New States Associated with Charmonium from B A B AR and B ELLE Shuwei YE University of Texas at...

New States Associated with Charmonium

from BABAR and BELLE

Shuwei YE

University of Texas at Dallas

CLEO Seminar

October 12, 2005

CLEO Seminar October 12, 2005

Shuwei YE 2

Introduction: Charmonium Spectroscopy

The Experiments: BABAR and BELLE The Initial Surprise: X(3872)

New Heavy States: X(3940), Y(3940), Z(3930), Y(4260)

Properties of the X, Y and Z States

Interpretations and Theoretical Guidance

Summary

Outline


Shuwei YE 3

Mesons: Charmoniun States

Meson SpectroscopyCC

PCJ

c(2S), hc recently added by e+e experiments (CLEO-c, BELLE, BaBar)

?


Shuwei YE 4

Vector Charmonia

Vector charmonia:(4040), (4160) and (4415)

inferred from (e+e hadrons)/(e+e ) (inclusively)

(GeV)s

R


Shuwei YE 5

The BABAR Experiment at SLAC

~600 physicists from 80 institutes in 11 countries

(4 )e e S BB (4 ) 10.58 GeV Ss M

e-e+E =3.1 GeV, E =9 GeV =0.56, c~250 m


Shuwei YE 6

BABAR Detector

The BABAR Experiment at PEP-II


Shuwei YE 7

BABAR Data

(as of October 4, 2005)

Integrated Luminosity

Runs 1-3: L = 123 fb-1

Run 4: L = 109 fb-1

L = 232 fb-1 analysed

Run 5: L > 60 fb-1


Shuwei YE 8

The BELLE Experiment at KEK


Shuwei YE 9

The BELLE Experiment at KEK

~1 km in diameter

Mt. Tsukuba

KEKBBelle

8 GeV (e-) on

3.5 GeV (e+)

L=469 fb-1 collected

upto 350 fb-1 analysed

http://kekb.jp/


Shuwei YE 10

Belle Detector


Shuwei YE 11

Sources of New Mesons/StatesAssociated with Charmonium

Many productions are accessible at B-factories:

B decays

Continuum production

Two photon interactions (C=+1)

Double CC interactions in e+e- annihilations

Initial state radiation (ISR) ( JPC=1-- )


Shuwei YE 12

8.1significance

Discovery of the X(3872)

(2S)

Eve

nts/

10 M

eV/c

2

Belle157M BBbar

B± K± X(J/) PRL 91, 262001 (2003)

M(J/ ) - M(J/) (GeV/c2)


Shuwei YE 13

Confirmation of the X(3872)

X(3872) confirmed by CDF, D0 and BABAR

BaBarPRL 93, 072001 (2004)

PRL 93, 162002 (2004)

PRD 71, 071103 (2005)

220 pb-1 230 pb-1

M(J/) (GeV/c2)Eve

nts

/ 5

MeV

/c2


Shuwei YE 14

Evidence: X(3872) J/, J/

13.6 ± 4.4 X(3872)J/evts (>4significance)

M(J/)

X(3872)J/

Br(XJ/)

Br(XJ/)=0.14 ± 0.05

A virtual (782)?

X(3872)J/

M(0)

Br(X3J/)Br(X2J/) = 1.0 ± 0.5

Isospin Violation!


Shuwei YE 15

C=+1 is established

XJ/ only allowed for C=+1 same for X“”J/ (reported earlier) M() for XJ/ looks like a


Shuwei YE 16

Observation:X(3872)D0D00

11.3±3.6 sig.evts (5.6)

Br(BKX)Br(XDD)=2.2±0.7±0.4x10-4

Preliminary

Cannot distinguish

D0D00 and D0D*0

M(D0D00)


Shuwei YE 17

Properties of the X(3872)Mass = 3872.00.6 0.5 MeV/c2 , <2.3 MeV (90% C.L.)

very close to m(D0) + m(D*0)

0--

exoticViolates parity

0-+

(c”)

0++

DD allowed

(c0’)

0+-

exoticDD allowed

1- -

DD allowed

((3S))

1-+exotic

DD allowed

1++

favored

1+-

(hc’)

2- -

(2)

2- +

(c2)2++

DD allowed

c2’)

2+-

exoticDD allowed

253 fb-1 data:

Further angular analysis and the observation of X(3872)D0D00

1++


Shuwei YE 18

PRL 89, 142001

Belle found double charmonium

final states: (J/, (2S))(c, c) with surprisingly large cross-sections

No signal of C = -1 states in the J/ recoil mass spectrum

Confirmation by BaBar: large contradiction to NRQCD

PRD 72, 031101

e+e J/ cc

Cross-sections (fb)


Shuwei YE 19

X(3940) in e+e J/ cc at BELLE

M = (3943 6 6) MeV/c2

< 52 MeV (90% C. L.)

