φ1 Measurements at Belle

Nuclear Physics B Proceedings Supplement 00 (2014) 1–4

Nuclear Physics B Proceedings Supplement

φ

Measurements at Belle

Veronika Chobanova

Max-Planck-Institut f¨ur Physik D-80805 M¨unchen, Germany

Abstract

We present the recent measurements of theB⁰→η⁰K⁰and theB→ωKdecay modes based on the full data set of 772×10⁶BB¯pairs collected by the Belle detector at the KEKBe⁺e⁻collider. In theB⁰→η⁰K⁰mode, we obtain the CP-violating parameters

A_η0K⁰ = +0.03±0.05 (stat)±0.04 (syst), S_η0K⁰ = +0.68±0.07 (stat)±0.03 (syst).

This is the world’s most precise result on theη⁰K⁰CPparameters. InB → ωKdecays, we measure the branching fractions

B_B0→ωK⁰ = (4.5±0.4 (stat)±0.3 (syst))×10⁻⁶, B_B⁻_→ωK⁻ = (6.8±0.4 (stat)±0.4 (syst))×10⁻⁶,

which are their current most precise results. We measure the first evidence ofCPviolation in theB⁰ → ωK_S⁰ decay mode, obtaining theCP-violating parameters

A_ωK0

S = −0.36±0.19 (stat)±0.05 (syst), S_ωK0

S = +0.91±0.32 (stat)±0.05 (syst).

In theB⁻→ωK⁻mode, we measure the directCP-violation parameter A_ωK−=−0.03±0.04 (stat)±0.01 (syst),

which is its most precise measurement to date.

Keywords: CPviolation, hep, Belle

1. Introduction

The main purpose of theBfactories, Belle and BaBar, was to test the Cabibbo-Kobayashi-Maskawa (CKM) mechanism, which is a part of the Standard Model of particle physics (SM). The CKM mechanism foresees the existence of aCP-violating complex phase in the quark sector that gives rise toCPviolation. TheBfacto- ries measured the angles,φ1,φ2andφ3, and the sides of

the unitarity triangle forBmesons, the area of which is proportional to the SMCP-violating phase. In the past decade, measurements of the sin 2φ₁value inb → c¯cs transitions confirmed the CKM mechanism predictions.

Despite the great success of the CKM theory, it fails to explain the magnitude of the matter-antimatter asym- metry in today’s Universe. Thus, attention has turned towards search for new sources ofCPviolation, intro-

/Nuclear Physics B Proceedings Supplement 00 (2014) 1–4 2

duced by new physics. Decays of theBmeson that pro- ceed predominantly through loop-dominatedb → sqq¯ transitions are highly sensitive to heavy particle con- tributions in the loop, which can be introduced by so far undetected particles. The decays presented in these proceedings, B⁰ → η⁰K⁰ andB → ωK, fall into this category. They are both sensitive toφ1, which can be accessed by measuring their time-dependentCPasym- metries.

The B factories operate at the Υ(4S) resonance, which decays almost exclusively into a BB¯ pair. For flavour tagging of aBmeson of interest, we use flavour- specific decays of the otherBmeson in the pair, the so- called “tag side”. The time-dependentCPasymmetry for aBdecay into a givenCPfinal state f, is given by

aCP(∆t)=A_fcos∆md∆t+S_fsin∆md∆t,

where∆tis the difference in the decay time of the two Bmesons produced in theΥ(4S) decay,∆md is the dif- ference between the masses of the heavy and light mass eigenstates of theB⁰meson, andA_f andS_f are theCP- violating parameters. Assuming only a loop contribu- tion inη⁰K⁰ and inωK_S⁰, we expectS_f =−ξ_fsin 2φ₁, whereξ_f = ±1 is theCPeigenvalue of the final state.

Due to pollution by lower-order processes, the mea- sured S_f value deviates from this expectation by an amount∆S_f =S_f −sin 2φ1that depends on the decay channel .

We present the measurements of theB⁰ → η⁰K⁰and B→ωK CP-asymmetry parameters, along with a mea- surement of theB→ωKbranching fractions, based on the full Belle [1] data set containing 772 millions BB¯ pairs.

2. Measurement ofCP violation parameters in the B⁰ →η⁰K⁰decay

In theB⁰→η⁰K⁰decay channel, the Standard Model predicts−0.05≤∆S_η0K⁰≤0.09 [2]. TheCPparameters of the twoCPfinal statesη⁰K_S⁰ andη⁰K⁰_Lare measured separately and in the end combined to a common value, since they are equal according to the theory.

