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

11/18/03Jianchun (JC) Wang2 What Do We See in This World ? ~1000 m 1738 km 30,000 lyrs ~1.8 m ~1 cm < 1  m ~ ~100 m

11/18/03Jianchun (JC) Wang3 What Is the World Made of ? Empedocles Wood Earth Fire Wuxing Theory Metal Water

11/18/03Jianchun (JC) Wang4 What Are Fundamental Components of This World ? Helium atom size in atomssize in meters 110  10 n p p n n p 10  ,000 p 10  ,000 ee q 10  ,000,000 at largest Are quarks and electrons fundamental?

11/18/03Jianchun (JC) Wang5 Quarks and Leptons The 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)

11/18/03Jianchun (JC) Wang6 The Four Forces Gravity Graviton (not yet observed) All Weak W + W - Z 0 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?

11/18/03Jianchun (JC) Wang7 No Free Quark Observed Baryon u d uu d u protonanti-proton Q  Q  Meson c s c s DsDs DsDs Q  Q  c u u s g g c s g d u s d u These states are also allowed.

Introduction of The Charmed-strange Mesons

11/18/03Jianchun (JC) Wang9 Charmed-strange Mesons s c L  ScSc  SsSs  L = 0 2  2  1 states L = 1 2  2  3 L = 2 2  2  5 Spin-Orbit j  L + S s  j = 1/2 2  2 j = 1/2 2  2 j = 3/2 2  4 Tensor Force J P = 0  1 J P = 1  3 J P = 0  1 J P = 1  3 J P = 1  3 J P = 2  5 J  j + S c  L + S  Mixing mostly j = 3/2 mostly j = 1/2

11/18/03Jianchun (JC) Wang10 Preferred Decay Channel 1.Strong decay with j, isospin conserved, e.g.  +  0  . 2.Strong decay with j not conserved, e.g. D 2 * + (j=3/2)  D 0 (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

11/18/03Jianchun (JC) Wang11 Brief History of D sJ Discoveries Prior to 2003  All 4 discovered states are very narrow. D S through weak decay. D S *  D S  & D S  0. D s1 (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. D sJ (2573) decays also in D-wave.  How about the other two missing states?

11/18/03Jianchun (JC) Wang12 Potential Model  Vector potential: Coulombic  Scalar potential: linear  Spin-orbit interactions L*S  Spin-spin interactions S c *S s  Tensor force ReferenceMass Ebert et. al. (98)2.51 GeV Godfrey-Isgur (85)2.48 GeV DiPierro-Eichten (01)2.49 GeV Gupta-Johnson (95)2.38 GeV Zeng et. al. (95)2.38 GeV

11/18/03Jianchun (JC) Wang13 How Does Potential Model Work on D Mesons? JPJP m(GeV)  (MeV) Decays to Expected m(GeV)    DD  DD  D*   D*   D ,D*  DiPierro & Eichten PRD64 (2001) Predictions

11/18/03Jianchun (JC) Wang14 Potential Model Calculation

11/18/03Jianchun (JC) Wang15 Prediction on Masses of D sJ Mesons  Potential models predict the mass and width of charm mesons (e.g. DiPierro & Eichten ), which worked quite well with D and D sJ 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

11/18/03Jianchun (JC) Wang16 D S  0 structure at 2317 MeV, ~ 40 MeV below DK threshold. “… This result will send theorists back to their drawing boards.”

The Experiments Involved

11/18/03Jianchun (JC) Wang18 ee ee e + e   (4S)  BB  hadrons How Particles are Produced? ee ee ee ee ee ee  e  e   qq  hadrons ee ee  (e + e   (4S)  BB) ~ 1 nb  (e + e    qq) ~ 3 nb  (e + e    cc) ~1.3 nb M(e + e   (GeV)

11/18/03Jianchun (JC) Wang19 The BaBar Experiment Asymmetric collider: 9.0GeV e  + 3.1GeV e +. Bunch crossing rate: ~ 4.2 ns. L = (6.6  ) cm  s   L dt = 91 fb  1 used ~100 million cc produced

