Ain’t They Charming and Strange Jianchun (JC) Wang Syracuse University University of Rochester 11/18/2003 —A Review to The Recent D sJ Discoveries

Ain’t They Charming and Strange

Jianchun (JC) WangSyracuse University

University of Rochester 11/18/2003

—A Review to The Recent DsJ Discoveries

11/18/03 Jianchun (JC) Wang 2

What Do We See in This World ?

~1000 m 1738 km 30,000 lyrs

~1.8 m~1 cm< 1 m~

~100 m


What Is the World Made of ?

Empedocles

Wood Earth

Fire

Wuxing Theory

MetalWater


What Are Fundamental Components of This World ?

Helium atomsize in atoms size in meters

1 1010

np

p nn p

10141

10,000

p 10151

100,000

e q10181

100,000,000 at largestAre quarks and

electrons fundamental?


Quarks and LeptonsThe Standard Model

explains what the world is and what holds it together.

Antiparticles look and behave just like their corresponding matter particles, except they have opposite charges.

Q (e)

Q (e)


The Four Forces

Gravity

Graviton(not yet observed)

All

Weak

W+ W- Z0

Quarks and Leptons

Strong

Gluon

Quarks and Gluons

Electromagnetic

Photon

Quarks and Charged Leptons

And W+ W-

Force

Carried by

Acts on

(Electroweak)

Spin=2?


No Free Quark Observed

Baryonu

d

u u

d

uproton anti-proton

Q

Q

Mesonc

s

c

sDs

Ds

Q Q

c

u

u

s

g

g

c

sg d

u

sd

u

These states are also allowed.

Introduction ofThe Charmed-strange Mesons


Charmed-strange Mesons

scL Sc

Ss

L = 0221

states

L = 1223

L = 2225

Spin-Orbit

j L + Ss

j = 1/222

j = 1/222

j = 3/224

Tensor Force

JP = 0

1

JP = 1

3

JP = 0

1

JP = 1

3

JP = 1

3

JP = 2

5

J j + Sc L + S

Mixing

mostly j = 3/2

mostly j = 1/2


Preferred Decay Channel

1. Strong decay with j, isospin conserved, e.g. +0.

2. Strong decay with j not conserved, e.g. D2*+(j=3/2)D0(j=1/2)+

(j=0).

3. Strong decay with isospin not conserved, e.g. (2S) J/ 0.

4. Electromagnetic decay, e.g. 0

5. Weak decay, e.g. +

All decays must conserve energy, charge, momentum, and total angular momentum, lepton number, baryon number.

Most preferred

Least preferred


Brief History of DsJ Discoveries

Prior to 2003 All 4 discovered states

are very narrow. DS through weak decay.

DS* DS & DS0.

Ds1(2536) is a member of j=3/2 doublet (may include small admixture of j=1/2). It decays to j=1/2 in D-wave.

DsJ(2573) decays also in D-wave.

How about the other two missing states?


How Does Potential Model Work on D Mesons?

JP m(GeV) (MeV) Decays to

Expected m(GeV)

1.865 0 1.868

2.007 0 D 2.005

2.290 305 D 2.377

2.461 290 D* 2.490

2.422 19 D* 2.417

2.459 23 D,D* 2.460

DiPierro & Eichten

PRD64 (2001) 11404

Predictions


Potential Model Calculation


Prediction on Masses of DsJ Mesons

Potential models predict the mass and width of charm mesons (e.g. DiPierro & Eichten ), which worked quite well with D and DsJ mesons that were already known.

The j=1/2 doublet 0+ & 1+ were predicted to be massive enough to decay into DK and D*K respectively via S-wave. So the widths were expected to be broad.

Although there were predictions of lower mass, not much attention was paid.

Virtually “everyone” believed that D(*)K were the modes to look at, and they were difficult to be seen due to the width.

DiPierro & Eichten

PRD64 (2001) 11404


DS0 structure at 2317 MeV,

~ 40 MeV below DK threshold.

“… This result will send theorists back to their

drawing boards.”

The Experiments Involved


e e

e+e(4S)BBhadrons

How Particles are Produced?

e eeee e

eeqqhadrons

e e

(e+e(4S)BB) ~ 1 nb

(e+e qq) ~ 3 nb

(e+e cc) ~1.3 nb

M(e+e(GeV)


The BaBar Experiment

Asymmetric collider: 9.0GeV e + 3.1GeV e+.

Bunch crossing rate:~ 4.2 ns.

L = (6.6 1033) cms

L dt = 91 fb1 used

~100 million cc produced


The Belle Experiment

KLM

CsI

PID

SVD

TOF

e

e+

CDC

1.5T Magnet

Asymmetric collider: 8.0GeV e + 3.5GeV e+.