After the event reconstruction, we estimate the sig- nal yield. For this, in theη⁰K_S⁰ decay mode, we fit the event distributions of the beam-constrained mass of the BmesonMbc, the difference between the reconstructed B meson energy and the beam energy ∆E and a qq-¯ background suppression likelihood ratioR_s/b, based on event-shape variables. In theη⁰K⁰_Ldecay mode, we ex- tract the signal yield by fittingR_s/band theBmeson mo- mentum, reconstructed with the knowledge of the beam

s✐❞❡❜❛♥❞ r❡❣✐♦♥ ✭0.92●❡❱✴c²< Mη′<0.93●❡❱✴c²✱0.97●❡❱✴c²< Mη′<1.00●❡❱✴c²✮✳

❚❤❡ P❉❋ s❤❛♣❡ ✐s ❞❡t❡r♠✐♥❡❞ ❛♥❞ t❤❡ ✜t ✐s ♣❡r❢♦r♠❡❞ ❢♦r ❡❛❝❤ ❞❡❝❛② ♠♦❞❡✱KL⁰❝❛♥❞✐❞❛t❡

❝❛t❡❣♦r②✱ ❛♥❞ t❛❣❣✐♥❣✲q✉❛❧✐t② ✐♥t❡r✈❛❧ s❡♣❛r❛t❡❧②✳ ❚❤❡ ✜t r❛♥❣❡ ✉s❡❞ ❢♦r t❤❡ ✜t ✐s ❣✐✈❡♥ ❜② p^∗B<2●❡❱✴c❛♥❞Rs/b>0.5✳ ❚❤❡ r❡❝♦♥str✉❝t❡❞B❝❛♥❞✐❞❛t❡ ❞✐str✐❜✉t✐♦♥s ✐♥p^∗B❛♥❞

Rs/b✇✐t❤ t❤❡ ❝♦rr❡s♣♦♥❞✐♥❣ ♦♥❡ ❞✐♠❡♥s✐♦♥❛❧ ♣r♦❥❡❝t✐♦♥s ♦❢ t❤❡ ✜tt❡❞ ♠♦❞❡❧ ❛r❡ s❤♦✇♥ ✐♥

✜❣✉r❡✷✳

■♥ t❛❜❧❡✷✇❡ s✉♠♠❛r✐③❡ t❤❡ ♦❜t❛✐♥❡❞ s✐❣♥❛❧ ②✐❡❧❞s ❛♥❞ s❛♠♣❧❡ ♣✉r✐t✐❡s ❢♦r ❛❧❧ r❡❝♦♥✲

str✉❝t❡❞ ❞❡❝❛② ♠♦❞❡s✳ ❋♦r ♠♦❞❡s ✇✐t❤K⁰St❤❡ s✐❣♥❛❧ r❡❣✐♦♥ ❝♦♥t❛✐♥s t❤❡ ❢✉❧❧Rs/br❛♥❣❡✱

s♦ ✇❡ s❤♦✇ ❛❧s♦ t❤❡ s❛♠♣❧❡ ♣✉r✐t② ✐♥ t❤❡ r❡❣✐♦♥ ❝♦♥str❛✐♥❡❞ ❜②Rs/b>0.75✳ ❚❤✐s r❡❣✐♦♥

❝♦♥t❛✐♥s ❛❜♦✉t70%♦❢ t❤❡ s✐❣♥❛❧ ❝❛♥❞✐❞❛t❡s✳ ■♥ t♦t❛❧ ✇❡ r❡❝♦♥str✉❝t3941±90s✐❣♥❛❧ ❝❛♥✲

❞✐❞❛t❡s✱ ✇❤❡r❡ t❤❡ ✉♥❝❡rt❛✐♥t② ✐s st❛t✐st✐❝❛❧ ♦♥❧②✳ ❈♦♠♣❛r❡❞ t♦ ♦✉r ♣r❡✈✐♦✉s ♠❡❛s✉r❡♠❡♥t

❬✶✹❪ ✇❡ ♦❜s❡r✈❡ ❛♥ ✐♥❝r❡❛s❡ ♦❢ ❛❜♦✉t20%✐♥ t❤❡ ❡✈❡♥t r❡❝♦♥str✉❝t✐♦♥ ❡✣❝✐❡♥❝②✱ ✇❤✐❝❤ ✐s

❞✉❡ t♦ ❛♥ ✐♥❝r❡❛s❡ ✐♥ t❤❡ tr❛❝❦ r❡❝♦♥str✉❝t✐♦♥ ❡✣❝✐❡♥❝②✱ ❛ ♥❡✇K_S⁰s❡❧❡❝t✐♦♥ ♠❡t❤♦❞✱ ❛♥❞ ❛ r❡✲♦♣t✐♠✐③❛t✐♦♥ ♦❢ t❤❡ ❡✈❡♥t s❡❧❡❝t✐♦♥ ❝r✐t❡r✐❛✳

[GeV]

