Charmless b-hadron decays - Agenda (Indico) · 2017-03-10 · Charmless Decays Can proceed via tree...

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Charmless b-hadron decays Giulio Dujany on behalf of the LHCb collaboration XXXI e Rencontres de Physique de la Vall ´ ee d’Aoste

Transcript of Charmless b-hadron decays - Agenda (Indico) · 2017-03-10 · Charmless Decays Can proceed via tree...

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Charmless b-hadron decays

Giulio Dujany

on behalf of the LHCb collaboration

XXXIe Rencontres de

Physique de la Vallee d’Aoste

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Overview

1 Introduction

2 Baryonic B decaysObservation of the B0

s → pΛK− decay [LHCb-CONF-2016-016]Observation of the B0

(s)→ pph+h′− decays

3 CP violation in b decaysTime dependent CP violation in the B0 → π+π− and B0

s → K+K−

decays [LHCb-CONF-2016-018]Evidence for CP violation inΛ0

b → pπ−π+π− [Nat. Phys. (2017)]

4 Rare B decaysSearch for the B0

s → η′φ decay [arXiv:1612.08110, Submitted to JHEP]Observation of the B0→ K+K− decay [Phys. Rev. Lett. 118 (2017)081801]

5 Conclusions

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Charmless Decays

Can proceed viatree b→ u

penguin b→ s, b→ dTree, suppressed by Vub, canhave similar magnitude topenguinsSensitivity to weak phases fromtree-penguin interferenceNew physics can appear in loopsProvide inputs and tests forQCD models

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Baryonic B decays

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MotivationsMany baryonic B decays still to be studied / observedMulti-body final state tend to have larger BF that 2-body ones

B(B0 → Λ−c pπ+π−) ∼ 10−3 � B(B0 → Λ−

c pπ0) ∼ 10−4

� B(B0 → Λ−c p) ∼ 10−5

B(B0 → ppK0) ∼ 10−6 � B(B0 → pp) ∼ 10−8

Threshold enhancement in baryon-antibaryon systems observed inmany decay modes (see eg. [Eur. Phys. J. C74 (2014) 3026])

Threshold enhancement observed forthe first time by Belle in B± → ppK±

[Phys. Rev. Lett. 88 (2002) 181803]0

20

40

60

80

100

120

2 2.5 3 3.5 4 4.5Mpp

_ (GeV/c2)

dN /

dMpp_

(Eve

nts

/ (G

eV/c

2 ))

Even

ts /

(5 M

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2 )

0

5

10

3 3.05 3.1 3.15

FIG. 2. The fitted yield divided by the bin size forB+ → ppK+ as a function of pp mass. The charm veto isapplied. The distribution from non-resonant B+ → ppK+

MC simulation is superimposed. The inset shows the pp massdistribution for the J/ψK+ signal region.

the ECL shower width distribution is consistent with MCexpectations for the proton and anti-proton candidates.In addition, we check the branching fraction as the cutson the proton and anti-proton probabilities and likeli-hood ratio are varied. We do not observe any systematictrends beyond statistics.

To verify the analysis procedure and branching frac-tion determination, we remove the J/ψ veto and ex-amine the decay chain B+ → J/ψK+, J/ψ → pp. Aclear signal of 26.4 ± 5.2 events is then observed in the∆E spectrum. We also observe 25.9 ± 5.1 events inthe Mbc distribution. The pp invariant mass spectrumfor J/ψK+ signal candidates is shown as an inset inFig. 2. We use the ∆E yield and the MC detectionefficiency of 0.30 to determine the branching fractionB(B+ → J/ψK+) = (13.1 ± 2.6) × 10−4. This is ingood agreement with the PDG world average, B(B+ →J/ψK+) = (10.0±1.0)×10−4 [12], which was obtained byexperiments that reconstruct the J/ψ in dilepton modes.

We also examined two related decay modes B0 →ppKS and B+ → ppπ+ that may help clarify the inter-pretation of the signal. Measurement of B0 → ppKS willhelp to determine the role of the spectator quark in b → sdecays with baryons, while observation of B+ → ppπ+

will constrain the ratio of the b → u tree and b → spenguin diagrams in decays with baryons.

