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
11/18/03 Jianchun (JC) Wang 3
What Is the World Made of ?
Empedocles
Wood Earth
Fire
Wuxing Theory
MetalWater
11/18/03 Jianchun (JC) Wang 4
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?
11/18/03 Jianchun (JC) Wang 5
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)
11/18/03 Jianchun (JC) Wang 6
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?
11/18/03 Jianchun (JC) Wang 7
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.
11/18/03 Jianchun (JC) Wang 9
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
11/18/03 Jianchun (JC) Wang 10
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
11/18/03 Jianchun (JC) Wang 11
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?
11/18/03 Jianchun (JC) Wang 13
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
11/18/03 Jianchun (JC) Wang 15
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
11/18/03 Jianchun (JC) Wang 16
DS0 structure at 2317 MeV,
~ 40 MeV below DK threshold.
“… This result will send theorists back to their
drawing boards.”
11/18/03 Jianchun (JC) Wang 18
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)
11/18/03 Jianchun (JC) Wang 19
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
11/18/03 Jianchun (JC) Wang 20
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
11/18/03 Jianchun (JC) Wang 21
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
11/18/03 Jianchun (JC) Wang 22
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.
11/18/03 Jianchun (JC) Wang 24
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
11/18/03 Jianchun (JC) Wang 25
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.
11/18/03 Jianchun (JC) Wang 26
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).
11/18/03 Jianchun (JC) Wang 27
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
11/18/03 Jianchun (JC) Wang 28
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.
11/18/03 Jianchun (JC) Wang 30
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.
11/18/03 Jianchun (JC) Wang 31
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
11/18/03 Jianchun (JC) Wang 32
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
11/18/03 Jianchun (JC) Wang 33
Feed-down Also Happens
2460
0
DS*
Fake2317
The absence of the soft results in smearing of the peak.
DS
11/18/03 Jianchun (JC) Wang 34
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.
11/18/03 Jianchun (JC) Wang 35
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.
11/18/03 Jianchun (JC) Wang 36
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.
11/18/03 Jianchun (JC) Wang 37
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).
11/18/03 Jianchun (JC) Wang 38
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)
11/18/03 Jianchun (JC) Wang 39
Belle Observed DsJ in B Decays
1+
2+
cos (helicity angle)
DS(2460)DS*0
DS(2460)DS
DS(2317)DS0
11/18/03 Jianchun (JC) Wang 40
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)
11/18/03 Jianchun (JC) Wang 41
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).
11/18/03 Jianchun (JC) Wang 43
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.
11/18/03 Jianchun (JC) Wang 44
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
11/18/03 Jianchun (JC) Wang 45
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
11/18/03 Jianchun (JC) Wang 46
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.
11/18/03 Jianchun (JC) Wang 47
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.
11/18/03 Jianchun (JC) Wang 50
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.
11/18/03 Jianchun (JC) Wang 51
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
11/18/03 Jianchun (JC) Wang 52
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.
11/18/03 Jianchun (JC) Wang 53
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.
11/18/03 Jianchun (JC) Wang 54
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
11/18/03 Jianchun (JC) Wang 55
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
11/18/03 Jianchun (JC) Wang 59
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
11/18/03 Jianchun (JC) Wang 60
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
11/18/03 Jianchun (JC) Wang 61
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
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