Mbc 5.23 5.24 5.25 5.26 5.27 5.28 5.29

Entries / 0.0026 GeV

0 200 400 600 800

E [GeV]

∆ -0.2 -0.15-0.1 -0.05 0 0.050.10.150.2

Entires / 0.015 GeV

100 200 300 400 500 600

Rs/b

0 0.2 0.4 0.6 0.8 1

Entries / 0.05

200 400 600 800 1000 1200 1400

❋✐❣✉r❡ ✶✳Mbc,∆E❛♥❞Rs/b❞✐str✐❜✉t✐♦♥s ♦❢B❝❛♥❞✐❞❛t❡s r❡❝♦♥str✉❝t❡❞ ✇✐t❤K_S⁰✭❞❛t❛ ♣♦✐♥ts✮✳

❚❤❡Mbc❞✐str✐❜✉t✐♦♥ ✐s s❤♦✇♥ ❢♦r t❤❡ ❝❛♥❞✐❞❛t❡s ✇✐t❤✐♥ t❤❡∆Es✐❣♥❛❧ r❡❣✐♦♥ ❛♥❞ ✇✐t❤Rs/b>0.7✱

t❤❡∆E❞✐str✐❜✉t✐♦♥ ❢♦r t❤❡ ❝❛♥❞✐❞❛t❡s ✇✐t❤✐♥ t❤❡Mbcs✐❣♥❛❧ r❡❣✐♦♥ ❛♥❞ ✇✐t❤Rs/b>0.7✱ ❛♥❞ t❤❡

Rs/b❞✐str✐❜✉t✐♦♥ ✐s s❤♦✇♥ ❢♦r t❤❡ ❝❛♥❞✐❞❛t❡s ✇✐t❤✐♥ t❤❡Mbc−∆Es✐❣♥❛❧ r❡❣✐♦♥✳ ❚❤❡ r❡❞ s♦❧✐❞ ❧✐♥❡s s❤♦✇ t❤❡ ❝♦rr❡s♣♦♥❞✐♥❣ ♦♥❡ ❞✐♠❡♥s✐♦♥❛❧ ♣r♦❥❡❝t✐♦♥s ♦❢ t❤❡ ✜tt❡❞ ♠♦❞❡❧ ✭s✐❣♥❛❧✰❜❛❝❦❣r♦✉♥❞✮✱ t❤❡

②❡❧❧♦✇ ❛♥❞ ❜❧✉❡ ❛r❡❛s s❤♦✇ t❤❡ ❝♦♥tr✐❜✉t✐♦♥s ❢r♦♠ t❤❡ ❝♦♥t✐♥✉✉♠ ❛♥❞BB¯❜❛❝❦❣r♦✉♥❞✱ r❡s♣❡❝t✐✈❡❧②✳

0 0.5 1 1.5 2

counts/50MeV/c

0 100 200 300

0.5 0.6 0.7 0.8 0.9 1

counts/0.02

0 100 200 300 400

❋✐❣✉r❡ ✷✳ p^∗_B❛♥❞Rs/b❞✐str✐❜✉t✐♦♥s ♦❢B❝❛♥❞✐❞❛t❡s r❡❝♦♥str✉❝t❡❞ ✇✐t❤K_L⁰✭❞❛t❛ ♣♦✐♥ts✮✳

❚❤❡ r❡❞ s♦❧✐❞ ❧✐♥❡s s❤♦✇ t❤❡ ❝♦rr❡s♣♦♥❞✐♥❣ ♦♥❡ ❞✐♠❡♥s✐♦♥❛❧ ♣r♦❥❡❝t✐♦♥s ♦❢ t❤❡ ✜tt❡❞ ♠♦❞❡❧ ✭s✐❣✲

♥❛❧✰❜❛❝❦❣r♦✉♥❞✮✳ ❚❤❡ ❜❧✉❡✱ ❣r❡❡♥✱ ❛♥❞ ②❡❧❧♦✇ ❛r❡❛s s❤♦✇ t❤❡ ❝♦♥tr✐❜✉t✐♦♥s ❢r♦♠ t❤❡ ❝♦♥s✐❞❡r❡❞

❜❛❝❦❣r♦✉♥❞ ❝❛t❡❣♦r✐❡s✿ ❢❛❦❡η^′✱ r❡❛❧η^′✇✐t❤ ❢❛❦❡K⁰_L✱ ❛♥❞ r❡❛❧η^′✇✐t❤ r❡❛❧K_L⁰✱ r❡s♣❡❝t✐✈❡❧②✳

