衰落的证据BS0→K∗0μ+μ−$${B}_S^0\至{\overline{K}}^{\ast0}{\mu}^{+}{\mu}^{-}$$资源-CSDN文库

Open

Access

66 浏览量 2020-04-09 06:10:45 上传评论收藏 1.8MB PDF 举报

资源推荐

资源详情

资源评论

JHEP07(2018)020

Published for SISSA by Springer

Received: April 20, 2018

Revised: June 12, 2018

Accepted: June 19, 2018

Published: July 3, 2018

Evidence for the decay B

→ K

∗0

−

The LHCb collaboration

E-mail: andrew.christopher.crocombe@cern.ch

Abstract: A search for the decay B

→ K

∗0

−

is presented using data sets corre-

sponding to 1.0, 2.0 and 1.6 fb

−1

of integrated luminosity collected during pp collisions

with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, respectively. An

excess is found over the background-only hypothesis with a signiﬁcance of 3.4 standard

deviations. The branching fraction of the B

→ K

∗0

−

decay is determined to be

B(B

→ K

∗0

−

) = [2.9 ±1.0 (stat) ±0.2 (syst) ±0.3 (norm)] ×10

−8

, where the ﬁrst and

second uncertainties are statistical and systematic, respectively. The third uncertainty is

due to limited knowledge of external parameters used to normalise the branching fraction

measurement.

Keywords: B physics, FCNC Interaction, Flavor physics, Hadron-Hadron scattering (ex-

periments), Rare decay

ArXiv ePrint: 1804.07167

Open Access, Copyright CERN,

for the beneﬁt of the LHCb Collaboration.

Article funded by SCOAP

https://doi.org/10.1007/JHEP07(2018)020

JHEP07(2018)020

decay appears to be systematically lower than current SM predictions. Global analyses

of b → s processes favour a modiﬁcation of the SM at the level of 4 to 5 standard devia-

tions [20–24]. Similar studies of b → d processes are important to understand the ﬂavour

structure of the underlying theory.

This paper presents a search for the decay B

→ K

∗0

−

, where the inclusion of

charge-conjugate processes is implied throughout, using data collected with the LHCb

experiment in pp collisions during Runs 1 and 2 of the LHC. The data set used in this

paper is as follows: 1.0 fb

−1

of integrated luminosity collected at a centre-of-mass energy of

7 TeV during Run 1; 2.0 fb

−1

of integrated luminosity collected at a centre-of-mass energy

of 8 TeV during Run 1; and 1.6 fb

−1

of integrated luminosity collected at a centre-of-mass

energy of 13 TeV during Run 2. Section 2 of this paper describes the LHCb detector and

the experimental setup used for the analysis. Section 3 outlines the selection processes

used to identify signal candidates. Section 4 describes the method used to estimate the

number of B

→ K

∗0

−

decays in the data set. Section 5 describes the determination of

the B

→ K

∗0

−

branching fraction, normalising the number of observed signal decays

to the number of B

→ J/ψ K

∗0

decays present in the data set. Section 6 discusses sources

of systematic uncertainty on the B

→ K

∗0

−

branching fraction. Finally, conclusions

are presented in section 7.

2 Detector and simulation

The LHCb detector [25, 26] is a single-arm forward spectrometer covering the

pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c

quarks. The detector includes a high-precision tracking system consisting of a silicon-

strip vertex detector surrounding the pp interaction region [27], a large-area silicon-strip

detector located upstream of a dipole magnet with a bending power of about 4 Tm, and

three stations of silicon-strip detectors and straw drift tubes [28] placed downstream of

the magnet. The tracking system provides a measurement of momentum, p, of charged

particles with a relative uncertainty that varies from 0.5% at low momentum to 1.0% at

200 GeV/c. The minimum distance of a track to a primary vertex (PV), the impact param-

eter (IP), is measured with a resolution of (15 + 29/p

) µm, where p

is the component of

the momentum transverse to the beam, in GeV/c. Diﬀerent types of charged hadrons are

distinguished using information from two ring-imaging Cherenkov detectors [29]. Photons,

electrons and hadrons are identiﬁed by a calorimeter system consisting of scintillating-

pad and preshower detectors, an electromagnetic calorimeter and a hadronic calorimeter.

Muons are identiﬁed by a system composed of alternating layers of iron and multiwire

proportional chambers [30].

The online event selection is performed by a trigger [31]. The trigger consists of a

hardware stage, based on information from the calorimeter and muon systems, followed

by a software stage, which applies a full event reconstruction. The signal candidates are

required to pass through a hardware trigger that selects events containing at least one

muon with p

greater than 1 to 2 GeV/c, depending on the data-taking conditions. The

software trigger requires a two-, three- or four-track secondary vertex with a signiﬁcant

– 2 –

JHEP07(2018)020

displacement from any primary pp interaction vertex. At least one charged particle must

have a large transverse momentum p

> 1 GeV/c and be inconsistent with originating from

a PV. A multivariate algorithm [32] is used for the identiﬁcation of secondary vertices

consistent with the decay of a b hadron.