11/18/03Jianchun (JC) Wang20 The Belle Experiment KLM CsI PID SVD TOF ee e+e+ CDC 1.5T Magnet Asymmetric collider: 8.0GeV e  + 3.5GeV e +. Bunch crossing rate: ~ 2.0 ns. L = (1.06  ) cm  s   L dt = 87 fb  1 used

11/18/03Jianchun (JC) Wang21 The CLEO II Experiment Symmetric collider: 5.29 GeV e  GeV e +. Bunch crossing space: ~ 14 ns. L = (1.25  ) cm  s   L dt = 13.5 fb  1 used

11/18/03Jianchun (JC) Wang22 The CDF Experiment L = (5  ) cm  s   L dt = 300 pb  1 used  c ~ 400  b (central) Symmetric pp collider: 980 GeV p GeV p. Bunch crossing rate: ~ 396 ns.

Discovery of Two New States

11/18/03Jianchun (JC) Wang24 M(D S   0 ) [GeV] BaBar Discovered D S (2317) The angular distribution is flat. As the final state is 0  0 , the resonance is possibly J P =0 + (0 +,1 ,2 + ). Could it be the missing 0 + D sJ state or just a reflection? M(D S   0 ) [GeV] D S +  +,K* 0 K   K + K   + N = 1267  53 M = (  0.4) MeV  = (8.6  0.4) MeV P(D S  0 ) > 3.5 GeV. D S +  +  0  K + K   +  0

11/18/03Jianchun (JC) Wang25 M (D S +    [GeV] Could The Resonance Be Real? DS*+DS*+ Reflections? “This mass corresponds to the overlap region of the D S *  D S  and D S (2317)  D S  0 signal bands that, because of the small width of both mesons, produces a narrow peak in the D S    mass distribution that survives a D S * 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.

11/18/03Jianchun (JC) Wang26 CLEO Confirmed D S (2317)  M> = (349.4  1.0) MeV  = (8.0  1.3) MeV P(D S  0 ) > 3.5 GeV DS*DS* CLEO quickly confirmed the narrow resonance at 2317 MeV. They noticed a slightly broader width than detector resolution (6 MeV).

11/18/03Jianchun (JC) Wang27  10  M> = (349.8  1.3) MeV  = (6.1  1.0) MeV P(D S *  0 ) > 3.5 GeV CLEO Discovered D S (2460)  CLEO observed a significant peak in D S *  0 spectrum at ~2.46 GeV.  Could it be the missing 1 + D sJ meson, or purely a reflection (feed-up) of D S (2317)? M(D S   )  M(D S  ) [GeV] Events / 5 MeV

11/18/03Jianchun (JC) Wang28 How Does Feed-up Happen? 2317 00 DSDS  Fake D S * Fake 2460 The feed-up peak has two interesting features distinct from the real signal peak. 1.If we consider the mass of D S * be shifted, it should not affect the feed-up peak other than a little shift. 2.The extra  results in smearing of the peak.

11/18/03Jianchun (JC) Wang29  D S  0 Scatter Plot D S (2460)  D S  0 MC D S (2317)  D S  0 MC

11/18/03Jianchun (JC) Wang30 D S * sideband D S * signal N = 55  10 !? D S * Sideband Spectrum There is a small enhancement in the normalized spectrum of D S * sidebands; But it accounts for only ~20% of the signal.

11/18/03Jianchun (JC) Wang31 Significance of D S (2460) Signal N = 42.4 ± 9.7 = (351.2 ± 1.7 ± 1.0) MeV  = (5.3 ± 1.1) MeV Significance = 5.7  M = (2463.6±2.1) MeV Function in the fit Gaussian function + 2 nd polynomial function + D S * sideband spectrum

11/18/03Jianchun (JC) Wang32 D S  0 Monte Carlo Simulations D S (2460)  D S *  0 signal MC  = 6.6  0.5 MeV D S (2317) does “feed up” to the D S (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. D S (2317)  D S  0 signal + random   = 14.9  0.6 MeV Much wider than 6.1±1.0 MeV

11/18/03Jianchun (JC) Wang33 Feed-down Also Happens 2460 00 DS*DS* Fake 2317 The absence of the soft  results in smearing of the peak.  DSDS

11/18/03Jianchun (JC) Wang34 D S  0 Monte Carlo Simulation D S (2317)  D s  0 signal MC  = 6.0  0.3 MeV D S (2460)  D S *  0 signal with photon skipped  = 14.9  0.4 MeV D S (2460) also “feed down” to D S (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.

