobservablesprovide the path

toidentifywhich, in any, ofthemisrealized in nature

slide3

Anatomy of Z’ with FCNC in the FPE

Analogousscenarios can beconsideredfor the quark pairs (bs) and (sd)

Two cases

|Vub| fixedto the exclusive (smaller) value

|Vub| fixedto the inclusive (larger) value

slide4

Anatomy of Z’ with FCNC in the FPE: the Bs system

Weconsider the fourobservables:

Mass difference

in the B̅s–Bs system

CP asymmetry in

BsJ/ f

CP asymmetry in

Bsm+m-

Theydependall on

Imposing the experimentalconstraints:

wefindallowedrangesfor the parameters

s23 >0 & 0<d23<2p

slide5

Bs system in LHS1 scenario

A3

A4

Blueregions come from the constraint on Sf

Red onesfrom the constraint on DMs

Fourallowedoases:

twobigones & twosmallones

A2

A1

A1

Big

Small

Big

Small

Howtofind the optimaloasis?

slide6

The decay Bsm+m-

SMeffectivehamiltonian one master function Y0(xt)

independent on the decayingmeson

and on the leptonflavour

Z’contributionmodifiesthisfunctionto:

a newphase

The variousscenariospredictdifferentresults

Theoretically

cleanobservable:

phaseof the function S

entering in the box diagram

vanishes in SM

the newphaseinvolved

LHCb 1211.2674

SM

slide7

The decay Bsm+m-

A1

smalloases

A3

exp 1 srange

Excludes the smalloases

Sm+m- >0 wouldchoose A1

Sm+m- <0 wouldchoose A3

No differencesfound in LHS2

slide8

Anatomy of Z’ with FCNC in the FPE: the Bd system

Weconsider the fourobservables:

Mass difference

in the B̅d–Bd system

CP asymmetry in

BdJ/ Ks

CP asymmetry in

Bdm+m-

Theydependall on

Imposing the experimentalconstraints:

wefindallowedrangesfor the parameters

s13 >0 & 0<d13<2p

slide9

Bd system in LHS1 & LHS2 scenarios

B3

B4

Blueregions SKs

Red ones DMd

B1

B2

slide10

Bd system in LHS1 & LHS2 scenarios

B2

B2

B4

B3

B4

B1

B3

B1

LHCb 1203.4493

SM

  • in the smalloases B(Bdm+m- ) is always larger than in SM
  • the signof Sm+m- distinguishes B1 from B3 and B2 from B4

Correlationbetween Sm+m- andB(Bdm+m- ): LHS1 vs LHS2

LHS1 : in B1 Sm+m- >0 & B(Bdm+m- ) > B(Bdm+m- ) SM

in B3 Sm+m- <0 & B(Bdm+m- ) < B(Bdm+m- ) SM

LHS2 : in B1 Sm+m- >0 & B(Bdm+m- ) < B(Bdm+m- ) SM

in B3 Sm+m- <0 & B(Bdm+m- ) > B(Bdm+m- ) SM

slide11

RHS1 & RHS2 scenarios

Means Z’ withexclusively RH couplingstoquarks

QCD isparityconserving hadronicmatrixelementsofoperatorswith RH currents

& QCD correctionsremainunchanged

DF=2 constraintsappear the sameas in LHS scenarios  the oasesremain the same

DF=1 observables: decaystomuonsgovernedby the function Y

Thereis a changeofsignof NP contributions in a givenoasis

slide12

RHS1 & RHS2 scenarios

Bs system

LHS

RHS

Sm+m- >0 wouldchoose A1

Sm+m- <0 wouldchoose A3

Sm+m- >0 wouldchoose A3

Sm+m- <0 wouldchoose A1

Bd system

Correlationbetween Sm+m- andB(Bdm+m- ): LHS1 vs LHS2

LHS1 : in B1 Sm+m- >0 & B(Bdm+m- ) > B(Bdm+m- ) SM

in B3 Sm+m- <0 & B(Bdm+m- ) < B(Bdm+m- ) SM

LHS2 : in B1 Sm+m- >0 & B(Bdm+m- ) < B(Bdm+m- ) SM

in B3 Sm+m- <0 & B(Bdm+m- ) > B(Bdm+m- ) SM

Oppositesigns

in RHS scenarios

On the basisoftheseobservablesitwouldnotbepossibletoknowwhether

LHS in oases A1 (B1) isrealized or RHS in oases A3 (B3)

slide13

LRS1 & LRS2 scenarios

Bs system

Bd system

Maindifferencewithrespectto the previouscases:

No NP contributiontoBd,sm+m-

 We cannot rely on this observable to identify the right oases

ALRS1 & ALRS2 scenarios

Similarto LHS scenario, but NP effectsmuchsmaller

slide14

Can we exploit other observables?

b  s l+l-

SM NP

operators

coefficients

slide15

b  s l+l-

W. Altmannshofer & D. Straub,

JHEP 1208 (2012) 121

Exploitingpresent data constraints can beobtained:

A3

A1

A1

Oasis A1 excluded in LRS

slide16

b  s l+l-

Blackregions are excluded

due to the constraint on C10’

An enhancementof B(Bsm+m- ) withrespectto SM isexcluded

ONLY in RHS!!