Samples of simulated B

→ K

∗0

−

, B

→ K

∗0

−

, B

→ J/ψ K

∗0

and

→ J/ψ K

∗0

decays are used to develop an oﬄine event selection and to determine the

eﬃciency to reconstruct the B

and B

candidates in the diﬀerent data-taking periods.

In the simulation, pp collisions are generated using Pythia [33] with a speciﬁc LHCb

conﬁguration [34]. Decays of hadronic particles are described by EvtGen [35], in which

ﬁnal-state radiation is generated using Photos [36]. The interaction of the generated parti-

cles with the detector, and its response, are implemented using the Geant4 toolkit [37, 38]

as described in ref. [39]. Data-driven corrections are applied to the simulation to account

for mismodelling of the detector occupancy and of the B

(s)

meson production kinemat-

ics. The particle identiﬁcation (PID) performance is measured from data using calibration

samples [26].

3 Candidate selection

Signal candidates are formed by combining a K

∗0

candidate with two oppositely charged

tracks, which are identiﬁed as muons by the muon system. The K

∗0

meson is reconstructed

through its decay to the K

−

ﬁnal state with invariant mass within ±70 MeV/c

of the

known K

∗

(892)

mass [40]. The muon pair is required to have an invariant mass squared

in the range 0.1 < q

< 19.0 GeV

, excluding the region 12.5 < q

< 15.0 GeV

dominated by the ψ(2S) resonance. Candidates in the region 8.0 < q

< 11.0 GeV

which are dominated by decays via a J/ψ resonance, are treated separately in the analysis.

The remaining candidates include B

meson decays that produce a dimuon pair through the

decay of a light-quark resonance or a charmonium state above the open charm threshold,

which are inseparable from the short-distance component of the decay. These are considered

part of the signal in the analysis.

The selection process used in this analysis is similar to that described in ref. [18]. The

four charged tracks are required to each have a signiﬁcant IP with respect to all PVs in

the event and to be consistent with originating from a common vertex. The B

(s)

meson

candidate is required to be consistent with originating from one of the PVs in the event

and its decay vertex is required to be well separated from that PV. The kaon and pion

candidates must also be identiﬁed as kaon-like and pion-like by a multivariate algorithm [26]

based on information from the RICH detectors, tracking system and calorimeters. The PID

requirements are chosen to maximise the sensitivity to a SM-like B

→ K

∗0

−

signal.

To improve the resolution on the reconstructed K

−

invariant mass,

m(K

−

), candidates with an uncertainty larger than 22 MeV/c

on their measured

mass are rejected. The opening angle between every pair of ﬁnal-state particles is also

required to be larger than 5 mrad in the detector. This requirement removes a possible

source of background that arises when the hits associated to a given charged particle are

mistakenly used in more than one reconstructed track. A kinematic ﬁt is also performed,

– 3 –

剩余23页未读，继续阅读

评论收藏

内容反馈

weixin_38731226

粉丝: 6
资源: 926

衰落的证据BS0→K ∗0μ+ μ− $$ {B} _S ^ 0 \至{\ overline {K}} ^ {\ ast 0} ...

最新资源

衰落的证据BS0→K ∗0μ+ μ− $$ {B} _S ^ 0 \至{\ overline {K}} ^ {\ ast 0} ...

B s 0→K ∗ 0 K ∗ 0 $$ {B} _ {{s}} ^ 0 \至{K} ^ {\ ast 0} {\ overline {K}} ^ {\ ast的幅度分析 0} $$衰变并测量B的分支分数0→K ∗ 0 K ∗ 0 $$ {B} ^ 0 \至{K} ^ {\ ast 0} {\ overline {K}} ^ { \ ast 0} $$衰减

稀有衰变Λb→Λ1520→NK + + − $$ {\ Lambda} _b \ to \ Lambda（1520）\ left（\ to N \ overline {K} \ right）{\ ell} ^ {+} {\ ell} ^ {-} $$

在Λb 0→Λc +μ− v¯μ$$ {\ varLambda} _b ^ 0 \至{\ varLambda} _c ^ {+} {\ mu} ^ {-} {\ overline { v}} _ {\ mu} $$衰减

B \ X s + + − $$ \ overline {B} \至{X} _s {\ ell} ^ {+} {\ ell} ^ {-} $$的次导功率因式分解

观察衰减B¯s0→χc2K+ K− $$ {\ overline {B}} _ s ^ 0 \至{\ chi} _ {c2} {K} ^ {+} {K} ^ {-} $$ 在ϕ区域

