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Study of B0 →X(3872) K+ π-

Anu Bala

Jan 19, 2012

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Motivation

⧫ X(3872) not a conventional charmonium state

⧫ Study of B X3872 K π (by K. Trabelsi, BN 999) B X3872 K π signal, K* resonance has less

signal as compared to K π. Not compatible with: what is observed in

other charmonium decays like ψ' K+ π-.

⧫ Important to understand X(3872) nature and valuable for theoretical understanding of X(3872).

⧫ At present update/cross-check X(3872) K+ π- , later perform same study for the neutral decays.

Many thanks to Karim for giving this analysis as my Ph.D. topic.

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Introduction

Era of the new family of particles, named XYZ, started from the observation of X(3872) in the J/ψ π+π- final state by the Belle experimentMany new states have been found/observed/studied by Belle and other experiments, BaBar, CDF, D0, CLEO, CMS, LHC-b after that This is just a short list of them X(3872), X(3940), Y(3940), X(4160), Y(4008), Y(4260), Y(4350), Y(4660), Z(3930), Z(4415), Z(4430)+, Yb(10580), …These particles are not fittable to any of the known or predicted statesAngular analysis by CDF & Belle suggest its JPC to be 1++ or 2-+

Most probably it is new type of quark particles in addition to mesons and baryon, although it is not proved yet

Observation of X(3872)

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X(3872)Ψ '

M(π+π-l+l-)- M(l+l-) It did not fit to any known cc-bar statesMass of X(3872) is close to DD*

What is it: charmonium, DD*-molecule, tetraquark...?

Observed by Belle in B± → K± π+π-J/ψ 2003

Belle data: 152 M BB eventsMass = 3872.0±0.6±0.5 MeV/c2

Significance = 10 σNew Prediction of mass: Mass=3871.46±0.37±0.07 Mev/c2

152M BB, PRL91, 262001(2003)152M BB, PRL91, 262001(2003)

Charmonium spectrum

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Selection criteria for X(3872) & Psi'B daughters selection:

charged particle selection: |dr|<1.0 cm & |dz|<2.8 cm Kid >0.6 πid>0.6 Pion of J/ψππ : πid>0.4 J/ψ reconstruction is done from leptonic mode Selection: 2.95 GeV/c2 < Me+e- <3.13 GeV/c2

: 3.02 GeV/c2 < Mμ+μ- <3.13GeV/c2

Mass constraint & vertex fit is applied. Bremsstrahlung photons within < 0.05 rad Momentum of J/ψ <1.8 GeV/c Mbc>5.27 GeV/c2 & |ΔE| <0.04 GeV Mπ+π- > 0.575 GeV/c2 & Mπ+π- > 0.389 GeV/c2

Will optimize ΔE cut500,000 events are generated for signal MC

Standard charmonium criteria used

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Reconstruction of J/ψ

J/ψ →μ+μ- J/ψ →e+e-

Mμμ GeV/c2

↓ ↓ ↓ ↓ Mee GeV/c2

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MKπ GeV/c2

BBψψ' K+ π-' K+ π-Bψ' K*0

BX(3872) K+ π-

MKπ distribution

BX(3872) K*0

MKπ GeV/c2

MKπ GeV/c2 MKπ GeV/c2

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Best Candidate Selection

*Estimated by performing fit to MJψππ

Decay Channel Multiplicity (%)

Reconstruction Efficiency* (%) Based on ΔE

Reconstruction efficiency* (%)Based on Mbc

B ψ' K+ π- 41.5 16.8 15.3

B ψ' K*(892) 40.4 16.1 14.9

B X(3872) K+π- 38.0 13.5 12.4

B X(3872) K*(892) 36.1 12.7 13.6

Tried selecting best candidate on basis of ΔE closest to 0 and Mbc closest to B nominal mass

10Typical uncertainty on eff. , order of ~ 0.06%

Signal MC MJ/ψππ distribution

BBψψ' K+ ' K+ π-π-

Bψ' K*0

BX(3872) K+ π-

BX(3872) K*0

Eff= 16.1% Eff= 16.8%

Eff= 12.7%Eff= 13.5%

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Background study for B0→ψ' K π based upon BCS: Mbc

In order to study background, we use J/ψ inclusive MC (100 times data).

The background is expected to come from Bψ' K*(892) and B+ψ' K+π-π+.