Stat. significance 5.0

or eeJ/

above DD and D*D thresholds

a new charmonium state350 fb-1

c(1S) c0

c(2S)

X(3940)

hep-ex/0507019


Shuwei YE 20

X(3940) DD

X(3940)DD: (No)

N = 0.2+4.4-3.5

Br (X(3940) DD) < 41% (90 C.L.)

X (3940)DD*: (YES)N=24.56.9 (5.0)=15.110.1 MeVM=39436 MeV/c2

Br (X(3940) DD*) = (96+45

-32±22)%


Shuwei YE 21

Y(3940) : near J/ threshold enhancementin BK J/ at BELLE

253 fb-1

If it is treated as a S-wave BW:

M = 3943 11 13 MeV/c2

= 87 22 26 MeV2/d.o.f. = 15.6/8

stat. sig. = 8.1

PRL 94 (2005) 182002

above D*D threshold

not clear BRs to DD or D*D final states

a ccg hybrid charmonium?


Shuwei YE 22

Z(3930) from two-photon events at BELLE Look at DD mass distribution in events (pt(DD)<50 MeV/c): N = 41 11 (5.5)

= 20 8 3 MeVM = 3931 4 2 MeV/c2

pt distribution is consistent with events

hep-ex/0507033

280 fb-1

hep-ex/0507033


Shuwei YE 23

Z(3930) from two-photon events at Belle

Study helicity angle distribution: clear tendency for small |cos| Helicity distribution is consistent with J=2 (~sin4 ); J=0 (flat) disfavored: 2=32.2/9 Z=c2‘

(2J+1) x B (Z DD)=(1.130.30)keV


Shuwei YE 24

Y(4260) from ISR at BABAR: Motivation

2S(3770), X(3872)+J/

Are there other vector charmonia or heavy particles that decay to +J/ ?

ISR process provides e+e collisions with a spectrum of energies

for e+e ISR

e+e ISR

Y, Y+J/

JPC= 1 J(2S), (3770), …

X(3872)(?)


Shuwei YE 25

Access e+e Annihilations through ISR

)(GeVs

BABARaccessible through ISR method

Probe physics with C.M. energies below 10 GeV using

Initial State Radiation (ISR) (X.C. Lou et al., Nucl. Phys. A675, 253 (2000))

which was validated with first BABAR data ISR (2S)

(X.C. Lou, Int. J. Mod. Phys. A16S1B, 486 (2001 ))

Search for new particles in e+e ISR interactions


Shuwei YE 26

Features of ISR Events

A small recoil mass against the hadronic system

Low missing transverse momentum

Preferentially along the beam directions

Selection criteria makes use of these ISR features


Shuwei YE 27

First Indication in ISR +J/

An enhancement around 4.3 GeV/c2

J/e+e or

• L = 123 fb-1

• >5k (2S): little bkg

• No evidence for X(3872),

but …

ISR (2S) X(3872)


Shuwei YE 28

Selection Optimization of 232 fb-1 Data

Optimize the selection by the quantity S / (3/2+ B ) where 3/2 corresponds to the search for a 3-signal (G. Punzi physics/0308063)

S = N((2S)): clean ISR (2S) as signal calibration

B = N(bkg) in [3.8,4.2] and [4.4,4.8] GeV/c2

from the data, scaled to the signal width

Blind region [4.2,4.4] GeV/c2 during optimization

There is no reliable MC for continuum J/combinatorial background

Data-driven optimization


Shuwei YE 29

Control Sample: ISR (2S) +J/

Mass calibration and resolution

Cauchy resolution function (Breit-Wigner shape)

N(obs.) = 11802 110

N(expect.) = 12142 809

M((2S)) – M(PDG04)

= -0.77 0.04 MeV/c2

(correction applied to data)

FWHM of Resolution Shape

= 4.2 MeV/c2

Data


Shuwei YE 30

Results for L = 232 fb-1 dataUnbinned likelihood fit with

Rel-BWPhaseSpaceReso

+ 2nd polynomial (BKG)

(2S)

N = 12523

Mass = 4258 8 MeV/c2

= 88 23 MeV

PRL 95, 142001(2005)

Y(4260)


