Radiative Decay at BESII

' Radiative Decay at BESII

March 24, 2006

University of Toronto

Lianliang [email protected]

mailto:[email protected]

March 24, 2006 2Lianliang Ma

B. Sc. 1995.9 --- 1999.7 Shandong University, Jinan, Shandong, China First prize scholarship every year

Ph. D. 1999.9 --- 2002.4 Shandong University, Jinan, Shandong, China Work on detector simulation with Geant4: (a) Study the performance o

f TGC at the endcap of ATLAS; (b) Translate the package for ARGO experiment. HEP & NP, 2003, 27(9): 813-818 (in Chinese) Journal of Shandong University, 2003, 38(5):80-85 (in Chinese) Talk given in the Workshop of ARGO Experiment, Beijing, Dec. 2002


Postdoctoral researcher

2004.7 --- present Institute of High Energy Physics, Beijing, China

Work on the ' radiative decays:

2002.4 --- 2004.7 Institute of High Energy Physics, Beijing, China

Thesis on 'Vector + Pseudoscalar, published on

Phys. Rew. D 70, 112007 (2004); Phys. Rew. D 70, 112003 (2004);

Phys. Lett. B 614 (2005) 37-43; HEP & NP, 2004, 28(10):1021-1025(in Chinese)

Talk given at the 40th Rencontres de Moriond on QCD and High Energy Hadronic Interactions, La Thuile, Italy, Mar. 2005 (hep-ex/0505044)

Coordinator of the working-group on ' radiative decays

Measurement of (2S) decays into and

(To be submitted to PRD soon) KK

IntroductionIntroduction Measurement of Measurement of ’’++–– Measurement of Measurement of ’’ SummarySummary

pγp

Outline

The The BBeijing eijing EElectron lectron PPositron ositron CCoolliderllider

EEcmcm~~2-5 GeV2-5 GeV

L L ~5~5101030 30 /cm/cm22ss at J/ at J/

~1~110103131/cm/cm22ss at at ''

AA unique unique e e++ee-- machine machinein the in the -charm energy-charm energyregion since 1989!region since 1989!

(CESRc is operating!)(CESRc is operating!)

Beijing, China

BESII DetectorBESII Detector

VC: xy = 100 m TOF: T = 180 ps counter: r= 3 cm MDC: xy = 220 m BSC: E/E= 22 % z = 5.5 cm dE/dx= 8.5 % = 7.9 mr B field: 0.4 T p/p=1.7%(1+p2) z = 3.1 cm

6.42 pb–1 @3.65GeV

About 1/3 of the Luminosity of '

Charmonium Spectrum

0

2

4

6

8

10

12

14

MKI MKII MKIII CBAL BESI BESII CLEOc

'

14M BESII

3M

DD

' physics at BESII

M. Appelquist and H. D. Politzer, PRL34, 43 (1975)

Test theoretical predictions, such as “12% rule”

predicted by pQCD

12%B

B

B

BQ

eeJ/ ψ

eeψ'

XJ/ ψ

Xψ'h

' physics

' decay (VP, VT, PP, NN, ……)

Clue to study ‘ and J/ decay

hc(1P1) via ' 0hc

' physics

J/ decays via '+–J/ when systematic

error is dominant

(21.880.052.01) 10–3 from 58M J/ data

(20.910.211.16) 10–3 from 14M ' data

(21.0 1.2) 10–3 (combined) BES, PRD 70, 012005 (2004)

cJ decays via ' cJ

Hadron spectrum, (f0(600)) in '+–J/

Br(J/3 )

' physics Few studies have been done for the ‘

radiative decays. Search for or study glueball candidates; Search for new decays of ’ and cJ; Prepare for the projects at BESIII.

’ radiative decay ’ cJ transition

C

C

(3) CLEO : with 5 times larger sample

(2) L3:

Gluonium production is presumably suppressed in collision.

Study the (1405/1475), named (1440) before

Measurement on Measurement on ''++––

eVKKBR 2350212))1440(())1440((

eVBR 95))1440(())1440((

eVKKBR 89)())1440((

(1) (1475) could be 1st radial excitation of ', with the (1295) being

1st radial excitation of . (1405) has a large gluonic content

148112 MeV

L3 collab., Phys. Lett. B 501 (2001) 1-11

CLEO collab., Phys.Rew. D 71, 072001 (2005)

Search new decay modes of ‘ and cJ

Test the “12% rule” in the ‘ radiative decays

'+–

(4) Studied in J/ with +–, , 0 and +–+–.

With the J/ results, we can deduce we can observe the

signal of ’ (1475/1405) +– and KK.