Bunch crossing rate: ~ 2.0 ns.

L = (1.06 1034) cms

L dt = 87 fb1 used


The CLEO II Experiment

Symmetric collider: 5.29 GeV e + 5.29 GeV e+.

Bunch crossing space: ~ 14 ns.

L = (1.25 1033) cms

L dt = 13.5 fb1 used


The CDF Experiment

L = (5 1031) cms

L dt = 300 pb1 used

c ~ 400 b (central)

Symmetric pp collider: 980 GeV p + 980 GeV p.

Bunch crossing rate: ~ 396 ns.

Discovery of Two New States


M(DS0) [GeV]

BaBar Discovered DS(2317)

The angular distribution is flat. As the final state is 00, the resonance is possibly JP=0+ (0+,1,2+).

Could it be the missing 0+ DsJ state or just a reflection?M(DS

0) [GeV]

DS++,K*0KK+K+

N = 1267 53M = (2316.8 0.4) MeV = (8.6 0.4) MeVP(DS0) > 3.5 GeV.

DS++0K+K+0


M (DS+[GeV]

Could The Resonance Be Real?

DS*+

Reflections?

“This mass corresponds to the overlap region of the DS*DS and DS(2317)DS0 signal bands that, because of the small width of both mesons, produces a narrow peak in the DS mass distribution that survives a DS* selection.”

Even if it is real, it could not account for the whole peak at 2317 MeV.

1. Reflection of known charm decay with some decay products missing?

2. Reflection of any decay with decay products mis-identified?

3. Reflection of unknown decay modes with some decay products missing?

4. ……They also noticed a peak at 2.46 GeV.


CLEO Confirmed DS(2317)

M> = (349.4 1.0) MeV = (8.0 1.3) MeV

P(DS0) > 3.5 GeV

DS* CLEO quickly confirmed the narrow resonance at 2317 MeV. They noticed a slightly broader width than detector resolution (6 MeV).


10M> = (349.8 1.3) MeV

= (6.1 1.0) MeVP(DS*0) > 3.5 GeV

CLEO Discovered DS(2460)

CLEO observed a significant peak in DS*0 spectrum at ~2.46 GeV.

Could it be the missing 1+ DsJ meson, or purely a reflection (feed-up) of DS(2317)?

M(DS)M(DS) [GeV]

Eve

nts

/ 5 M

eV


How Does Feed-up Happen?

2317

0

DS

2317FakeDS*

Fake2460

The feed-up peak has two interesting features distinct from the real signal peak.

1. If we consider the mass of DS* be shifted, it should not affect the feed-up peak other than a little shift.

2. The extra results in smearing of the peak.


DS0 Scatter Plot DS(2460)DS0

MC

DS(2317)DS0

MC


DS* sideband

DS* signalN = 55 10

!?

DS* Sideband Spectrum

There is a small enhancement in the normalized spectrum of DS* sidebands; But it accounts for only ~20% of the signal.


Significance of DS(2460) Signal

N = 42.4 ± 9.7

<M> = (351.2 ± 1.7 ± 1.0) MeV

= (5.3 ± 1.1) MeVSignificance = 5.7

M = (2463.6±2.1) MeV

Function in the fit

Gaussian function+ 2nd polynomial function+ DS* sideband spectrum


DS0 Monte Carlo SimulationsDS(2460)DS*0

signal MC

= 6.6 0.5 MeV

DS(2317) does “feed up” to the DS(2460) by attaching to a random .

However, the probability is low (~17% with floating width, ~9% with width fixed to that of data), and the width is 14.9 MeV rather than 6.6.

DS(2317)DS0 signal + random

= 14.9 0.6 MeVMuch wider than 6.1±1.0 MeV


Feed-down Also Happens

2460

0

DS*

Fake2317

The absence of the soft results in smearing of the peak.

DS


DS0 Monte Carlo Simulation

DS(2317)Ds0 signal MC

= 6.0 0.3 MeV

DS(2460)DS*0 signal with photon skipped

= 14.9 0.4 MeV

DS(2460) also “feed down” to DS(2317) with very large probability (~0.84

with width fixed to that of data). The width is 14.9 MeV rather than 6.0 MeV.