For B0 → ppKS, after the application of the charm

and Λc vetoes, no significant signal is observed in ei-ther the ∆E or Mbc distribution. A fit to the ∆E dis-tribution gives 6.4+4.4

−3.7 events. Applying the Feldman-Cousins procedure [13], we obtain an upper limit ofless than 16 events at the 90% confidence level (C.L.).After reducing the detection efficiency by the system-atic error, we obtain an upper limit at 90% C.L. ofB(B0 → ppK0) < 7.2 × 10−6.

In the B+ → ppπ+ mode, after the application ofthe charm veto we perform a fit to the ∆E distributionthat allows for B+ → ppπ+ signal and a reflection frommisidentified B+ → ppK+ decays. This fit gives a signalyield of 16.2+8.6

−8.0 events and a significance of 2.1σ. Theexcess in the ∆E fit corresponds to a branching fractionB(B+ → ppπ+) = (1.9+1.0

−0.9±0.3)×10−6 or an upper limitof B(B+ → ppπ+) < 3.7 × 10−6 at 90% C.L. after takinginto account the systematic error.

We have observed a significant signal (5.6σ) for thedecay B+ → ppK+. This is the first b → s decay modewith baryons in the final state. In the future, this modecan be used to search for direct CP violation [2]. Wefind that its pp mass spectrum is inconsistent with phasespace and is peaked toward low mass. This feature is sug-gestive of quasi two-body decay. It is also possible thatthe decay is a genuine three-body process and that thisfeature of the M(pp) spectrum is a baryon form factoreffect [14,15].

We wish to thank the KEKB accelerator group for theexcellent operation of the KEKB accelerator. We ac-knowledge support from the Ministry of Education, Cul-ture, Sports, Science, and Technology of Japan and theJapan Society for the Promotion of Science; the Aus-tralian Research Council and the Australian Departmentof Industry, Science and Resources; the National Sci-ence Foundation of China under contract No. 10175071;the Department of Science and Technology of India; theBK21 program of the Ministry of Education of Koreaand the CHEP SRC program of the Korea Science andEngineering Foundation; the Polish State Committee forScientific Research under contract No. 2P03B 17017; theMinistry of Science and Technology of the Russian Fed-eration; the Ministry of Education, Science and Sportof Slovenia; the National Science Council and the Min-istry of Education of Taiwan; and the U.S. Departmentof Energy.

[1] Hereafter, the inclusion of the charge conjugate mode isimplied.

[2] G. Eilam, M. Gronau, and J. Rosner, Phys. Rev. D 39,819 (1989).

[3] X. Fu et al. (CLEO Collaboration), Phys. Rev. Lett. 79,

5

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Short historyB factories

2002: First observation of a baryonic B decay [Phys. Rev. Lett. 88 (2002)181803]Observation and study of many B0 and B+ baryonic decays, both withcharm in the final state and charmlessObserved threshold enhancement in baryon-antibaryon invariant massof several decays

LHCb2013: First observation of 2-body charmless baryonic modeB+ → pΛ(1520) and first evidence of CP violation in a baryonic B decayseen in B+ → ppK+ [Phys. Rev. Lett. 113, 141801 (2014)]2013: First evidence of the very suppressed B0 → pp [J. High Energy Phys.10 (2013) 005]2014: First observation of a baryonic B+

c decay (B+c → J/ψppπ+) [Phys.

Rev. Lett. 113, 152003 (2014)]

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Observation of theB0

s → pΛK− decay

[LHCb-CONF-2016-016]

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Analysis strategy [LHCb-CONF-2016-016]

Goal: Observe first B0s baryonic decay

I Look for three-body decay as larger BF expected than 2-body

Signal: B0s → pΛK−

Normalisation mode: B0 → pΛπ−

Bsgn

Bnorm=

fd

fs

Nsgn

Nnorm

εnorm

εsgn

Dataset: LHCb Run I dataset(3 fb−1), divided per year andreconstruction categorySelection: neural networkagainst combinatorialbackground, particleidentification criteria on chargedhadrons