KK

• Two good charged tracks with net charge zero

• Each charged track identified to be candidate

• Three good photon candidates

• 24C(+–3)<15

'+–

To reject the background

from '+J/

To suppress the back-

ground from 'X1+J/,

J/ + + X2

m()

Mass recoiling from

'+–

not from decay

Sig. MC

Sig. MC

DATA

J/

DATA

Study the background with:

(1) PDG ; (2) 14M Lund-MC sample for 'X inclusive

Lund-MC('X ): describe data in quality, but maybe not in quantity.

Br. are different: J/ 3, 2.10% from BESII; 1.87% in Lund-MC

'+–

DATA Lund-MC

m()m() m()

Continuum

J.C. Chen et al., Phys. Rev. D 55, 5657–5666 (1997)

N(104) Br(10-5) Channel with

'+–

1,

2,

3,

4,

m()

Measured

No survive

These channels can only describes

about 40% of the total Bg. in DATA

Method with Lund-MCMethod with Lund-MC

14M Lund-MC sample

(1) Signal

Channel

(2) Known Bg. Channels

With large contribution

(3) The other Bg. Channel(s) with small contribution

+– +–0,

X+J/, J/ 3, K+K– 0

simulated separately

Lund-MC without channels in Part

(1) and (2)

Modified,then put back

Change the Br. of:

1, +–; 2, XJ/ ,J/ 3;

3, +–0; 4, J/ ,J/ K+K– 0

Lund-MC

m()

Br. Changed

Signal taken out

m()

+ continuum

'+–

Sig.: two-Gaussian(MC)

Bg.shape: Legender

Method to Background:Nsig.= NDt. ― NBg.

(Nsig.) = (NDt.)

(NBg) taken as sys. of Nsig.

NDt.=553.260.2

NBg. =134.952.226.8

6.6

'+–

candidates: sidebands:

6.6

‘(958)

NDt.=24.25.4; NBg. =0.91.4 1.4

(1405)

NDt.=13.87.0; NBg. =4.04.5

Background events estimated

from sidebands

'x, x+–

Get Nupper at 90% C.L. with Beyesian approach

'x, x+–

Nevt.

(1405)Nevt.=24

(1475)Nevt.=20 L

i/L

o

Li/

Lo

8.8

NDt.=255.928.0

NBg. =34.1 15.4

Suggest two-body

decay of c1

'x, x+–

a0(980) candidate:

4.5

NDt.=79.014.2;

NBg. =21.2 11.1

'c1, c1 a0(980)+ +c.c.

a0(980) sideband:

m in (1.3---1.9) GeV

NDt.=65.212.9;

NBg. =12.2 7.0

4.8

'c1, c1f2(1270)

and f2(1270)

candidates:

Sideband from and f2(1270)

'c1, c1 a0(980), f2(1270)

I. cross-contamination is considered.

II. Interference is not considered (low statistic)

Contamination from c1 a0

to c1f2 can be considered

with f2(1270) sideband

Contamination from c1f2

to c1 a0 can be considered

with a0(980) sideband


QED Background

(1)Contamination to signal

has been considered

(2) No contamination to ' and c1

Detection Efficiency

Simbes: based on Geant3

Angular distribution is considered

cos

(1+cos2)

(1-cos2 /3)

‘’, (1405) 'c1

Eff. is weighted average for: ‘+– , c1 +–

Systematic errorSystematic error

Conventional ones

Int.: Uncertainty in Br. of resonances: , ‘ c1, ’ +–

: Statistic of MC sample and of sub-processes for weighted Eff.

Fit: Uncertainty in selection of Bg. shape and mass region to fit

Results of Results of ’’++––

1, Improve the result of ’’,’+–:

2, The other results are all the first-time measurements

3, Upper limits are set for ’(1405/1475)+–


● Call on a working-group (8 members) to

study ‘ decays into + n-prong final states

a) +–, K+K– and pp-barb) +(+–+–, +–K+K– , K+K–K+K– , +–pp)c) +(+–+–+–, +–+–K+K–)

Measurement of Measurement of ' ' pppp

1 Two good charged tracks and Qi=0

2 Good photon number ≥ 1

3 With the photon with the largest energy, a 4C-fit is performed, and the Prob(2

comb , ndof )>0.01 2

comb= 24C +(i

2dE/dx + i

2TOF)

c

1, Clear cJ is observed

'pp

m(pp)E

vent

s/20

MeV

Eve

nts/

10 M

eV cJ

2, Only study the signal

with mpp<3.0 GeV

a) Mainly on signals

other than cJ

b) Background at 3.1 GeV from ‘x+J/


Background of 'pp

1, Background without pp, neglected.

dE /dx

TOF

’

2, Background from QED


a) ' x1+J/, J/ x2+pp

Background of 'pp

b) '

4, Background like pp + n

Neglected

pp + 20, 30, 20(neglected)

Measured

3, Background like pp + +–

DATA

Background

Ntot =381

NBg.=218.8

NQED =16*3.0

Nsignal=114.2

'pp

m(pp)

1, QED

2, ' pp + nE

vent

s/20

MeV


'pp

pp

pp0

pp0

pp00

2(4C) distribution

DT.1, Sig.