✕ ✽ ✕

s✐❞❡❜❛♥❞ r❡❣✐♦♥ ✭0.92●❡❱✴c²< Mη′<0.93●❡❱✴c²✱0.97●❡❱✴c²< Mη′<1.00●❡❱✴c²✮✳

❚❤❡ P❉❋ s❤❛♣❡ ✐s ❞❡t❡r♠✐♥❡❞ ❛♥❞ t❤❡ ✜t ✐s ♣❡r❢♦r♠❡❞ ❢♦r ❡❛❝❤ ❞❡❝❛② ♠♦❞❡✱K⁰_L❝❛♥❞✐❞❛t❡

❝❛t❡❣♦r②✱ ❛♥❞ t❛❣❣✐♥❣✲q✉❛❧✐t② ✐♥t❡r✈❛❧ s❡♣❛r❛t❡❧②✳ ❚❤❡ ✜t r❛♥❣❡ ✉s❡❞ ❢♦r t❤❡ ✜t ✐s ❣✐✈❡♥ ❜② p^∗_B<2●❡❱✴c❛♥❞Rs/b>0.5✳ ❚❤❡ r❡❝♦♥str✉❝t❡❞B❝❛♥❞✐❞❛t❡ ❞✐str✐❜✉t✐♦♥s ✐♥p^∗_B❛♥❞

Rs/b✇✐t❤ t❤❡ ❝♦rr❡s♣♦♥❞✐♥❣ ♦♥❡ ❞✐♠❡♥s✐♦♥❛❧ ♣r♦❥❡❝t✐♦♥s ♦❢ t❤❡ ✜tt❡❞ ♠♦❞❡❧ ❛r❡ s❤♦✇♥ ✐♥

✜❣✉r❡✷✳

■♥ t❛❜❧❡✷✇❡ s✉♠♠❛r✐③❡ t❤❡ ♦❜t❛✐♥❡❞ s✐❣♥❛❧ ②✐❡❧❞s ❛♥❞ s❛♠♣❧❡ ♣✉r✐t✐❡s ❢♦r ❛❧❧ r❡❝♦♥✲

str✉❝t❡❞ ❞❡❝❛② ♠♦❞❡s✳ ❋♦r ♠♦❞❡s ✇✐t❤KS⁰t❤❡ s✐❣♥❛❧ r❡❣✐♦♥ ❝♦♥t❛✐♥s t❤❡ ❢✉❧❧Rs/br❛♥❣❡✱

s♦ ✇❡ s❤♦✇ ❛❧s♦ t❤❡ s❛♠♣❧❡ ♣✉r✐t② ✐♥ t❤❡ r❡❣✐♦♥ ❝♦♥str❛✐♥❡❞ ❜②Rs/b>0.75✳ ❚❤✐s r❡❣✐♦♥

❝♦♥t❛✐♥s ❛❜♦✉t70%♦❢ t❤❡ s✐❣♥❛❧ ❝❛♥❞✐❞❛t❡s✳ ■♥ t♦t❛❧ ✇❡ r❡❝♦♥str✉❝t3941±90s✐❣♥❛❧ ❝❛♥✲

❞✐❞❛t❡s✱ ✇❤❡r❡ t❤❡ ✉♥❝❡rt❛✐♥t② ✐s st❛t✐st✐❝❛❧ ♦♥❧②✳ ❈♦♠♣❛r❡❞ t♦ ♦✉r ♣r❡✈✐♦✉s ♠❡❛s✉r❡♠❡♥t

❬✶✹❪ ✇❡ ♦❜s❡r✈❡ ❛♥ ✐♥❝r❡❛s❡ ♦❢ ❛❜♦✉t20%✐♥ t❤❡ ❡✈❡♥t r❡❝♦♥str✉❝t✐♦♥ ❡✣❝✐❡♥❝②✱ ✇❤✐❝❤ ✐s

❞✉❡ t♦ ❛♥ ✐♥❝r❡❛s❡ ✐♥ t❤❡ tr❛❝❦ r❡❝♦♥str✉❝t✐♦♥ ❡✣❝✐❡♥❝②✱ ❛ ♥❡✇K⁰_Ss❡❧❡❝t✐♦♥ ♠❡t❤♦❞✱ ❛♥❞ ❛ r❡✲♦♣t✐♠✐③❛t✐♦♥ ♦❢ t❤❡ ❡✈❡♥t s❡❧❡❝t✐♦♥ ❝r✐t❡r✐❛✳

[GeV]

Mbc 5.23 5.24 5.25 5.26 5.27 5.28 5.29

Entries / 0.0026 GeV

0 200 400 600 800

E [GeV]

∆ -0.2 -0.15-0.1 -0.05 0 0.05 0.10.15 0.2

Entires / 0.015 GeV

100 200 300 400 500 600

Rs/b

0 0.2 0.4 0.6 0.8 1

Entries / 0.05

200 400 600 800 1000 1200 1400

❋✐❣✉r❡ ✶✳M_bc,∆E❛♥❞Rs/b❞✐str✐❜✉t✐♦♥s ♦❢B❝❛♥❞✐❞❛t❡s r❡❝♦♥str✉❝t❡❞ ✇✐t❤K⁰_S✭❞❛t❛ ♣♦✐♥ts✮✳