[JINST 10 (2015) P02007]

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Fit [LHCb-CONF-2016-016]

Perform a simultaneous fit to signal (B0s → pΛK−) and normalisation

mode (B0 → pΛπ−) for all categoriesI Share shape parametersI Constrain cross-feed background from different final states

Backgrounds considered: combinatorial, B0s → pΣK−, B0 → pΣπ−

m(pΛπ) [MeV/c2]

LHCbPreliminary

4900 5000 5100 5200 5300 5400 5500 5600

Can

didates/(15

MeV/c

2)

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m(pΛK) [MeV/c2]

LHCbPreliminary

4900 5000 5100 5200 5300 5400 5500 5600

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didates/(15

MeV/c

2)

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Observe B0s → pΛK− with statistical significance> 15σ

(260± 21 signal candidates from the fit to all the categories)

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Results [LHCb-CONF-2016-016]

First observation of a baryonic B0s decay!

Branching fraction measured to be

B(B0s + B0

s → pΛK−) = [ 5.48+0.82−0.80(stat)±0.60(syst)

±0.51(Bnorm) ±0.32(fs/fd)]× 10−6

Observed threshold enhancement in pp mass spectra (backgorundsubtracted)

m(pΛ) [ GeV/c2]2.5 3 3.5 4 4.5 5S

um

ofsW

eigh

ts/(20MeV/c

2)

LHCbPreliminary

0

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m(pΛ) [ GeV/c2]2.5 3 3.5 4 4.5S

um

ofsW

eigh

ts/(20MeV/c

2)

LHCbPreliminary

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B0s → pΛK−

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Observation of theB0(s)→ pph+h′− decays

[LHCb-PAPER-2017-005, In preparation]

New

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Analysis strategy [LHCb-PAPER-2017-005, In preparation]

Goal: Observe and measure BF of charmless B0(s)→ pph+h′− modes

I Only known B(B0→ ppK∗0) = (1.24+0.28−0.25)× 10−6 (BaBar and Belle)

Signal: B0(s)→ pph+h′− (h(′) = K or π)

I Excluding the charmonium region: m(pp) < 2.85 GeVI Veto D0 andΛc

Normalisation mode: B0→ (J/ψ→ pp)(K∗0→ K+π−), same selectionas signal except charm vetoesDataset: LHCb Run I dataset (3 fb−1)Selection: BDT against combinatorial background, particleidentification on hadrons (each candidate only in one final statesample)Simultaneous fit to invariant mass of 3 final states3-D fit in m(ppK±π∓), m(pp) and m(K±π∓) for normalisation mode

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Simultaneous signal fits [LHCb-PAPER-2017-005, In preparation]

]2 [MeV/cKK)pm(p5200 5300 5400 5500

)2C

andi

date

s / (

8 M

eV/c

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KKp p→ 0B

KKp p→ s0B

πKp p→ 0BComb. bkgd.

LHCbPreliminary

]2 [MeV/c)πKpm(p5200 5300 5400 5500

)2C

andi

date

s / (

5 M

eV/c

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πKp p→ 0B

πKp p→ s0B

ππp p→ 0BComb. bkgd.

LHCbPreliminary

nppK+K−

B = 68± 17 nppK+K−

Bs= 635± 32

nppK±π∓

B = 4155± 83 nppK±π∓

Bs= 246± 39

nppπ+π−

B = 902± 35 nppπ+π−

Bs= 39± 16

First strong evidence First observations

]2 [MeV/c)ππpm(p5200 5300 5400 5500

)2C

andi

date

s / (

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MeV

/c

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ππp p→ 0B

ππp p→ s0B

πKp p→ 0BComb. bkgd.