2, Bg.

3, QED

Proved by the Lund-MC result

Background has been

considered well

'pp

Components in the fitting

1, Sig.; 2, Bg. ; 3, QED.

Failed to add other component with Legender of order 1 or 2

' X, Xpp

Eff

.

dB/dm=(Nobs–Nbg)/ (•N' •m)

'pp

m(pp) m(pp)

dB/d

m (

10–5

/100

MeV

)

'pp

For mpp<3.0 GeV: Br.('pp)=(2.23±0.45±0.51)×10-5

Ana

lysi

s re

sult

dB/dm (10–5 /100 MeV)

Sys

. err

or

Nevt=21.8±7.8; Eff. =28.5%

'pp

c

Br(‘c, cpp)=(0.55 ±0.20 ±0.07)×10-5

m(pp)

Eve

nts/

10 M

eV

Phys. Rev. Lett. 91, 022001 (200

3)

Nevt=21.7±8.5

m(pp) – 2mp

Eve

nts/

20 M

eV

PDG: (0.36±0.14) ×10-5


Measurement on Measurement on ’’++––

First measurement of the Br. of ’+–

SummarySummary

Improvement in the Br. of ''(958), (2.00± 0.59±0.29) ×10-5 reported by BESI


First search for (1405/1475) with '+–

SummarySummary

J/(1405/1475)KK = (2.8 ± 0.6)×10-3

J/(1405/1475)+– = (3.0 ± 0.5)×10-4

'(1405) KK <0.8 ×10-5

'(1475) KK <1.5 ×10-5

'(1405) +– <1.6 ×10-5

'(1475) +– <0.83 ×10-5

Seem different from J/ decay


First observation for c1+–, f2(1270),

a0(980)+ + c.c.

For the test of “12% rule”, ''(958) is suppressed,

’+– is consistent with.

SummarySummary


First measure the branching ratio of ’

for mpp<3.0 GeV.

pp

Measurement on Measurement on ’’

SummarySummary

pp

Report the differential branching ratios of

’ for mpp<3.0 GeV for the first time.pp


There seems the near-threshold enhancement

in mass spectrum pp

SummarySummary

New method (fitting the 2(4C)) is developed to

estimated background quantitatively

First working-group is organized, and is highly

praised by the professors


These analyses will be good topics These analyses will be good topics for BESIII (for BESIII (3.2 3.2 10 1099/year for /year for ''))

SummarySummary

Study (1405/1475) with '+–

Study c1+– about interference between

c1 a0(980) and c1f2(1270)

Study the near-threshold enhancement 'pp


That’s all!That’s all!

Thank you!Thank you!谢谢谢谢 !!

FinishedFinished


The “12% rule”

M. Appelquist and H. D. Politzer, PRL34, 43 (1975)

12%B

B

B

BQ

eeJ/ ψ

eeψ'

XJ/ ψ

Xψ'h

This is the famous (or notorious)

“12% rule”.


‘‘++

NDt.=65.212.9;

NBg. =12.2 7.0

4.8

'c1, c1f2(1270)

m()

Weighted Average for Weighted Average for


Background of 'pp’ pp0 ’ pp00

(1.75 0.21)10-4


mpp

(G

eV)

Momentum of p or p

CLEOc and BESCLEOc and BESDataData BESIIBESII CLEOcCLEOc

J/J/ 58 M58 M ----

’’ 14 M14 M 3 M3 M

’’’’ 33 pb33 pb-1-1 281 pb281 pb-1-1

ContinuuContinuumm

6.4 pb6.4 pb-1 -1 ((s=3.65 GeV)s=3.65 GeV) 21 pb21 pb-1 -1 ((s=3.67 GeV)s=3.67 GeV)

PerformancPerformancee

BESIIBESII CLEOcCLEOc

p/pp/p1.7%/1.7%/1+p1+p22 0.6%@p=1G0.6%@p=1G

eVeV

E/EE/E22% /22% /EE 2.2%@E=1G2.2%@E=1G

eVeV

PartIDPartID dE/dx+TOFdE/dx+TOF dE/dx+RICHdE/dx+RICHCoverageCoverage 80%80% 93%93%

X(1835) X(1835)

X(1835)

'/J '

BES Preliminaryhep-ex/0508025

6.0

Observation of X(1835)

' '

'

5.1

veto,,0

Shape of phase space

Data selection: mass cut part ID kinematic fit ’ mass cut

Combine two ’ decay modesX(1835)

2

2

MeV/c 7.73.207.67

MeV/c 7.21.67.1833

54264

M

Nobs

410)4.04.02.2()()( XBXJB

Fit with BW + polynomial backgrounds, considering mass resolution.