❚❤❡Mbc❞✐str✐❜✉t✐♦♥ ✐s s❤♦✇♥ ❢♦r t❤❡ ❝❛♥❞✐❞❛t❡s ✇✐t❤✐♥ t❤❡∆Es✐❣♥❛❧ r❡❣✐♦♥ ❛♥❞ ✇✐t❤Rs/b>0.7✱ t❤❡∆E❞✐str✐❜✉t✐♦♥ ❢♦r t❤❡ ❝❛♥❞✐❞❛t❡s ✇✐t❤✐♥ t❤❡Mbcs✐❣♥❛❧ r❡❣✐♦♥ ❛♥❞ ✇✐t❤Rs/b>0.7✱ ❛♥❞ t❤❡

Rs/b❞✐str✐❜✉t✐♦♥ ✐s s❤♦✇♥ ❢♦r t❤❡ ❝❛♥❞✐❞❛t❡s ✇✐t❤✐♥ t❤❡Mbc−∆Es✐❣♥❛❧ r❡❣✐♦♥✳ ❚❤❡ r❡❞ s♦❧✐❞ ❧✐♥❡s s❤♦✇ t❤❡ ❝♦rr❡s♣♦♥❞✐♥❣ ♦♥❡ ❞✐♠❡♥s✐♦♥❛❧ ♣r♦❥❡❝t✐♦♥s ♦❢ t❤❡ ✜tt❡❞ ♠♦❞❡❧ ✭s✐❣♥❛❧✰❜❛❝❦❣r♦✉♥❞✮✱ t❤❡

②❡❧❧♦✇ ❛♥❞ ❜❧✉❡ ❛r❡❛s s❤♦✇ t❤❡ ❝♦♥tr✐❜✉t✐♦♥s ❢r♦♠ t❤❡ ❝♦♥t✐♥✉✉♠ ❛♥❞BB¯❜❛❝❦❣r♦✉♥❞✱ r❡s♣❡❝t✐✈❡❧②✳

0 0.5 1 1.5 2

counts/50MeV/c

0 100 200 300

0.5 0.6 0.7 0.8 0.9 1

counts/0.02

0 100 200 300 400

❋✐❣✉r❡ ✷✳ p^∗_B❛♥❞Rs/b❞✐str✐❜✉t✐♦♥s ♦❢B❝❛♥❞✐❞❛t❡s r❡❝♦♥str✉❝t❡❞ ✇✐t❤K⁰_L✭❞❛t❛ ♣♦✐♥ts✮✳

❚❤❡ r❡❞ s♦❧✐❞ ❧✐♥❡s s❤♦✇ t❤❡ ❝♦rr❡s♣♦♥❞✐♥❣ ♦♥❡ ❞✐♠❡♥s✐♦♥❛❧ ♣r♦❥❡❝t✐♦♥s ♦❢ t❤❡ ✜tt❡❞ ♠♦❞❡❧ ✭s✐❣✲

♥❛❧✰❜❛❝❦❣r♦✉♥❞✮✳ ❚❤❡ ❜❧✉❡✱ ❣r❡❡♥✱ ❛♥❞ ②❡❧❧♦✇ ❛r❡❛s s❤♦✇ t❤❡ ❝♦♥tr✐❜✉t✐♦♥s ❢r♦♠ t❤❡ ❝♦♥s✐❞❡r❡❞

❜❛❝❦❣r♦✉♥❞ ❝❛t❡❣♦r✐❡s✿ ❢❛❦❡η^′✱ r❡❛❧η^′✇✐t❤ ❢❛❦❡K_L⁰✱ ❛♥❞ r❡❛❧η^′✇✐t❤ r❡❛❧K⁰_L✱ r❡s♣❡❝t✐✈❡❧②✳

✕ ✽ ✕

Figure 1: Projections of the fit to the data for the fit observables of η⁰K⁰

S (first three plots from the right) andη⁰K⁰

L(fourth and fifth plot).

Forη⁰K_S⁰, the total PDF is given in red, theq¯qbackground contri- bution - in yellow and theBB¯background contribution - in blue. For η⁰K⁰_L, the total PDF is in red, the combinatorial backgrounds with fake η⁰, with fakeK⁰_Land with both realη⁰andK⁰_Lare given in blue, green and yellow, respectively.

energy and the nominal K⁰_L mass. In total, we recon- struct 2503±63η⁰K_S⁰ events and 1041±41η⁰K_L⁰ sig- nal events, where the uncertainties are statistical only.