Cross-feed of Two DsJ Mesons CLEO data MC:

DS(2317)DS0

MC: DS(2460)DS0

Reconstruct as DS0

=8.0±1.3 MeVN=190±19

=6.0±0.3 MeVEff. 1 = %

Neglect the =14.9±0.4 MeV=0.840 (=8.0)

Reconstruct

as DS*0

=6.1±1.0 MeVN=55±10

Pick up a random

=14.9±0.6 MeV=0.091 (=6.1)

=6.6±0.5 MeVEff. 0=%

DS(2317) signal = 155 23 (+ ~18% feed-down) consistent with double Gaussians fit.

DS(2460) signal = 41 12 (+ ~25% feed-up) consistent with fit to sideband subtracted spectrum.


Double Gaussian Fit Fit the spectrum with double

Gaussian functions for the peak.

Narrow Width

Broad width

Single Gaussian

Data 6.01.2 16.56.3 8.01.3

MC 6.00.3 14.90.4

Eve

nts/

5MeV

/c2

Determine the mass without the effect of reflection.

<M> = (350.0 ± 1.2 ± 1.0) MeV

M = (2318.5 ± 1.7) MeV

The amount of reflection in the fit is consistent with calculation.


Belle Confirmed Both States

M(DS0)M(DS) (GeV)

DS(2317)

M(DS*0)M(DS*) (GeV)

DS(2460)

~30% of signals in the peak is due to feed-up from DS(2317).


BaBar Confirmed DS(2460)

After careful study of the cross-feed, BaBar confirmed the existence of DS(2460).

Feedup rate at BaBar as a fraction of the 2460 signal size is ~50% compared with CLEO (~25%) & Belle (~30%).

sidebandbackground

Fit to sideband subtracted data.

Cross feed makes it difficult to measure the mass.

M=M(DS*0)M(DS*) (GeV)


Belle Observed DsJ in B Decays

1+

2+

cos (helicity angle)

DS(2460)DS*0

DS(2460)DS

DS(2317)DS0


Mass and Width of The New States

M2317 –M2460 = 2.4 ± 1.0 MeV

Ds(2460) < 5.5, Ds(2317) < 4.6 MeV 90% C.L.

BaBar

CLEO

Belle (cont.)

Belle (B)

Average 349.10.6 346.70.8

345.61.01.0

351.32.12.0 346.81.62.0

350.01.21.0

348.70.50.9 346.00.60.9

351.21.71.0

348.80.40.8

M Ds(2317)–MDs(1969) (MeV) M Ds(2460)–MDs(2112) (MeV)


Production of The New States

0S S

0S S

0.44 0.13 0.02

0.25

CLEO(D (2460) D )

0.03 0.03

0.29 0.06 0.0

BaBar(D (2317) D )

Belle3

BB

Production ratios of the two new states are consistent in different experiments

The production rates of DsJ produced in eeqq are for P>3.5 GeV.0 2

S S S(D (2460) D ) (D (3.5 0.9 0.2) ) 10 B0

S S S2(D (2317) D ) (D ) (7.9 1.2 0.4) 10 B

*S S S(D (2112) D ) (D 0.59 0.03 0) .01 B

By CLEO

4.5 43.9

0S S SB DD (2460) D (2460 (17.) D 8 5.3) 10

B B 2.6 4

1.90

S S SB DD (2317) D (231 (8.5 2.6)7) D 10 B B

S S1.3 41.2SB DD (2460) D (24 (6.760) D 2.0) 10 B B

Production in B decays (by Belle).

Possible Explanations and Search of Other modes


Possible Explanations

Barnes, Close & Lipkin: DK molecule. (hep-ph/0305025)

Szczepaniak: D atom. (PLB 567 (2003),23)

Several authors: four quark particle. (Cheng & Hou, PLB 566(2003)193; Terasaki, PRD68(2003) 011501; Nussinov, hep-ph/0306187)

Van Beveran & Rupp: use a unitarized meson model to explain the low mass as a kind of threshold effect. (hep-ph/0305035)

Cahn & Jackson: use non-relativistic vector and scalar exchange force. (hep-ph/0305012)

……

Several possible explanations appeared after the discovery, some are quite exotic.


DK Molecule Why DK molecule?

Since the decay products are DS0, it is nature to think that the resonance contains charm and strange quarks.

As the 0+ cs meson is expected to be ~2.48 GeV and broad, this resonance might be a non-conventional meson.

The mass difference between D, D* is ~ 142 MeV, this results in the mass difference of DS(2460) and DS(2317).

Resonances f0, a0 are possible KK molecule.

What is the difference between molecule and four quark state (baryonium)? The difference between molecule and baryonium is not that obvious. A baryonium needs no “fall-apart” decay while molecule needs. It may not exist or has to be broad. On the other hand, isospin violation may hold it together and results in narrow width.