Rest of the background is almost flat and can be taken care by 1st order polynomial while fitting

MJ/ψππ GeV/c2

Background study for B0→ψ' K π based upon BCS:ΔE

MJ/ψππ GeV/c2

K π mass distribution based upon BCS: Mbc

MKπ GeV/c2

B0→J/ψππ K*0 need to be handle with care in MKπ

K π mass distribution based upon BCS:ΔE

MKπ GeV/c2

B0→J/ψππ K*0 need to be handle with care in MKπ

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Background study for X(3872) K π

MJ/ψππ GeV/c2

No serious background structure in X(3872) region.

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Background study for X(3872) K based upon ΔE

MJ/ψππ GeV/c2

No serious background structure in X(3872) region.

K π mass distribution based upon BCS: Mbc

MKπ GeV/c2

B0→J/ψππ K*0 need to be handle with care in MKπ

K π mass distribution based upon BCS:ΔE

MKπ GeV/c2

B0→J/ψππ K*0 need to be handle with care in MKπ

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Comparison with previous belle results

B → X(3872)K+π-

Efficiency (%)

BN999 8.9%

Results 13.5%

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Summaryi) Preliminary selection cuts and criteria has been done for B (J/ψππ) Kπ study.

ii) Signal generation has been done.

iii) Efficiency estimated by performing fit to MJ/ψππ.

iv) Background study is also done using J/ψ Inclusive MC.

v) Studying the background in ΔE and Mbc, revisiting BCS on the basis of background.

vi) No serious backgrounds but peaking background in MKπ needed to be handle with care.

vii) Strategy to extract signal yield will be developed.

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BACKUP

BN 999

BN 999

BN 999

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Psikpi Mbc rec eff: 15.369%

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Psikstar Mbc rec eff : 14.87%

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Xkpi Mbc rec eff: 12.45%

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Xkstar Mbc rec eff: 13.6%

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Belle

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KL

The Belle Detector

SVD - Precise location of decay vertex• Electron/”hole” pairs generated

CDC - Particle tracks, momentum• Ionize gas, ions go to wires in cells, fit track

ACC - diff between K/π via Cerenkov• Designed for 1.2-3.5GeV(threshold)

TOF - PID• Scintillation, event time and pulse shape

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The Belle Detector

ECL - Electron/photon measurements• CsI crystal. Pair production, Bremsstrahlung

KLM -KL/Muon differentiation• Resistive plate chamber, iron for KL interaction

EFC - extension of ECL• BGO

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-- definitionsgood charged track:(this depends on evtcls default) Pt >= 0.1 GeV/c helix |dr|<2cm, |dz|<5cmgood ECL cluster: E(ECL cluster) > 0.1 GeVgood Gamma: E(ECL) > 0.1 GeVErec = Sum of Pcm(good charged track) in c.m.s. + SumSelection criteriaThe following list shows the curernt selection criteria for the tau skim. -- definitionsgood charged track:(this depends on evtcls default) Pt >= 0.1 GeV/c helix |dr|<2cm, |dz|<5cmgood ECL cluster: E(ECL cluster) > 0.1 GeVgood Gamma: E(ECL) > 0.1 GeVErec = Sum of Pcm(good charged track) in c.m.s. + Sum of Egamma in c.m.s.Ptmax : maximum Pt(good charged track)Etot = Erec + |Pmiss_CM|N_barrel: No. of track with 30< theta <130 degree (barrel region)E_ECL_trk = Sum of E(ECL) in c.m.s - Sum of Egamma in c.m.s.

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--- selection criteria1. 2<= No. of good track <=82. |charge sum|<=25. Ptmax > 0.5 GeV/c6m. Event vertex |r|<1cm,|z|<3cm7. for 2 track event 7-2m. Sum of E(ECL) < 11 GeV 7-3. 5 < theta(missing momentum) < 175 degree8. Erec > 3 GeV .or. Ptmax > 1.0 GeV/c9. for 2-4 charged track case 9-1m. Etot < 9 GeV .or. maximum opening angle < 175 degree .or. 2 < Sum of E(ECL) < 10 GeV 9-2. N_barrel >= 2 .or. E_ECL_trk < 5.3 GeV

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Delte E & Mbc window

color & cabbibo

Model used

color in fitting

compete channel

j/psi MC based on mbcS