LHCbPreliminary

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Substructures in m(h+h′−) [LHCb-PAPER-2017-005, In preparation]

B0s → ppK+K−

]2 [MeV/cm(KK)1000 2000 3000

)2 W

eigh

ted

cand

idat

es/(

40 M

eV/c

0

0.01

0.02

0.03

0.04

0.05LHCbPreliminary

B0→ ppK±π∓

]2 [MeV/c)πm(K1000 2000 3000

)2 W

eigh

ted

cand

idat

es/(

80 M

eV/c

0

0.01

0.02

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0.09 LHCbPreliminary

Efficiency-corrected andbackground-subtractedVector mesons visible(φ(1020), K∗(892)0, ρ0(770))

B0→ ppπ+π−

]2 [MeV/c)ππm(1000 2000 3000

)2 W

eigh

ted

cand

idat

es/(

80 M

eV/c

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0.01

0.02

0.03

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0.05

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0.07

0.08LHCbPreliminary

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Threshold enhancement in m(pp) [LHCb-PAPER-2017-005]

B0s → ppK+K−

]2 [MeV/c)pm(p2000 2500 3000

)2 W

eigh

ted

cand

idat

es/(

50 M

eV/c

0

0.02

0.04

0.06

0.08

0.1

0.12 LHCbPreliminary

B0→ ppK±π∓

]2 [MeV/c)pm(p2000 2500 3000

)2 W

eigh

ted

cand

idat

es/(

50 M

eV/c

0

0.02

0.04

0.06

0.08

0.1

0.12 LHCbPreliminary

Efficiency-corrected andbackground-subtractedClear threshold enhancement

B0→ ppπ+π−

]2 [MeV/c)pm(p2000 2500 3000

)2 W

eigh

ted

cand

idat

es/(

50 M

eV/c

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14LHCbPreliminary

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Results [LHCb-PAPER-2017-005, In preparation]

3 first observations and a strong evidence

Decay channel Significance [σ] Branching fraction / 10−6

B0→ ppK+K− 4.1 0.126±0.031±0.013±0.006B0→ ppK±π∓ > 25 6.6 ±0.3 ±0.3 ±0.3B0→ ppπ+π− > 25 3.0 ±0.2 ±0.2 ±0.1B0

s → ppK+K− > 25 4.6 ±0.3 ±0.3 ±0.2 ±0.3B0

s → ppK±π∓ 6.5 1.45 ±0.24 ±0.12 ±0.07 ±0.08B0

s → ppπ+π− 2.6 0.46 ±0.19 ±0.05 ±0.02 ±0.03

val± stat± syst± σ(B)± σ(fs/fd)

Upper limit set on B(B0s → ppπ+π−)

B(B0s → ppπ+π−) < 7.3× 10−7 at 90% CL

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CP violation in b decays

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Time dependent CPviolation in the

B0 → π+π− andB0

s → K+K− decays

[LHCb-CONF-2016-018]

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Motivations [LHCb-CONF-2016-018]

Time dependent asymmetries linked to CPV parameters Cf , Sf and A∆Γf

A(t) =Γ

B0(s)→f

(t) − ΓB0(s)→f(t)

ΓB

0(s)→f

(t) + ΓB0(s)→f(t)

=−Cf cos(∆md,st) + Sf sin(∆md,st)

cosh(∆Γd,s

2 t)+ A∆Γ

f sinh(∆Γd,s

2 t)

|Cf |2 + |Sf |

2 + |A∆Γf |2 = 1

Rich set of physics processes contributes to B0→ π+π− andB0

s → K+K− decays (Tree and penguin contributions, neutral B mixing,possible new physics in loops)Time dependent CPV sensitive to CKM phases

I angles γ and βs measured in [Phys. Lett. B 741 (2015) 1]

Cπ+π− and Sπ+π− well constrained by B-factories and LHCbCK+K− and SK+K− measured only by LHCb using 1 fb−1 (2011) and nomeasurement for A∆Γ

K+K− [JHEP 10 (2013) 183]

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Analysis strategy [LHCb-CONF-2016-018]

BDT against combinatorial background, particle identificationselection to reduce contamination from other B→ hh′ modes to∼ 10% of the signal.CPV coefficients determined from unbinned maximum likelihood fitto

I Mass, decay time, per-event mistag probability, per-event decay timeerror

I Simultaneous fit to π+π−, K+K− and K+π− mass spectra

Production asymmetry determined from B0 → K+π− andB0

s → K−π+

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Analysis strategy [LHCb-CONF-2016-018]