Statistical significance: 7.7

BES Preliminaryhep-ex/0508025

Mass res. ~ 13 MeVEfficiency ~ 4%

What is X(1835)?

2

2

MeV/c 7.73.207.67

MeV/c 7.21.67.1833

:resultsy preliminar BES

M

Mass comparableWidth differentNo 2’ yetNo JP from BES

In PDG’05:

1842

225

What is X(1835)?

MeV 7.217.67

MeV 7.67.1833

:resultsy preliminar BES

M

Mass agreeWidth not contradictNo JP in both cases

In PDG’05:

Include I=0 FSI correction (hep-ph/0411386), refit BES ppbar mass spectrum

BES preliminary:

M = 18317 MeV

< 153 MeV

BES: PRL91, 22001 (2003)

30 1859627

What is X(1835)?

Further arguments support X(1835)=X(1859)=ppbar bound state:• ppbar bound state couples to ’ large [G.J.Ding and M.L. Yan, PRC72, 015208 (2005)]• ppbar bound state couples to ppbar strong [S.L. Zhu and C.S. Gao, hep-ph/0507050]

51.90.8

4

10)0.4(7.0)pp)B(XγXψJB(

100.4)0.4(2.2)ηππ)B(XγXψJB(

More data, more experiments, more information needed

• mass and width, most importantly JP

• more decay modes• more calculations

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

M=1859 MeV/c2

< 30 MeV/c2 (90% CL)

J/pp

M(pp)-2mp (GeV)0 0.1 0.2 0.3

3-body phase space acceptance

2/dof=56/56

acceptance weighted BW +3 +5

10 25

pp

BES II

Phys. Rev. Lett., 91 (2003) 022001

BESIIIBESIII

BEPCII:BEPCII: a high luminosity double–ring collidea high luminosity double–ring colliderr

The BESIII DetectorThe BESIII Detector

Be beam pipe

SC magnet Magnet yoke

& -counter

Drift Chamber

CsI(Tl) calorimeter

TOF

Charmonia Productions at BESIIICharmonia Productions at BESIII

Limited by existing tunnel

42 1022.73

:spreadenergy Ecm bE

Ecm=3.097 GeV =0.93 MeVEcm=3.686 GeV =1.3 MeVImportant for narrow resonance like J/ or ’.

Events Productions at BESIIIEvents Productions at BESIII

Huge numbers of J/ or ’ in one year’s running ---So the accelerator and detector optimized for D physics!

PhysicsPhysics EcmEcm Peak Lum.Peak Lum.(10(103333cmcm-2-2ss-1-1))

Cross SeCross Sec.(nb)c.(nb)

EventsEvents

/ year/ year

J/J/ 3.0973.097 0.60.6 34003400 10 10 10 1099

(2S)(2S) 3.6863.686 1.01.0 640640 3.2 3.2 10 1099

(3770)(3770) 3.7703.770 1.01.0 7.47.4 37 37 10 1066

(4040)(4040) 4.0404.040 0.60.6 9.29.2 28 28 10 1066

(4160)(4160) 4.1604.160 0.60.6 6.26.2 19 19 10 1066

3.6703.670 1.01.0 2.42.4 12 12 10 1066

DDbarDDbar 3.7703.770 1.01.0 66 30 30 10 1066

DDSS 4.0304.030 0.60.6 0.30.3 0.9 0.9 10 1066

DDSS 4.1404.140 0.60.6 0.60.6 1.8 1.8 10 1066

Average Lum. = 0.5×Peak Lum; and 1 year = 107s data taking time

Project ScheduleProject Schedule

June 2003 R&D and prototype May 2004 BEPC run•Jan. 2004 Jun. 2006 Construction•May 2004 Nov. 2004 BESII dismounting/Linac upgrade •Nov. 2004 Jan. 2005 Linac commissioning•Jan. 2005 Jun. 2005 SR run•Jul. 2005 Apr. 2006 Storage ring assembling•Jan. 2006 June 2006 Commissioning of storage ring•Dec. 15, 2006 Move BESIII to beam-line•Jan. 2007 Commissioning machine & detector•Feb. 2007 Test runphysics run

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Radiative Decay at BESII