Shuwei YE 31

Significance of the Y(4260) SignalMethod-1: Fit with null signal hypothesis

We try 1st, 2nd, and 3rd order polynomial

different bin sizes: 5, 10, 20, 40, 50 MeV/c2

Fit-Prob(2, dof) = 10-16 – 10-11 for null signal

Method-2:

Try Run-4 data with the original selection criteria for Runs 1-3

Independent of the optimized criteria Completely untainted(blind) to the Run-4 data

Significance = (2) or (-2ln(L0/Lmax))

5 – 7 for the Run 4 sub-sample alone (L = 109 fb-1)

Significance > 8 for the full sample (L = 232 fb-1)


Shuwei YE 32

Robustness and Optimization-Bias Checks

Data subset (2S) Fraction Y(4260) Fraction

Full data (232 fb-1) 1.0 1.0

Run 1+2+3 (123 fb-1) 0.55 0.61 0.09

Run 4 (109 fb-1) 0.45 0.45 0.09

J/e+e- 0.43 0.400.09

J/+- 0.57 0.57 0.10

With visible ISR 0.25 0.24 0.08

Good consistency between subsets for ISR (2S) and ISR Y(+-J/)

Reverse selection criterion one by one (individually)

Reverse selection criteria in pairs

No evidence of significant bias in any reverse selection.


Shuwei YE 33

Additional Checks

Are the selected J/ candidates real J/?

Are the selected ISR J/ events genuine ISR events?

Test by examining the kinematic distributions


Shuwei YE 34

Real J/

Apply Y-sideband

subtraction

The Y signal region: [4.16,4.36] GeV/c2

The Y sidebands: [3.86,4.06] + [4.46,4.66] GeV/c2

+-e+e-

Good agreement between Y Data and (2S) data and Y Monte Carlo

Eve

nts

/ 10

MeV

/c2

Eve

nts

/ 10

MeV

/c2


Shuwei YE 35

ISR Events ? (1)


e+e-

+-

Eve

nts

/ 0.1

GeV

/c


Shuwei YE 36

ISR Events ? (2)


Cosine of polar angle of J/

We do not tag the ISR

(only about 25% events with visible ISR)


Shuwei YE 37

Check for Reflections or Feeddowns

No peak to reflect from

ISR K+K-J/

(particle mis-ID )

No peak to feed from

ISR J/

(missing )


Shuwei YE 38

Other Backgrounds

No structure

(2S)

Feeddown of (2S)J/

Background from two-photon events is estimated by reversing the recoil mass criterion.

A mix of two- events + ISR events with additional neutral tracks


Shuwei YE 39

One vs Two Resonances

Hypothesis of two resonances

Two-resonance fit yields:

M1= 4251 6 MeV/c2, 1=58 18 MeV

M2= 4334 1 MeV/c2, consistent with the resolution

Fit-prob( is about 9.4% (not a significant improvement)

The single-resonance fit-probability( is about 2.6%

We cannot exclude or establish a multi-resonance hypothesis

No substantial improvement is obtained by including

the (4040), (4160) and (4415) in the fit


Shuwei YE 40

m() DistributionsISR (2S):

Good agreement between data and MC

where (2S)J/in MC is modeled

by multi-pole model (PR D22, 1652 (1980))

ISR Y(4260):

MC is phase space


Shuwei YE 41

Single-Resonance Results

For single-resonance hypothesis:

Mass = 4259 8-6+2 MeV/c2

= 88 23-4+6 MeV

Yee B (Y+-J/) =

Statistical significance > 8

JPC = 1– – (inferred from ISR production)

eVsysstat )()(0.15.5 8.07.0


Shuwei YE 42

Comparison with R-Scan R-scan plot (PDG04) shows a dip at 4.26 GeV

Peak cross section for (e+eY)B (Y+J/) is about 0.05nb

(e+e hadron) =14.2 nb @s=4.26GeV

and R-scan accuracy of 0.56 nb

Dip at 4.26GeV

R

sqrt(s) (GeV)


Shuwei YE 43

Implication from (YJ/) Partial width of established charmonium states:

(2S) (3770)

(+J/) 89 keV 45 keV (CLEO)

(e+e) 2.12 keV 0.26 keV

The Y width, a dip in R-Scan

and Yee B (Y+J/) = 5.5 eV

Large (Y+-J/) (>1 MeV), (Ye+e) < 0.35 keV

(assuming R<1/2 at 4.26 GeV in R-scan plot)

Difficult to interpret as a conventional charmonium ?


Shuwei YE 44

Theoretical Interpretations for Y(4260)

Charmonium state ( ) ? Hybrid ( ) ?

4-quarks (bag, molecule, diquark-antiquark) ?