Mistag probability and decay time resolution dilute amplitude of timedependent asymmetries

Use opposite side taggers calibrated using B0 → K+π−

Determine per-event decay time resolution from decay time errorcomputed in reconstruction calibrated with B0 → K+π− andB0

s → D+s π

+

PV

pp

X

X

X

SVSS pion SS proton SS kaon

K+

OS vertex charge OS charm

SV

b → c b → X l–

c → s

OS kaon

OS muon OS electron

TV

same sideopposite side

b

bq

q

quX–

l–

K–

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Results [LHCb-CONF-2016-018]

Resultsofthesimultaneousfit

19

p+p- spectrum(LHCb Preliminary)

LHCb

-CON

F-20

16-018

statisticalerroronly

Resultofthesimultaneousfit

21

K+K- spectrum(LHCb Preliminary)

LHCb

-CON

F-20

16-018

statisticalerroronly

Cπ+π− = −0.24±0.07±0.01

Sπ+π− = −0.68±0.06±0.01

CK+K− = 0.24±0.06±0.02

SK+K− = 0.22±0.06±0.02

A∆ΓK+K− = −0.75±0.07±0.11

val± stat± syst

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Results [LHCb-CONF-2016-018]

Results in agreement with [JHEP 10 (2013) 183] and approximatelytwice more preciseNaive CPV significance (neglect correlations and sum in quadrature)

I (CK+K− , SK+K− ,A∆ΓK+K−) is 4.7σ from (0,0, 1)

I (CK+K− , SK+K−) is 4.6σ from (0,0)I CK+K− and SK+K− are 3.6σ and 3.3σ from 0 respectively

First evidence of CPV in B0s → K+K− decay

Best measurement of Sπ+π− from a single experimentUpdate also with same sign taggers will follow soon

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Evidence for CP violationinΛ0

b→ pπ−π+π−

[Nat. Phys. (2017)]

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Motivations [Nat. Phys. (2017)]

CPV predicted by SM in baryons but not observed yetInΛ0

b → pπ−π+π− tree and penguin diagrams have similar amplitudeLocal CPV in multibody decays can be larger that global CPVPossible to use T-odd observables (triple products)

CT = ~pp ·(~pπ−

fast×~pπ+

)∝ sinΦ

AT =N(CT > 0) − N(CT < 0)

N(CT > 0) + N(CT < 0)

AT =N(−CT > 0) − N(−CT < 0)

N(−CT > 0) + N(−CT < 0)

CP-violating observable

aT−oddCP =

12(AT −AT

)P-violating observable

aT−oddP =

12(AT +AT

)

0

�⇡+

⇡�slow ⇡�

fast

p

Giulio Dujany (Manchester) Charmless b-hadron decays La Thuile 2017 25 / 37

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Analysis strategy [Nat. Phys. (2017)]

Search for CPV inΛ0b → pπ−h+h′− (h(′) = K or π) using triple

productsUseΛ0

b → (Λ+c → pK−π+)π− where no CPV is expected as control

modeSimultaneous fit to m(pπ−h+h′−)

N(Λ0b → pπ−π+π−) = 6646± 105 (stat)

]2c) [GeV/−π+π−πp(m5.2 5.4 5.6 5.8 6

)2 cE

vent

s/(9

MeV

/

0

500

1000

1500

Full fit−π+π−πp →0

bΛPart-rec. bkg.Comb. bkg.

+π−π−π+K →0B−π+π−pK →0

LHCb

(a)

N(Λ0b → pπ−K+K−) = 1030± 56 (stat)

]2c) [GeV/−K+K−πp(m5.2 5.4 5.6 5.8 6

)2 cE

vent

s/(9

MeV

/

0

200

400

Full fit−K+K−πp →0

bΛPart-rec. bkg.Comb. bkg.