B中的CP违反0→D ∗ +μ-νμμ$$ {\ overline {B}} ^ 0 \至{D} ^ {\ ast +} {\ mu} ^ {-} {\ overline {\ nu}} _ {\ mu} $$

两体无魅力重子衰变的证据B +→p ^ $$ {B} ^ {+} \到p \ overline {\ varLambda} $$

B s 0和B s 0中的共振和CP违反→J /ψK + K − $$ {\ overline {B}} _ s ^ 0 \ to J / \ psi {K} ^ {+} {K} ^ {-} $$在above上方的质量区域中衰减（1020）

用B±→D（K S 0 $$ {K} _ {\ mathrm {S}} ^ 0 $$π+π-π0）对KKM角ϕ 3的首次测量

K +→μ+νμννν$$ {\ mathrm {K}} ^ {+} \ to {\ mu} ^ {+} {\ nu} _ {\ mu} \ nu \ overline {\ nu} $$和K +→e +νeνν¯$$ {\ mathrm {K}} ^ {+} \ to {\ mathrm {e}} ^ {+} {\ nu} _ {\ mathrm {e} } \ nu \ overline {\ nu} $$在手征扰动理论中衰减

B \→D ∗τν$$ $$ \ overline {B} \ to {D} ^ {\ left（\ ast \ right）} \ tau \ overline {\ nu} $$受B限制的ALRSM中过剩，D衰减 和D 0 − D¯0 $$ {D} ^ 0-{\ overline {D}} ^ 0 $$混合

在B s 0→ϕϕ $$ {B} _s ^ 0 \至\ phi \ phi $$衰减中测量CP违规，并搜索B 0→ϕϕ衰减

将b→s $$ $$ b \连接到sell \ overline {\ ell} $$异常与增强的稀有非轻子B的0 $$ {\ overline {B}} _ s ^ 0 $$在Z上衰减 模型

对于B s-B s $$ {B} _s-{\ overline {B}} _ s $$系统中的宽度差，其对对数精度的倒数第二个：费米子对有序的贡献（mc / mb）0和（mc / mb）1

B0→D0D0的CP不对称度C 00的预测$$ {B} ^ 0 \至{D} ^ 0 \ overline {D ^ 0} $$衰减

B s 0→（K +π-）（K-π+）衰变中违反CP的相位ϕsdd′$$ {\ phi} _s ^ {d \ overline {d}} $$的首次测量

来自固定目标实验SHiP的ντ中微子和ντ$$ {\ overline {\ nu}} _ {\ tau} $$反中微子的产生不对称性

如何将B d 0→J /ψπη，K K $$ {\ overline {B}} _ d ^ 0 \应用于J / \ psi \ left（\ uppi \ eta，\ overline {K} K \ 右）$$衰减以提取有关πη散射的信息

在RK ∗ $$ {R_K} _ {{} ^ {\ left（\ ast \ right）}} $$异常的瘦夸克模型中测试最小的风味违规

对LHCb处的衰变B s 0→K S 0 K ∗（892）0的首次观测

RD *，RK * $$ {R} _ {D ^ {\ left（* \ right）}}，{R} _ {K ^ {\ left（* \ right）}} $$和2HDM中的中微子质量 -III与右手中微子

在s = 8 $$ \ sqrt {s} =的pp碰撞中，测量tt W $$ t \ overline {t} W $$和tt z $$ t \ overline {t} Z $$生产横截面。 带有ATLAS探测器的8 $$ TeV

Z 2对称和对齐类型的两个希格斯双峰模型的风味约束

利用B s 0，χc0和D 0共振以及弱an灭非共振拓扑研究B c +衰减至K + K-π+最终状态

D *极化与R D ∗ $$ {R} _ {D ^ {\ left（\ ast \ right）}} $$异常在quar夸克模型中

最新资源

B \→D ∗τν$$ $$ \ overline {B} \ to {D} ^ {\ left（\ ast \ right）} \ tau \ overline {\ nu} $$受B限制的ALRSM中过剩，D衰减和D 0 − D¯0 $$ {D} ^ 0-{\ overline {D}} ^ 0 $$混合

将b→s $$ $$ b \连接到sell \ overline {\ ell} $$异常与增强的稀有非轻子B的0 $$ {\ overline {B}} _ s ^ 0 $$在Z上衰减模型

RD ，RK $$ {R} _ {D ^ {\ left（* \ right）}}，{R} _ {K ^ {\ left（* \ right）}} $$和2HDM中的中微子质量 -III与右手中微子

在s = 8 $$ \ sqrt {s} =的pp碰撞中，测量tt W $$ t \ overline {t} W $$和tt z $$ t \ overline {t} Z $$生产横截面。带有ATLAS探测器的8 $$ TeV