11/18/03Jianchun (JC) Wang35 Cross-feed of Two D sJ Mesons CLEO dataMC: D S (2317)  D S  0 MC: D S (2460)  D S  0 Reconstruct as D S  0  =8.0±1.3 MeV N=190±19  =6.0±0.3 MeV Eff.  1 =  % Neglect the   =14.9±0.4 MeV  =0.84  0 (  =8.0) Reconstruct as D S *  0  =6.1±1.0 MeV N=55±10 Pick up a random   =14.9±0.6 MeV  =0.09  1 (  =6.1)  =6.6±0.5 MeV Eff.  0 =  % D S (2317) signal = 155  23 (+ ~18% feed-down)  consistent with double Gaussians fit. D S (2460) signal = 41  12 (+ ~25% feed-up)  consistent with fit to sideband subtracted spectrum.

11/18/03Jianchun (JC) Wang36 Double Gaussian Fit  Fit the spectrum with double Gaussian functions for the peak. Narrow Width Broad width Single Gaussian Data 6.0    1.3 MC 6.0   0.4 Events/5MeV/c 2  Determine the mass without the effect of reflection. = (350.0 ± 1.2 ± 1.0) MeV M = ( ± 1.7) MeV  The amount of reflection in the fit is consistent with calculation.

11/18/03Jianchun (JC) Wang37 Belle Confirmed Both States M(D S  0 )  M(D S ) (GeV) D S (2317) M(D S *  0 )  M(D S *) (GeV) D S (2460) ~30% of signals in the peak is due to feed-up from D S (2317).

11/18/03Jianchun (JC) Wang38 BaBar Confirmed D S (2460)  After careful study of the cross-feed, BaBar confirmed the existence of D S (2460).  Feedup rate at BaBar as a fraction of the 2460 signal size is ~50% compared with CLEO (~25%) & Belle (~30%). sideband background Fit to sideband subtracted data. Cross feed makes it difficult to measure the mass.  M=M(D S *  0 )  M(D S *) (GeV)

11/18/03Jianchun (JC) Wang39 Belle Observed D sJ in B Decays cos (helicity angle) D S (2460)  D S *  0 D S (2460)  D S  D S (2317)  D S  0

11/18/03Jianchun (JC) Wang40 Mass and Width of The New States  M 2317 –  M 2460 = 2.4 ± 1.0 MeV  D s (2460) < 5.5,  D s (2317) < 4.6 MeV 90% C.L. BaBar CLEO Belle (cont.) Belle (B) Average    1.0   2.1   1.6   1.2   0.5   0.6   1.7   0.4  0.8 M Ds(2317) –M Ds(1969) (MeV)M Ds(2460) –M Ds(2112) (MeV)

11/18/03Jianchun (JC) Wang41 Production of The New States  Production ratios of the two new states are consistent in different experiments  The production rates of D sJ produced in e  e   qq are for P>3.5 GeV. By CLEO  Production in B decays (by Belle).

Possible Explanations and Search of Other modes

11/18/03Jianchun (JC) Wang43 Possible Explanations  Barnes, Close & Lipkin: DK molecule. (hep-ph/ )  Szczepaniak: D  atom. (PLB 567 (2003),23)  Several authors: four quark particle. (Cheng & Hou, PLB 566(2003)193; Terasaki, PRD68(2003) ; Nussinov, hep-ph/ )  Van Beveran & Rupp: use a unitarized meson model to explain the low mass as a kind of threshold effect. (hep-ph/ )  Cahn & Jackson: use non-relativistic vector and scalar exchange force. (hep-ph/ )  …… Several possible explanations appeared after the discovery, some are quite exotic.