Following this, we fit the∆tdistribution for the twoB meson flavoursq to extract theCP parameters, where q= +1 orq=−1 if theBon the tag side isBor ¯B. Pro- jections of the fit to the data are shown in Fig. 2. Our preliminary results are

A_η0K⁰ = +0.03±0.05 (stat)±0.04 (syst), S_η0K⁰ = +0.68±0.07 (stat)±0.03 (syst).

The main contribution to the A_η⁰_K0 systematic uncer- tainty comes from the tag-side interference effect and for S_η⁰_K0 - from the uncertainties in the ∆t resolution function parameters. Signal enhanced projections from the fit to the data are shown in Fig. 1. The measured values of A_η⁰_K⁰ andS_η⁰_K⁰ are the world’s most precise values ofCPviolation parameters in this particular de- cay and also out of allb→sqq¯transition dominated de- cays. They are consistent with previous measurements by Belle [3] and BaBar [4] and with the SM predictions.

3. Measurement of branching fractions andCPvio- lation parameters inB→ωKdecays

We present the results from the measurements of the neutral decay mode B⁰ → ωK_S⁰ and the charged decay mode B⁻ → ωK⁻. The SM predicts 0.1 ≤ ∆S_ω0K⁰_S ≤ 0.2 [5, 6, 7, 8].

We measure the branching fractions and theCPpa- rameters of the two decay modes in a seven-dimensional

/Nuclear Physics B Proceedings Supplement 00 (2014) 1–4 3

-8 -6 -4 -2 0 2 4 6 8

Events(/1.5ps)

0 20 40 60 80 100 120

140 q=+1

q=-1

-8 -6 -4 -2 0 2 4 6 8

Asymmetry

-1 -0.5 0 0.5 1

-6 -4 -2 0 2 4 6

Events(/1.5ps)

0 5 10 15 20 25 30 35

40 q=+1

q=-1

-6 -4 -2 0 2 4 6

Asymmetry

-1 -0.5 0 0.5 1

❋✐❣✉r❡ ✸✳ ❇❛❝❦❣r♦✉♥❞ s✉❜tr❛❝t❡❞∆t❞✐str✐❜✉t✐♦♥ ✭t♦♣✮ ❛♥❞ ❛s②♠♠❡tr② ✭❜♦tt♦♠✮ ❢♦rB⁰→η^′K⁰_S

✭❧❡❢t✮ ❛♥❞B⁰→η^′K_L⁰✭r✐❣❤t✮ ❡✈❡♥ts ✇✐t❤ ❣♦♦❞ ✢❛✈♦r t❛❣s ✭r >0.5✮✳ ❆❧❧ r❡❝♦♥str✉❝t❡❞ ♠♦❞❡s ❛r❡

❝♦♠❜✐♥❡❞✳ ❚❤❡ s♦❧✐❞ ❝✉r✈❡s s❤♦✇ t❤❡ ✜tt❡❞ P❉❋✱ ❛♥❞ t❤❡ ♣♦✐♥ts ✇✐t❤ ❡rr♦r✲❜❛rs s❤♦✇ t❤❡ ❞❛t❛

❞✐str✐❜✉t✐♦♥s✳

s②st❡♠❛t✐❝ ✉♥❝❡rt❛✐♥t② ❞✉❡ t♦ t❤❡ ■P ❝♦♥str❛✐♥t ✐♥ t❤❡ ✈❡rt❡① r❡❝♦♥str✉❝t✐♦♥ ✐s ❡st✐♠❛t❡❞

❜② ✈❛r②✐♥❣ t❤❡ ■P ♣r♦✜❧❡ s✐③❡ ✐♥ t❤❡ ♣❧❛♥❡ ♣❡r♣❡♥❞✐❝✉❧❛r t♦ t❤❡z✲❛①✐s✳ ❚❤❡ ❡✛❡❝t ♦❢ t❤❡

❝r✐t❡r✐❛ ❢♦r t❤❡ s❡❧❡❝t✐♦♥ ♦❢ tr❛❝❦s ✉s❡❞ ✐♥ t❤❡Btag✈❡rt❡① r❡❝♦♥str✉❝t✐♦♥ ✐s ❡st✐♠❛t❡❞ ❜②