Possibilitytodifferentiatebetween LHS and RHS scenarios,

butonlyif B(Bsm+m- )> B(Bsm+m- )SM

slide17

b  s n̅n

SM

EXP

Altmannshoferet al.

JHEP 04 (2009) 022

Sensitive observables

excludedby b  s l+l-

Cleardistinctionbetween LHS and RHS

slide18

B  D(*) t n̅t

BaBarmeasurements:

BaBar, PRL 109 (2012) 101802

SM

  • BaBarquotes a 3.4 sdeviationfrom SM predictions
  • isthisrelatedto the enhancementof B(B tnt) ?

…but…

SM predictionfor

|Vub|=0.0035  0.0005

slide19

B  D(*) t n̅t

  • Mostnaturalexplanation: newscalarswithcouplingstoleptonsproportionaltotheir mass
  • wouldexplain the enhancementoftmodes
  • wouldenhancebothsemileptonic and purelyleptonicmodes

The simplestofsuchmodels (2HDM) hasbeenexcludedbyBaBar:

No possibilitytosimultaneouslyreproduce R(D) and R(D*)

  • Alternative explanationsusingseveralvariantsofeffectivehamiltonian
  • S. Fajferet al, PRD 85 (2012) 094025; PRL 109 (2012) 161801
  • A. Crivellinet al., PRD 86 (2012) 054014
  • A. Dattaet al., PRD 86 (2012) 034027
  • A. Celiset al., JHEP 1301 (2013) 054
  • D. Choudhuryet al, PRD 86 (2012) 114037
slide20

B  D(*) t n̅t

P. Biancofiore, P. Colangelo, FDF

1302.1042, PRD 87 (2013) 074010

  • A differentstrategy:
  • consider a NP scenario thatenhancessemileptonicmodesbutnotleptonicones
  • predictsimilareffects in otheranalogousmodes

SM NP

newcomplexcoupling: eTm,e=0, eTt≠ 0

Charmedmeson

 |eT|2

 Re(eT)

  • A simlarstrategy in
  • M. Tanaka & R. Watanabe 1212.1878
slide21

B  D(*) t n̅t

Including a newtensoroperator in Heff :

isitpossibletoreproduceboth R(D) and R(D*)?

Big circle: R(D) constraint

overlapregion:

Smallcircle: R(D*) constraint

varyingeT in thisrangepredictions

forseveralobservables can begained

slide22

B  D(*) t n̅t: whichobservables are the most sensitive ?

Comparisonwith the latestBaBarresults:

BaBarCollab. 1303.0571

include NP

The spectradG/dq2cannotdistinguish the SM from the NP case

slide23

B  D*t n̅t

Forward-Backwardasymmetry

angle between the chargedlepton and

the D* in the leptonpairrest-frame

The SM predicts a zero at q2 6.15 GeV2

In NP the zero isshiftedto q2 [8.1,9.3] GeV2

  • Uncertainty in the SM predictionis due to 1/mQcorrections
  • and to the parametersof the IW functionfittedby Belle
  • NP includesuncertainty on eT
slide24

B  D** t n̅t

D**=positive parityexcitedcharmedmesons

Twodoublets:

(D(s)0*,D(s)1’) withJP=(0+,1+) and (D(s)1,D(s)2*) withJP=(1+,2+)

Formfactorsforsemileptonic B decaystothesestates can beexpressed in termsof

universalfunctionsanalogousto the IW

B  (D(s)0*,D(s)1’)

t1/2(w)

B  (D(s)1,D(s)2*)

t3/2(w)

Weconsideragainratios in which the dependence

on the modelfor the tfunctionsmostlydrops out

slide25

B  D** t n̅t

Orange= non strange

Bluecircle= SM

Green=strange

Triangle= SM

The inclusionof the tensoroperatorproduces a sizableincrease in the ratios

Forward-backwardasymmetries

shift in the position of the zero

the zero disappears

slide26

summary

Studyingcorrelationsbetweenflavourobservablesmayleadusto

select the right scenario (ifany) for Z’ couplingstoquarksfor MZ’=1 TeV

Largermasses (>5 TeV) havenegligible impact on the observablesconsidered

  • The mostconstrained system isthatofBs
  • importantroleisplayedby Sf and B(Bsm+m-)
  • highest sensitivity to RHC is that of b  s l+l- and b  s n̅n

Anomalousenhancementof R(D(*)) couldbeexplainedintroducing a newtensoroperator

in the effectivehamiltonian.

Differentialdistributions help to discriminate this scenario from SM

Largeeffectsforseen in B  D** t n̅t