11/18/03Jianchun (JC) Wang44 DK Molecule  Why DK molecule?  Since the decay products are D S  0, 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 D S (2460) and D S (2317).  Resonances f 0, a 0 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 D S  .  One can study in B decays the D + K  molecule which decays to K  K   +  +.  If it is normal cs meson, one expect that the width of mode D S *  to be  =2keV. If it measurement shows very much different, it got to be other things. c u u s

11/18/03Jianchun (JC) Wang45 Pentaquark State  + ExperimentModeMass (MeV)Width (MeV)Signif. LEPS at Spring-8, JapanKnKn 1540  10 <  DIANA at ITEPKpKp 1539  2 < 9  CLAS at JLABKnKn 1542  5 21 (resolution)  SAPHIR at ELSAKnKn 1540  4  2 < 25  LEPS n  K─K─ K+K+ n ++ pp d u s d u

11/18/03Jianchun (JC) Wang46 Search For D S ( * )    Upper limits from CLEO: No narrow structures  I=0 for D S (2317), and D S (2460) Narrow structures in D S ( * )    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.

11/18/03Jianchun (JC) Wang47 Another Possible Explanation  D S (2317) and D S (2460) fit in well the quark model as ordinary 0 + and 1 + D sJ mesons except for maybe the masses (~ MeV below the expectation).  Bardeen, Eichten & Hill (hep-ph/ ) couple chiral perturbation theory with a quark model representing HQET. They infer that the D S (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.  D S (2317) and D S (2460) are below DK and D*K thresholds. The strong channel to D S  0 and D S *  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.

11/18/03Jianchun (JC) Wang48 Extra On BEH Model D(0 + )  D and D(1 + )  D(0 + ) are large may be due to large width ~300 MeV.

11/18/03Jianchun (JC) Wang49 Extra On BEH Model

11/18/03Jianchun (JC) Wang50 Belle Search for D s      Mode D s (2317) D s (2460) CLEO CDF Existence of D s      would  rule out J P =0 + possibility. D s1 (2536) N= 56  13 D s (2460) N= 60  12 Belle observed D s (2460)  D s    . No D s (2317)  D s      is observed.

11/18/03Jianchun (JC) Wang51 D s (2317) D s (2460) CLEO Search for D s  Mode Belle No D s (2460)  D s  is observed. Belle observed D s (2460)  D s  in both B decay and continuum and samples. D s  mode is forbidden J P =0 +. BaBar M(D S  ) GeV/c 2

11/18/03Jianchun (JC) Wang52 Search for D s   and  D s (2317)  Modes D s (2460) CLEO D s (2317)D s (2460) CLEO D s   mode is allowed for both J P =0 + and 1 +. D s (2317)  is allowed for J P =1 +. Absence of the mode indicates that the EM decay mechanism can not compete with D S *  0 which might be a strong but isospin violating process.

11/18/03Jianchun (JC) Wang53 Summary of Search for Other Modes Decay ChannelPossible J P Rule out J P Branching fraction ratio/Limit (90% CL)BEH prediction BaBarBelleCDFCLEO D s (2317) D s  0              D s             Not seen <4  Not seen< Ds Ds       Not seen  D s  0       Not seen  D s     Not seen<0.18  D s (2460) D s  0                D s     Not seen<0.31  Ds Ds          Not seen< 0.21Not seen0 D s           ? 0.14  Not seen< Ds Ds     Not seen 0.55   )  D s (2317)       BEH’s chiral symmetry + HQET model prediction is consistent with measurements.

11/18/03Jianchun (JC) Wang54 Factorization Mystery  Four-quark state or molecule would have B consistent with measurement. (Chen & Li hep-ph/ ; Datta & O’donnel hep-ph/ ; Cheng & Hou hep-ph/ )  Factorization implies the branching fractions be similar to B  DD S. The measurements are a factor of ~10 lower than expectations.

11/18/03Jianchun (JC) Wang55 Summary  Two new states are discovered at ~2.32 GeV in D S  0 mode and ~2.46 GeV in D S *  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 + D sJ states. Other explanations like molecule are not ruled out.  More experimental measurements and theoretical ideas are needed to reveal their true identities. c u u s c s