❝❤❛♥❣✐♥❣ t❤❡ r❡q✉✐r❡♠❡♥t ♦♥ t❤❡ ❞✐st❛♥❝❡ ♦❢ ❝❧♦s❡st ❛♣♣r♦❛❝❤ ✇✐t❤ r❡s♣❡❝t t♦ t❤❡ r❡❝♦♥✲

str✉❝t❡❞ ✈❡rt❡① ❜②±100µ♠ ❢r♦♠ t❤❡ ♥♦♠✐♥❛❧ ♠❛①✐♠✉♠ ✈❛❧✉❡ ♦❢ ✺✵✵µ♠✳ ❙♠❛❧❧ ❜✐❛s❡s ✐♥

t❤❡∆z♠❡❛s✉r❡♠❡♥t ❛r❡ ♦❜s❡r✈❡❞ ✐♥e⁺e⁻→µ⁺µ⁻❛♥❞ ♦t❤❡r ❝♦♥tr♦❧ s❛♠♣❧❡s✿ t♦ ❛❝❝♦✉♥t

❢♦r t❤❡s❡✱ ❛ s♣❡❝✐❛❧ ❝♦rr❡❝t✐♦♥ ❢✉♥❝t✐♦♥ ✐s ❛♣♣❧✐❡❞ ❛♥❞ t❤❡ ✜t ✐s r❡♣❡❛t❡❞✳ ❚♦ ❡st✐♠❛t❡ t❤❡

✉♥❝❡rt❛✐♥t② ❞✉❡ t♦ t❤❡|∆t|✜t r❛♥❣❡✱ ✇❡ ✈❛r② t❤❡ r❡q✉✐r❡♠❡♥t|∆t|<70♣s ❜②±30♣s✳ ❋♦r t❤❡ s②st❡♠❛t✐❝ ✉♥❝❡rt❛✐♥t✐❡s ❞✉❡ t♦ ❛♥ ✐♠♣❡r❢❡❝t ❙❱❉ ❛❧✐❣♥♠❡♥t ✇❡ ✉s❡ t❤❡ ✈❛❧✉❡ ❢r♦♠ t❤❡

❇❡❧❧❡ ❧❛t❡stsin 2φ₁♠❡❛s✉r❡♠❡♥t ❬✷✸❪✱ ❡st✐♠❛t❡❞ ❢r♦♠ ▼❈ s❛♠♣❧❡s ✇✐t❤ ❛rt✐✜❝✐❛❧ ♠✐s❛❧✐❣♥✲

♠❡♥t ❡✛❡❝ts✳ ❚❤❡ ♠❛❥♦r ❝♦♥tr✐❜✉t✐♦♥ t♦ t❤❡Sη^′K⁰✉♥❝❡rt❛✐♥t② ❝♦♠❡s ❢r♦♠ t❤❡ ✉♥❝❡rt❛✐♥t✐❡s

✐♥ t❤❡∆tr❡s♦❧✉t✐♦♥ ❢✉♥❝t✐♦♥ ♣❛r❛♠❡t❡rs✳ ❲❡ ✈❛r② ❡❛❝❤ ♦❢ t❤❡ ♣❛r❛♠❡t❡rs ♦❜t❛✐♥❡❞ ❢r♦♠

❞❛t❛ ✭▼❈✮ ❜②±1σ✭±2σ✮✱ r❡♣❡❛t t❤❡ ✜t✱ ❛♥❞ ❛❞❞ t❤❡ ✈❛r✐❛t✐♦♥s ✐♥ q✉❛❞r❛t✉r❡✳ ❙✐♠✐❧❛r❧②

✇❡ ❡st✐♠❛t❡ t❤❡ ❝♦♥tr✐❜✉t✐♦♥s ❢r♦♠ t❤❡ ✉♥❝❡rt❛✐♥t✐❡s ✐♥ t❤❡ ❡①tr❛❝t❡❞ s✐❣♥❛❧ ❢r❛❝t✐♦♥s✱ t❤❡

❜❛❝❦❣r♦✉♥❞∆t❞✐str✐❜✉t✐♦♥s✱ ❛♥❞ ♣❤②s✐❝s ♣❛r❛♠❡t❡rsτ_B⁰❛♥❞∆m_d✳ ❙②st❡♠❛t✐❝ ❡rr♦rs ❞✉❡

t♦ ✉♥❝❡rt❛✐♥t✐❡s ✐♥ t❤❡ ✇r♦♥❣✲t❛❣ ❢r❛❝t✐♦♥s ❛r❡ st✉❞✐❡❞ ❜② ✈❛r②✐♥❣ t❤❡ ✇r♦♥❣ t❛❣ ❢r❛❝t✐♦♥

✐♥❞✐✈✐❞✉❛❧❧② ✐♥ ❡❛❝❤rr❡❣✐♦♥✳ ❆ ♣♦ss✐❜❧❡ ✜t ❜✐❛s ✐s ❡①❛♠✐♥❡❞ ❜② ✜tt✐♥❣ ❛ ❧❛r❣❡ ♥✉♠❜❡r ♦❢

▼❈ ❡✈❡♥ts✳ ❋✐♥❛❧❧② ✇❡ ❡st✐♠❛t❡ t❤❡ ❝♦♥tr✐❜✉t✐♦♥ ❢r♦♠ t❤❡ ❡✛❡❝t ♦❢ t❤❡ t❛❣✲s✐❞❡ ✐♥t❡r❢❡r❡♥❝❡