From

1. S.L. Zhu, “The possible interpretations of Y(4260)”, PL B625, 212 (2005)

2. Felipe J. Llanes-Estrada “Y(4260) and possible charmonium assignment”,

PRD 72, 031503(2005)

3. L. Maiani, V. Riquer, F. Piccinini, A.D. Polosa “Four quark interpretation of Y(4260)”,

PRD 72, 031502(2005)

4. E. Kou, O. Pene, “Suppressed decay into open charm for the Y (4260) being an hybrid”,

hep-ph/0507119

5. Xiang Liu, Xiao-Qiang Zeng, Xue-Qian Li, “Possible molecule structure of the newly observed Y(4260)”, PRD 72, 054023 (2005)

6. Frank E. Close, Philip R. Page, “Gluonic charmonium resonances at BaBar and Belle?”,

hep-ph/0507199

gcccc


Shuwei YE 45

CLEO Can Help on Y(4260)CLEO can help resolve the Y(4260) structure (one/multi resonances?)

and understand what it is.

First-order cross-section at s = 4.26 GeV

(e+e Y(4260))B (Y(4260)+J/) 50 pb

(e+e ISR (2S))B ((2S)+J/) 110 pb

Advantages of running at s = 4.26 GeV:

Larger acceptance (a factor of 56)

Much larger production cross-section (a factor of 1.6x103)

Possible to tag +only, use recoil mass against +


Shuwei YE 46

Properties of New Heavy StatesName Mass

(MeV/c2)

Width

(MeV)

Production and decays What is it?

X(3872) 3872.0

0.60.5

<2.3 Produced in B-decays, XJ/, J/, D0D00

1++, Molecule?

X(3940) 3943

6 6

<52 Recoil J/, Large B (DD),J/ not seen

c(3S)?

Y(3940) 3943

11 13

87 22

26

Produced in B-decay, YJ/

hybrid?

Y(4260) 4259

8 +2-6

88 23

+6-4

J/ in ISR, D pair not seen, Dip in R-Scan

1, hybrid?

Z(3930) 3931

42

20 8

3

D pair in ’c2?


Shuwei YE 47

Summary Several new states/structure above (3770) have been

observed by BABAR and BELLE

Current statistics is not sufficient to establish the Y(4260) structure as a single-resonance or multiple resonances. It seems incompatible with the charmonium spectroscopy due to large (Y+-J/) .

Some of these heavy states defy the expectation for conventional charmonia.


Shuwei YE 48

Backup slides


Shuwei YE 49

The PEP-II B-factory


Shuwei YE 50

Optimized J/ Criteria

Candidates: J/ l+ l-

Well reconstructed tracks for both l

Require one e/ PID

J/ mass windows e+e-: [-95, +33] MeV/c2

(with bremsstrahlung recovery) +-: [-40, +33] MeV/c2

Cosine of lepton angle:

|cosl+ (J)|<0.90

Apply J/ mass-constraint to l+ l-

Arb

itrar

y U

nit

Eve

nts

/ 0.0

2


Shuwei YE 51

Optimized J/ Criteria

We do not require the ISR to be reconstructed

(only about 25% events with visible ISR)

Candidates: +-J/ Well reconstructed tracks for both

Require PID for both

No extra well-reconstructed track pt*(Miss) < 2.5 GeV/c :

Including ISR when detected :

momentum balance

ISR along beam directions if missing

+ helicity angle: cos<0.9 for e+e-

to remove soft beam-related e bkg Square of Recoil mass against +-J/ e+e-: [-1.06,+3.27] GeV2/c4

+-: [-1.06,+1.25] GeV2/c4

Arb

itrar

y U

nit

Eve

nts

/ 0.0

2

e+e-


Shuwei YE 52

Control Sample: ISR (2S) +-J/

M(l+l-): Good agreement between data and Monte Carlo

e+e- +-

Arb

itrar

y U

nit

Arb

itrar

y U

nit


Shuwei YE 53


Minor difference due to no secondary ISR in MC

Arb

itrar

y U

nit

Arb

itrar

y U

nit +-

Arb

itrar

y U

nit e+e-


Shuwei YE 54


Minor difference due to no secondary ISR in MC

Cosine of polar angle of J/ in CM frame:

preferentially along the beam directionsA

rbitr

ary

Uni

t


Shuwei YE 55

Original selection to Run-4 data Try the Run-4 data with the original Runs 1-3 selection criteria

Large fraction of signal-overlap

Statistical significance for this subset alone (-2ln(L0/Lmax)) 7

New States Associated with Charmonium from B A B AR and B ELLE Shuwei YE University of Texas at...

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