11/18/03Jianchun (JC) Wang56 Backup slides

11/18/03Jianchun (JC) Wang57 The Charm Mesons 

11/18/03Jianchun (JC) Wang58 BaBar Presentation at FPCP 2003

11/18/03Jianchun (JC) Wang59 CLEO Numbers in Continuum Data D S (2317)  D S  0 MCD S (2460)  D S  0 MC Reconstruct as D S  0  =6.0±0.3,  1 =  %  =14.9±0.4,  =0.84  0 Reconstruct as D S *  0  =14.9±0.6,  =0.09  1  =6.6±0.5,  0 =  % D S (2317)  D S  0 N=165  20 (190  19),  M=349.4  1.0,  =8.0  1.3/1.1 D S (2460)  D S *  0 N=55  10,  M=349.8  1.3,  =6.1  Solve cross feed: f 0 =0.091   0.015, f 1 =0.84  0.04  0.10 D S (2317)  D S  0 N=155  23 D S (2460)  D S *  0 N=41  sideband subtraction, D S (2460)  D S *  0 N=45.7  11.6,  M=351.2  1.7  1.0,  <7 -- two gaussians fit, D S (2317)  D S  0  M=350.0  1.2  1.0,  =6.0  1.2,  <7 Feed down  M=344.9  6.1,  =16.5  6.3  (  M) =1.2  Production of DsJ for P>3.5 over Ds production D S (2460)  D S *  0 rate = (3.5  0.9  0.2)  10  D S (2317)  D S  0 rate = (7.9  1.2  0.4)  10  D S *(2112)  D S  rate = 0.59  0.03  0.01

11/18/03Jianchun (JC) Wang60 BaBar Numbers in Continuum Data D S (2317)  D S  0 MCD S (2460)  D S  0 MC Reconstruct as D S  0  =7.5±0.3 == Reconstruct as D S *  0  ~ 15 MeV == D S (2317)  D S  0 N=1267  53, M=  0.4  3.0,  =8.6  0.4,  intrinsic <10, D S (2317)  D S  0 (other D S mode) N=273  33, M=  1.3,  =8.6  D S (2460)  D S *  0  M=346.2  0.9, sideband subtraction -- Unbinned likelihood fit to M(D S  0  D S  0 ),M(D S   D S (2460)  D S *  0 N=195  26, M=  1.0  1.0,  =8.5  1.0,  <10, angular disfavor 0-  M=345.6  1.0  1.0 D S (2460)  D S (2317)  N=0  23 ratio < 0.22 (95% CL) -- Take into account the contribution of Ds(2460) from MC. D S (2317)  D S  0 N=1020  50, M=  0.4  0.8,  =7.3  0.2 =>  M=348.8  0.4  0.8  *Br(2460)/  *Br (2317) = 0.25  0.03  0.03

11/18/03Jianchun (JC) Wang61 Belle Numbers in Continuum Data D S (2317)  D S  0 MCD S (2460)  D S  0 MC Reconstruct as D S  0  =7.1±0.2  =14.9±0.8,  M)=  Reconstruct as D S *  0  =12.3±1.8,  M)=8.0  3.8  =6.0±0.2,   =19.5±3.6 D S (2460)  D S *  0 N=126  25, M=  1.3  1.3,  M=344.1  1.3  1.1,  =5.8  1.3, sideband subtraction,  intrinsic <5.5 D S (2317)  D S  0 N=761  44  30, M=  0.5  0.9,  M=348.7  0.5  0.9,  =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  0.03 D S (2460)  D S  0 N=22  22, ratio<0.21 D S (2460)  D S  N=152  18, M=  1.3  2.0,  M=491.0  1.3  1.9, ratio=0.55  0.13  gaussian fit =>  M=347.1  1.3  1.9 D S (2317)  D S  ratio<0.05 D S (2317)  D S *  ratio<0.18 D S (2460)  D S *  ratio<0.31 D S (2460)  D S  N=59.7  11.5, M=  0.9  1.6,  M=491.4  0.9  1.5, ratio=0.14  0.04  0.02 =>  M=347.5  1.3  1.9 D S (2317)  D S  ratio< 4x10 -3

11/18/03Jianchun (JC) Wang62 Belle Numbers in B Decays D S (2460)  D S *  0, D S  M=  1.6  2.0 =>  M=346.8  1.6  2.0 D S (2317)  D S  0 M=  2.1  2.0 =>  M=351.3  2.1  2.0 D S (2460)  D S  helicity fit  2 /ndof = 5/6 for J=1, 44/6 for J=2. D S (2460)  D S  ratio=0.38  0.11  0.04