❬✷✽❪✱ ✇❤✐❝❤ ❜r✐♥❣s ❛ s✐❣♥✐✜❝❛♥t ❝♦♥tr✐❜✉t✐♦♥ t♦ t❤❡ s②st❡♠❛t✐❝ ✉♥❝❡rt❛✐♥t② ♦❢Aη′K⁰✳ ■♥t❡r✲

❢❡r❡♥❝❡ ❜❡t✇❡❡♥ t❤❡ ❈❑▼✲❢❛✈♦r❡❞ ❛♥❞ t❤❡ ❈❑▼✲s✉♣♣r❡ss❡❞B→Dtr❛♥s✐t✐♦♥s ✐♥ t❤❡ftag

✜♥❛❧ st❛t❡ r❡s✉❧ts ✐♥ ❛ s♠❛❧❧ ❝♦rr❡❝t✐♦♥ t♦ t❤❡ P❉❋ ❢♦r t❤❡ s✐❣♥❛❧∆t❞✐str✐❜✉t✐♦♥✳ ❚❤❡ s✐③❡

♦❢ t❤❡ ❝♦rr❡❝t✐♦♥ ✐s ❡st✐♠❛t❡❞ ✉s✐♥❣ t❤❡B⁰→D^∗−l⁺νs❛♠♣❧❡✳ ❚❤❡♥ ❛ s❡t ♦❢ ▼❈ ♣s❡✉❞♦✲

❡①♣❡r✐♠❡♥ts ✐s ❣❡♥❡r❛t❡❞ ❛♥❞ ❛♥ ❡♥s❡♠❜❧❡ t❡st ✐s ♣❡r❢♦r♠❡❞ t♦ ♦❜t❛✐♥ ♣♦ss✐❜❧❡ s②st❡♠❛t✐❝

❜✐❛s❡s ✐♥Sη^′K⁰❛♥❞Aη^′K⁰✳

✕ ✶✶ ✕

Figure 2: Projections of the data fit to the∆tdistribution forη⁰K_S⁰ (left) andη⁰K_L⁰(right).

unbinned maximum likelihood fit toMbc,∆E, the mass m3πand helicity angleH_3πof theωcandidates, a Fisher discriminantF_{BB/q¯¯ q}, ∆tand the Bflavour q. The t is performed simultaneously to the neutral and charged modes, sharing common calibration factors. Following that, the shapes of the fit observables are fixed and the A_CPparameter is obtained from two further fits to ex- tract the number ofB⁺andB⁻events. Projections of the the fit to the data are shown in Fig. 3. We obtain

B_B0→ωK⁰ =(4.5±0.4 (stat)±0.3 (syst))×10⁻⁶, B_B−→ωK⁻ =(6.8±0.4 (stat)±0.4 (syst))×10⁻⁶,

A_ωK0

S =−0.36±0.19 (stat)±0.05 (syst), S_ωK0

S = +0.91±0.32 (stat)±0.05 (syst), A_ωK⁻ =−0.03±0.04 (stat)±0.01 (syst).

For the branching fractions, the main contribution to the systematic uncertainties is theπ⁰reconstruction effi- ciency. ForA_ωK0

S, the dominant systematic effect is the tag-side interference and for S_ωK0

S andA_ωK− - the∆t resolution function. By performing a likelihood scan in theA_CP− S_CPplane, we find a deviation of 3.1σfrom theCPconservation hypothesis, which makes this result the first evidence forCPviolation in theB⁰→ωK_S⁰de- cay mode. Apart from theS_ωK0

S result, this is the most precise measurement of theB→ωKdecay modes. The results are mostly in agreement with the previous mea- surements of Belle [9, 10] and BaBar [11, 12]. The analysis has been published in the July 2014 issue of Physical Review D [13].

4. Conclusion

The results from the measurements onb → sqq¯de- cays presented in these proceedings are consistent with the SM predictions and with the current world average

]2Events / [0.0025 GeV/c 5

10 15 20 25

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-2 0 2

Events / [0.0125 GeV]

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q /q B FB

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-2 0 2

]2Events / [0.005 GeV/c

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2] [GeV/c 3π M 0.73 0.75 0.77 0.79 0.81 0.83

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-2 0 2

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total PDF signal

q q

B B

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-2 0 2

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50 q = +1

q = -1

t [ps]

∆ -7.5 -5 -2.5 0 2.5 5 7.5

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0B-N0BN -0.5

0 0.5

Figure 3: Projections of the data fit to theB⁰→ωK⁰_Sobservables.

on sin 2φ1 measured inb → c¯cstransitions [14]. The uncertainties on the parameter are still very large and so for new physics to be observed in these decay modes, more data is needed. This will be provided in the future by the Belle II and the LHCb experiments.

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