Recent results on light hadron Recent results on light hadron spectroscopy at BESspectroscopy at BES

Hongxun Yang(for BES Collaboration)

Moriond QCD and High Energy InteractionsMarch 13-20 2010

Outline

Introduction of BES at BEPCIntroduction of BES at BEPC analysis of charged analysis of charged at BESII at BESII Confirmation of ppbar mass Confirmation of ppbar mass

threshold structure at BESIIIthreshold structure at BESIIIConfirmation of X(1835) at BESIIIConfirmation of X(1835) at BESIII SummarySummary

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Beijing Electron Positron Collider (BEPC) at IHEP

Beijing Spectrometer I : 1989 -1998

BESII: 1999 -2004 L ~ 5*1030cm-2s-1@ J/ Ebeam~ 1-2.5 GeV

BESIII: 2008 (Physics run from March 2009)- ,

L~3.2*1032cm-2s-1@(3770)~30% of designed value

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Milestones of BESIII

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Observation of charged at BESII was first found in K scattering data

However, its phase shift is much less than 180o and it cannot be filled into any nonets of ordinary mesons. There have been hot debates on the existence of .

In recent years: FNAL E791 found evidence of neutral in D+ K-++. CLEO D0 K-+0 data find no evidence of . FOCUS data on D+K-++ require K*0 interfere with either a constant amplitude or a broad 0+ resonance in K. BESII observed neutral in J/ K*0K KK in 2006.

neutral pole:

qq

24872

8173 MeV/c )45309()30841(

2

iim

22 MeV/c 8743410 ,MeV/c 4319797 M

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• CLEO reported the necessity of in .

• However, no charged is needed in BABAR data.

• BESII studied charged in

0 K00 KKD

The existence of charged is expected !

0*/ KKKJ s

M(K0) GeV/c2

BESII Preliminary

K*(1410), K*(1430)

BESII Preliminary

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Partial wave analysis results

BESII Preliminary

BESII Preliminary

BESII PreliminaryBESII Preliminary

M(K) (GeV/c2)

M(K*(892)K) (GeV/c2)

M(K*(892)) (GeV/c2)

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Resonance parameters of charged

For reference, resonance parameters of neutral

Different parameterizations of give consistent results on the pole of charged . The pole position for charged is consistent with that for neutral within the error.

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arXiv:1002.0893 [hep-ex]

Observation of an anomalous enhancement X(1860) near the threshold of pp mass spectrum

Mpp-2mp (GeV)0 0.1 0.2 0.3

pp

J / pp

BESII

theoretical speculation: bound state (baryonium)

FSI effects

……

pp

PRL 91, 02201 (2003)

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No significant narrow strong enhancement near threshold(~2 if fitted with X(1860))

Mpp (GeV/c2)

The narrow threshold enhancement is NOT observed in those channels

(1S) pp@CLEO

(2 ) @S pp BESII

J / pp@BESIIPR D73, 032001 (2006)

PRL 99, 011802 (2007)

EPJ C53 ,15 (2008)

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/ , / @ BESIIIJ J pp

Observation of an anomalous enhancement near the threshold of mass spectrum at BES

IIICPC(HEP & NP), 2010, 34(4): 421-426

pp

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Fitted with a S-wave BW, M=1861+6-13 (stat)+7

-26 (syst) MeV/c2

< 38 MeV/c2 (90% CL)

BESIII preliminaryBESIII preliminary

This narrow threshold enhancement is “NOT” observed in at BESIII

No significant narrow strong enhancement near thresholdPure FSI interpretation disfavored

' @BESIIIpp

' pp

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Observation of X(1835) J/’+- at BESII

14

PRL 95,262001(2005)

Statistical Significance ~6 Statistical Significance ~5.1

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To be confirmed with ~220M J/To be confirmed with ~220M J/ data at BESIII data at BESIII

Mass spectrum of ’+- in J/’+-, ’

Significant peak at M~1835MeV

Statistic significance of X(1835) is about 18σ

BESIII preliminaryBESIII preliminary

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Mass spectrum of ’+-

in J/’+-, ’+-

Significant peak at M~1835MeV

Statistic significance of X(1835) is about 9σ

BESIII preliminary

BESIII preliminary

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17

BESII  result(Statisticsignificance ~ 7.7 ) :

M  1833.7 6.1(stat) 2.7(syst)MeV

67.7 20.3(stat) 7.7(syst)MeV

Fit result(Statisticsignificance~21 ) :

M 1842.4 2.8(stat)MeV

99.2 9.2(stat)MeV

BESIII preliminary

???Structures at higher mass region???

BESII

Combined mass spectrum of the two decay modes

X(1835) is confirmed in BESIII and the significance increases as statistics increases

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SummarySummary

BEPCII/BESIII is a major upgrade of the BESII experiment at the BEPC accelerator for studies of hadron spectroscopy and -charm physics.

BESIII has been in operation since 2008: ~110M ’ and ~220M J/ events have been collected

Recent results at on light hadron BES are presented: Partial wave analysis of charged at BESII Confirmation of ppbar mass threshold structure at BESIII Confirmation of X(1835) at BESIII

More Exciting results are expected.

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THANK YOU!THANK YOU!

Data Accumulated @ BESIII

Pb-

1

Pb-

1

Pb-

1

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In transition region between pQCD and non-pQCD.

A unique e+e- machine in the -charm energyTau charm physics with BEPCII/BESIII:

21

The Y’s are here!

From PDG

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Physics potential at BESIII

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The physics window is precision charm physics and the search for new physics.

High statistics: high luminosity machine + high quality detector. Small systematic error: high quality detector.

BEPCII: a high luminosity double–ring collider

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Achieved Luminosity

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Detector Performance and Calibration

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