−π+K+K−K →0B+π−π+K−K →0

sB−K−K+pK →0

bΛ−π+π−pK →0

LHCb

(b)

Giulio Dujany (Manchester) Charmless b-hadron decays La Thuile 2017 26 / 37

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CPV measurement [Nat. Phys. (2017)]

Global CPV: Results compatible with P andCP conservation conservationLocal CPVΛ0

b → pπ−K+K−: Limited yielddivide only in two bins in m(pK−).Compatible with P and CP conservationLocal CPVΛ0

b → pπ−π+π−: Use twodifferent binning schemes:

I Scheme A: 12 regions dominated by2-body resonances (ρ0(770), ∆++, N∗)

I Scheme B: 10 uniform bins inΦI P symmetry compatible at 2.2σI 3.3σ evidence for CPV found combining

both schemes

Asy

mm

etri

es [

%]

Phase space bin5 10

20 0

20− /ndf=21.1/122χ CP

-oddTa

5 10

20 0

20−

LHCb Scheme A

/ndf=27.9/122χ P-oddTa

Asy

mm

etri

es [

%]

| [rad]Φ|1 2 3

20 0

20− /ndf=30.5/102χ CP

-oddTa

1 2 3

20 0

20−

LHCb Scheme B

/ndf=20.7/102χ P-oddTa

Giulio Dujany (Manchester) Charmless b-hadron decays La Thuile 2017 27 / 37

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Rare B decays

Giulio Dujany (Manchester) Charmless b-hadron decays La Thuile 2017 28 / 37

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Search for the B0s → η′φ

decay

[arXiv:1612.08110, Submitted to JHEP]

Giulio Dujany (Manchester) Charmless b-hadron decays La Thuile 2017 29 / 37

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Motivations [arXiv:1612.08110, Submitted to JHEP]

Proceeds via b→ sss penguin transition likeB0

s → φφ and B0s → η′η′

Predictions cover wide range and have biguncertainties due to limited knowledge onform factors, penguin contributions,ω–φmixing angle and s-quark mass

b s

s s

s

s

W

u, c, tφ, η′

η′, φ

B0s

Theory approach Yield B/10−6 Reference

QCD factorisation 0.05+1.18−0.19 [Nucl.Phys. B 675 (2003) 333-415]

QCD factorisation 2.2+9.4−3.1 [arXiv:hep-ph/0701146]

Perturbative QCD 0.19+0.20−0.13 [Phys.Rev. D 76 (2007) 074018]

Perturbative QCD 20.0+16.3−9.1 [Phys.Rev. D 80 (2009) 114026]

SCET 4.3+5.2−3.6 [Phys.Rev. D 78 (2008) 034011]

SU(3) flav. symm. 5.5± 1.8 [Phys.Rev.D 91 (2014) 014011]

FAT 13.0± 1.6 [arXiv:1608.02819]

Giulio Dujany (Manchester) Charmless b-hadron decays La Thuile 2017 30 / 37

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Analysis strategy [arXiv:1612.08110, Submitted to JHEP]

Signal: B0s → η′φ

Normalisation mode: B+ → η′K+ (B = (70.6± 2.5)× 10−6)Reconstruct η′ candidates as η′ → π+π−γ

Dataset: LHCb Run I dataset (3 fb−1)Blinded until selection strategy finalisedFit: 2D (m(η′K+K−), m(π+π−γ)) and simultaneous for signal andnormalisation modeSensitivity: expected> 5σ (40 events) for B = 4× 10−6

Giulio Dujany (Manchester) Charmless b-hadron decays La Thuile 2017 31 / 37

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Results [arXiv:1612.08110, Submitted to JHEP]

]2 [MeV/cγππm900 950 1000

)2

Candid

ate

s/(8

MeV

/c

0

10

20

30

40

50 LHCb

signal B0s → φφ(π+π−π0) combinatorial comb. with real η′

No indication of the signal (N(B0s → η′φ) = −3.2+5.0

−3.8 )Set upper limit on branching fraction

B(B0s → η′φ) < 0.82(1.01)× 10−6 at 90% (95%) CL

Most central values of theoretical predictions significantly larger

Giulio Dujany (Manchester) Charmless b-hadron decays La Thuile 2017 32 / 37

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Observation of theB0→ K+K− decay

[Phys. Rev. Lett. 118 (2017) 081801]

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Motivations [Phys. Rev. Lett. 118 (2017) 081801]

