Search for the 0"" Glueball in Υ(1S, 2S) decays

Sen JiaBeihang University & KEK

(on behalf of the Belle&BelleII Collaboration)

INTERNATIONAL SCHOOL OF SUBNUCLEAR PHYSICS56th Course: From gravitational waves to QED, QFD and QCD

OutlinelKEKB and Belle Detector

lBelle2 experiment

lMotivation

lCommon selection criteria

lThe measurements of bottomonium inclusive

decays

lSearch for G0−−

lConslusion

S. Jia, EMFCSC 2018 -2-

KEKB and Belle Detector

KEK, Tsukuba, Japan

8 × 3.5 GeV22 mrad crossing

1999-20101014/fb

The KEKB Collider

World record:

L=2.1×1034/cm2/sec

S. Jia, EMFCSC 2018 -3-

Belle II Experiment

l Nano-beam design (by P. Raimondi for SuperB)

l Double beam currentsl Squeezes beam @IP by 1/20l Target luminosity is 𝓛 =𝟖×𝟏𝟎𝟑𝟓 cm-2s-1 (×40 w.r.t. BELLE)

A hadronic event recorded at 00:38, 26.04.2018the first collision comfirmation

Expected Dataset at Belle2

S. Jia, EMFCSC 2018 -4-

7.0 𝒆" × 4.0 𝒆3 GeV

Motivation

lQCD allows the existences of glueballs.

l There are no definite conclusions from experimental results. One of the reasons is its mixing with quarkonium states.

l The 0-- glueballs are inaccessible by the quarkonium states and their quantum numbers enable their productions in the decays of vector quarkonium easier.

l Search for 0-- glueballs in proposed production channel:Υ(1S,2S) →χ78+ G0

--, Υ(1S,2S) → f1(1285)+ G0--，χ98 → J/ψ+ G0

--,and χ98 →ω+ G0

--. The predicted glueballs masses are 2.80, 3.81 and 4.33GeV/c2.[PRL113, 221601 (2014)]、[JHEP 1510 (2015) 137]

-5-S. Jia, EMFCSC 2018

Data Sample

-6-

2.12E+07 0

1.02E+08

9.32E+06

9.86E+07

1.58E+08

0.00E+00

5.00E+07

1.00E+08

1.50E+08

2.00E+08

1 2 3

Data sample events of Y(1S) and Y(2S) Y(1S) Y(2S)

BABARCLEO BELLE

Belle experiment has collected the largest data samples of Υ(1S,2S) in the world !Analysis Strategy:

In the channels mentioned above, we search for the G0-- signals in the recoil

mass spectra of the χ78, f1(1285), J/ψ, and ω with G0-- widths varying from 0.0

to 0.5 GeV in steps of 0.05 GeV.

S. Jia, EMFCSC 2018

Common selections

S. Jia, EMFCSC 2018 -7-

l |dr| < 0.5cm, |dz| < 4cm and PT<0.1lGood photon candidates, Eγ>50MeV and not match the

extrapolation of any charged tracklNtrack > 4lReconstruct J/ψ, both Re >0.95; one Rµ>0.95 and the other

Rµ>0.05 l For pions, RK<0.4l For J/ψ, η and πA candidates, a mass constraint fit is used.

𝑅C =DE

DE3DFGFHE𝑅I =

DJDJ3DK3DL

𝑅M =DK

DK3DL

Window cuts:J/ψ: |𝑀OPOH-𝑚J/R|<0.03GeV/c2

χ78: 0.36 < 𝐸T∗ < 0.41f1(1285): 1.23<𝑀(𝜂𝜋3𝜋")<1.33GeV/c2

𝜔: 0.755<M(𝜋3𝜋"𝜋A)<0.805GeV/c2

χ78(1P) in Υ(1S, 2S) inclusive decays

l Partition the data samples according to the scaled momentum to correct the efficiency

𝑥 =𝑝[\]∗

12 𝑠� ×(𝑠 − 𝑚[\]

a )

Mode 𝑩𝑹(×10"d) Comments

Υ(1S) ⟶𝜒𝑐1 + 𝑎𝑛𝑦𝑡ℎ𝑖𝑛𝑔 1.90± 0.43± 0.14 with an improved precision

Υ(2S) ⟶𝜒𝑐1 + 𝑎𝑛𝑦𝑡ℎ𝑖𝑛𝑔 2.24± 0.44± 0.20 for the first time

The differential BR

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lClear f1(1285) signal in ϒ(1S,2S) inclusive decays

l J/ψ production in χ9q (J = 0, 1, 2) decays

Υ 1S, 2S →f1(1285)+X and χ9q → J/ψ+X

Mode 𝑩𝑹(×10"d)

Υ(1S) ⟶ f1(1285)+ anything 46± 28± 13

Υ(2S) ⟶ f1(1285)+ anything 22± 15± 6.3

Mode 𝑩𝑹(×10"y)

𝜒za ⟶ J/ψ + anything 1.5± 0.34± 0.22

𝜒z8 ⟶ J/ψ + anything 1.1 at 90% C.L.

𝜒zA ⟶ J/ψ + anything 2.3 at 90% C.L.

3.5σ

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The χ78 recoil mass spectra in the (a) Υ(1S) and (b) Υ(2S) data samples.

Measurements of Υ(1S,2S) →χ78/f1(1285) + G0--

The f1(1285) recoil mass spectra in the (a) Υ(1S) and (b) Υ(2S) data samples.

Mode Upper Limits at 90% C.L. Mode Upper Limits at 90% C.L.

Υ(1S,2S) ⟶ χ78 + G 10−5 Υ(1S,2S) ⟶ f1(1285) +G 10-4 -10-

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Measurements of χ98 → J/ψ(ω) + G0−−

Mode Upper Limits at 90% C.L. Mode Upper Limits at 90% C.L.

χ98→J/ψ+G 10−4 χ98→ω+G 10-3

The χ98 is identified through the decay Υ(2S) → γ𝜒z8 .

The γJ/ψ recoil mass spectra in the Υ(2S) data samples.

The γω recoil mass spectra in the Υ(2S) data samples.

S. Jia, EMFCSC 2018

Ø We have searched for the 0−− glueball in ϒ(1S), ϒ(2S), and χ78decays for the first time.

Ø No evident signal is found at three theoretically predicted masses in the processes and 90% C.L. upper limits are set on the branching fractions.

Ø Distinct χ78 and f1(1285) signals are observed in the ϒ(1S) and ϒ(2S) inclusive decays.

Ø The evidence of χ9a → J/ψ+anything

Ø More opportunity in Belle II Experiment.

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Conclusion

More opportunities

PRD 95, 012001 (2017)PRD 96, 112002 (2017)

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