Anything to observe? One can search for I=1 resonance like DS. One can study in B decays the D+Kmolecule which decays to KK++. If it is normal cs meson, one expect that the width of mode DS* to be =2keV. If it

measurement shows very much different, it got to be other things.

c

u

u

s


Pentaquark State +

Experiment Mode Mass (MeV) Width (MeV) Signif.

LEPS at Spring-8, Japan Kn 1540 10 < 25 4.6

DIANA at ITEP Kp 1539 2 < 9

CLAS at JLAB Kn 1542 5 21 (resolution)

SAPHIR at ELSA Kn 1540 4 2 < 25

LEPS

n

K─

K+

n+

p p

du

sd

u


Search For DS(*)

0

*

* 0

( )0.10 (90% )

( (2317) )

( )0.12 (90% )

( (2460) )

S

S S

S

S S

X DCL

D D

X DCL

D D

Upper limits from CLEO:

23172317

2460 2460

No narrow structures

I=0 for DS(2317), and DS(2460)

Narrow structures in DS(*) would

support molecular hypothesis due to quark contents (csud)0 and (csud)++.

Absence of narrow structure does not rule out the explanation as I = 1 is expected to be very broad.


Another Possible Explanation DS(2317) and DS(2460) fit in well the quark model as ordinary 0+

and 1+ DsJ mesons except for maybe the masses (~140-170 MeV below the expectation).

Bardeen, Eichten & Hill (hep-ph/0305049) couple chiral perturbation theory with a quark model representing HQET. They infer that the DS(2317) is the 0+ state, and predict the existence of the 1+ partner. The mass splitting between the partners is identical to that between 0 and 1: M(1+) M(0+) = M(1) M(0) 144 MeV.

DS(2317) and DS(2460) are below DK and D*K thresholds. The strong channel to DS0 and DS*0 are isospin suppressed. Thus the widths are very narrow.

The measurement ( M(1+) M(1) M(0+) M(0) 350 MeV ) backs up the prediction.

BEH also calculate the branching ratio of different modes.


Belle

Search for DsMode

Ds(2317)

Ds(2460)CLEO

CDF

Existence of Dswouldrule out JP=0+ possibility.

Ds1(2536) N= 5613

Ds(2460)N= 6012

Belle observed Ds(2460)Ds.S S

*S S

o

(D (2460) D )0.14 0.04 0.02

(D (2460) D )

BB

No Ds(2317)Dsis observed.


Ds(2317)

Ds(2460)

CLEO

Search for DsMode

Belle

S S*

S So

0.55 0.13 0.08, continuum(D (2460) D )

0.38 0.11 0.04, Bdecays(D (2460) D )

BB

No Ds(2460)Dsis observed.

Belle observed Ds(2460)Dsin both B decay and continuum and samples.

Dsmode is forbidden JP=0+.

BaBar

M(DS) GeV/c2


Search for Ds

andDs(2317)Modes

Ds(2460)

CLEO

Ds(2317) Ds(2460)

CLEO

Dsmode is allowed

for both JP=0+ and 1+.

Ds(2317)is allowed for JP=1+.

Absence of the mode indicates that the EM decay mechanism can not compete with DS*0 which might be a strong but isospin violating process.


Summary of Search for Other ModesDecay Channel Possible JP

Rule out JP

Branching fraction ratio/Limit (90% CL) BEH predictionBaBar Belle CDF CLEO

Ds(2317)

Ds0

Ds

Not seen <410-3 Not seen < 0.019 0

Ds Not seen

Ds0 Not seen Not seen

Ds Not seen <0.18

Ds(2460)

Ds0

Ds Not seen <0.31

Ds

Not seen < 0.21 Not seen 0

Ds

? 0.14 Not seen < 0.08 0.20

Ds Not seen 0.55

)

Ds(2317)

BEH’s chiral symmetry + HQET model prediction

is consistent with measurements.


Factorization Mystery

Four-quark state or molecule would have B consistent with measurement. (Chen & Li hep-ph/0307075; Datta & O’donnel hep-ph/0307106; Cheng & Hou hep-ph/0305038 )

2 2

22 2 212

( )6

( ) / S

DS

SD cs

q m

B D Dc f V

d B D l dq

Factorization implies the branching fractions be similar to BDDS. The measurements are a factor of ~10 lower than expectations.

4.5 43.9

0S S SB DD (2460) D (2460 (17.) D 8 5.3) 10

B B 2.6 4

1.90

S S SB DD (2317) D (231 (8.5 2.6)7) D 10 B B

S S1.3 41.2SB DD (2460) D (24 (6.760) D 2.0) 10 B B

( 2*)S (0.8 1.3B DD ) 1~ 0 B


Summary Two new states are discovered at ~2.32 GeV in DS0 mode and ~2.46

GeV in DS*0 mode.