B0 → K+K− and B0s → π+π− proceed via

weak annihilation transitions (all final statequarks different from initial state)Highly suppressed but possibleenhancement from rescattering effectsB0 → K+K− unobserved so far,B0

s → π+π− observed in [JHEP 1210 (2012)037]

Precise BF measurement for the two modesprovides input to improve knowledge ofQCD dynamics in B0

(s) → h+h′−

b

d, s

W

s, d

s, d

u

u

W

b

d, s

s, d

s, d

u

u

Giulio Dujany (Manchester) Charmless b-hadron decays La Thuile 2017 34 / 37

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Analysis strategy [Phys. Rev. Lett. 118 (2017) 081801]

Signal: B0 → K+K− and B0s → π+π−

Normalisation mode: B→ K+π−

Dataset: LHCb Run I dataset (3 fb−1)Blinded until selection strategy finalisedSelection: BDT against combinatorial background, particleidentification criteria on charged hadronsFit: Simultaneous fit to 2-body invariant mass of several mutuallyexclusive subsamples (K+π−, pK−, pπ−, π+π− and K+K−)

Giulio Dujany (Manchester) Charmless b-hadron decays La Thuile 2017 35 / 37

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Results [Phys. Rev. Lett. 118 (2017) 081801]

5.2 5.4 5.6 5.8

)2

cC

an

did

ate

s / (

5 M

eV

/

0

50

100

150

­K

+ K→

0B

­K+ K→

0sB

­π

+ K→

0B

­ pK→

0bΛ

K+ K→0sB

Comb. bkg.

LHCb

]2c [GeV/­

K+

Km

5.2 5.4 5.6 5.8

Pu

ll

­4­2024 5 5.2 5.4 5.6 5.8

)2

cC

an

did

ate

s / (

5 M

eV

/

0

100

200

300

400

­π

+π →

0sB

­π

+π →

0B

­π

+ K→

0B

X­π+

π →0

B

Comb. bkg.

LHCb

]2c [GeV/­

π+

πm

5 5.2 5.4 5.6 5.8P

ull

­4­2024

B0 → K+K−

observed at 5.8σ

Measured BF(World’s mostprecise)

B(B0 → K+K−) = [7.80± 1.27(stat)±0.81(syst)±0.21(Bnorm)]× 10−8

B(B0s → π+π−) = [6.91±0.54(stat)±0.63(syst)±0.19(Bnorm)±0.40(fs/fd)]× 10−7

In agreement within uncertainties with pQCD [Phys. Rev. D 85 (2012)094003]

Agreement for B(B0 → K+K−) but significantly largerB(B0

s → π+π−) than QCDF [Phys. Rev. D 80 (2009) 114026]

Giulio Dujany (Manchester) Charmless b-hadron decays La Thuile 2017 36 / 37

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Conclusion

Presented several recent results from the LHCb collaboration:First observation of baryonic Bs decayFirst observation of 3 new B0

(s)→ pph+h′− modes and evidence of afourth one New!First evidence of CPV in B0

s → K+K− (with naive treatment of errors)First evidence of CPV in baryonsWorld’s best limit on B0

s → η′φ

First observation of B0→ K+K− rarest hadronic B decay everobserved!

Giulio Dujany (Manchester) Charmless b-hadron decays La Thuile 2017 37 / 37

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BACKUP

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LHCb [Int. J. Mod. Phys. A 30 (2015) 1530022]

Acceptance: 2 < η < 5∼ 1/4 of produced bb pairs.

Decay timeresolution ∼ 45 fs

IP resolution ∼ 20µm

Vertex resolution ∼ 13µmin x y (25 tracks)

∆p/p ∼ 0.5 − 1.0%

ε(µ) ∼ 97%,misID(π→ µ) ∼ 1 − 3%

ε(K) ∼ 95%,misID(π→ K) ∼ 5%

Giulio Dujany (Manchester) Charmless b-hadron decays La Thuile 2017 39

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ReconstructingΛ and K0s [Int. J. Mod. Phys. A 30 (2015) 1530022]

Long

Downstream

Giulio Dujany (Manchester) Charmless b-hadron decays La Thuile 2017 40