The nature of the new states are not totally revealed yet.

They are favored to be j=1/2 doublet 0+ and 1+ DsJ states. Other explanations like molecule are not ruled out.

More experimental measurements and theoretical ideas are needed to reveal their true identities.

c

u

us c

s


Backup slides


The Charm Mesons


BaBar Presentation at FPCP 2003


CLEO Numbers in Continuum DataDS(2317)DS0 MC DS(2460)DS0 MC

Reconstruct as DS0 =6.0±0.3, 1 = % =14.9±0.4, =0.840

Reconstruct as DS*0 =14.9±0.6, =0.091 =6.6±0.5, 0=%

DS(2317)DS0 N=16520 (190 19), M=349.41.0, =8.01.3/1.1

DS(2460)DS*0 N=5510, M=349.81.3, =6.11.0

-- Solve cross feed: f0=0.0910.0070.015, f1=0.840.040.10

DS(2317)DS0 N=15523

DS(2460)DS*0 N=4112

-- sideband subtraction, DS(2460)DS*0 N=45.711.6, M=351.21.71.0, <7

-- two gaussians fit, DS(2317)DS0 M=350.01.21.0, =6.0 1.2, <7

Feed down M=344.96.1, =16.5 6.3 (M) =1.2 2.1-- Production of DsJ for P>3.5 over Ds production DS(2460)DS*0 rate = (3.50.90.2)10

DS(2317)DS0 rate = (7.91.20.4)10

DS*(2112)DS rate = 0.590.030.01


BaBar Numbers in Continuum DataDS(2317)DS0 MC DS(2460)DS0 MC

Reconstruct as DS0 =7.5±0.3 =

Reconstruct as DS*0 ~ 15 MeV =

DS(2317)DS0 N=126753, M=2316.80.43.0, =8.60.4, intrinsic<10,

DS(2317)DS0 (other DS mode) N=27333, M=2317.61.3, =8.60.4

-----------------------DS(2460)DS*0 M=346.20.9, sideband subtraction

-- Unbinned likelihood fit to M(DS0DS0),M(DS DS(2460)DS*0 N=19526, M=2458.01.01.0, =8.51.0, <10, angular disfavor 0-

M=345.61.01.0 DS(2460)DS(2317)N=023 ratio < 0.22 (95% CL)

-- Take into account the contribution of Ds(2460) from MC. DS(2317)DS0 N=102050, M=2317.30.40.8, =7.30.2 => M=348.80.40.8

*Br(2460)/ *Br (2317) = 0.250.03 0.03


Belle Numbers in Continuum DataDS(2317)DS0 MC DS(2460)DS0 MC

Reconstruct as DS0 =7.1±0.2 =14.9±0.8, M)=4+3.8

Reconstruct as DS*0 =12.3±1.8, M)=8.03.8 =6.0±0.2,=19.5±3.6

DS(2460)DS*0 N=12625, M=2456.51.31.3, M=344.11.3 1.1, =5.81.3, sideband subtraction, intrinsic<5.5

DS(2317)DS0 N=76144 30, M=2317.20.50.9, M=348.70.50.9, =7.6 0.5, 2-gaussian fit with fixed mass and width of MC for feed-down, intrinsic<4.6

*Br(2460)/ *Br (2317) = 0.29 0.0 0.03DS(2460)DS0 N=22 22, ratio<0.21

DS(2460)DSN=15218, M=2459.51.32.0, M=491.01.3 1.9, ratio=0.550.13 0.08 2-gaussian fit => M=347.11.3 1.9 DS(2317)DSratio<0.05

DS(2317)DS*ratio<0.18

DS(2460)DS*ratio<0.31

DS(2460)DS N=59.711.5, M=2459.90.91.6, M=491.40.91.5, ratio=0.140.040.02 => M=347.51.3 1.9DS(2317)DSratio< 4x10-3


Belle Numbers in B Decays

DS(2460)DS*0, DS M=2459.21.62.0 => M=346.81.6 2.0

DS(2317)DS0 M=2319.82.12.0 => M=351.32.1 2.0

DS(2460)DShelicity fit 2/ndof = 5/6 for J=1, 44/6 for J=2.

DS(2460)DSratio=0.380.11 0.04

S S*

S So

(D (2460) D )0.38 0.11 0.04

(D (2460) D )

BB

Documents

Ain’t They Charming and Strange Jianchun (JC) Wang Syracuse University University of Rochester 11/18/2003 —A Review to The Recent D sJ Discoveries