Discovery of D sJ (2463) + (part II) JC Wang CLEO Meeting 06/20/03 Authors Dave Cinabro Selina Li Sheldon Stone Jon Urheim Jianchun Wang Committees Roy Briere (chair) David Miller David Besson John Yelton  900

06/20/03Jianchun (JC) Wang2 BaBar Discovery  BaBar observed a narrow D s  0 resonance at GeV, possibly a J P = 0 + state (hep-ex/ ). They reconstructed 1267  53 events, with P(D s  0 ) > 3.5 GeV using 91 fb  data. M( D s   0 ) BaBar M( D s   0 )  They also noticed a peak at 2.46 GeV. “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”. Reflections?

06/20/03Jianchun (JC) Wang3 Possible Explanations  Four D s **(L=1) states: J P = 0 +, 1 +, 1 + & 2 +. One 1 + & 2 + seen. Others are predicted to be above DK threshold and have large ~200 MeV widths. This state is way below DK threshold.  The D s  o decays from an initial cs state violates iso-spin conservation. Hence the decay is suppressed and the decay width is narrow. So the low mass ensures the narrow width.  Bardeen, Eichten and Hill (hep-ph/ ) couple chiral perturbation theory with a quark model representing HQET. They infer that D s *(2317) is the 0 + state. The theory also predict the existence of the 1 + partner of this state, and has mass splitting identical to that of D s *(2112) and D s ( M(1 + )  M(0 + ) = M(1  )  M(0  ) ). The branching fraction of other possible modes are also calculated.  Many other theoretical explanations appeared (see references in the paper): For example, it could be a D  / DK molecule (see Adam Szczepaniak’s talk).

06/20/03Jianchun (JC) Wang4 The D s  0 Final State Fit result N = 165  20  = 8.0  1.3 MeV  M> =  1.0 MeV Brief selection criteria  All CLEO II and II.V data  P(D s  0 ) > 3.5 GeV  D s   ,   K  K   |cos   | > 0.3  Invariant mass cuts ~ 2.5   Photons in good barrel. Ds*Ds*

06/20/03Jianchun (JC) Wang5 The D s *  0 Final State Fit result N = 55.3  10.1  = 6.1  1.0 MeV  M> =  1.3 MeV Brief selection criteria  All CLEO II and II.V data  P(D s *  0 ) > 3.5 GeV  D s   ,   K  K   |cos   | > 0.3  Invariant mass cuts ~ 2.5   Photons in good barrel. D s * sideband D s * signal !?

06/20/03Jianchun (JC) Wang6  D s  0 Scatter Plot

06/20/03Jianchun (JC) Wang7 D s  0 Monte Carlo Simulations D s (2463)  D s *  0 signal MC  = 6.5  0.2 MeV D s (2317) does “feed up” to the D s (2463) 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 6.5. D s (2317)  D s  0 signal + random   = 14.9  0.6 MeV Much wider than 6.1±1.0 MeV

06/20/03Jianchun (JC) Wang8 Feed Down: D s (2463) Candidates Reconstructed as D s (2317) All events in the D s *  0 mass spectrum are used to show the D s (2463) signal “feed down” to the D s (2317) spectrum.

06/20/03Jianchun (JC) Wang9 Reconstruct D s  0 from MC D s (2317)  D s  0 signal MC  = 6.5  0.3 MeV D s (2463)  D s *  0 signal with photon skipped  = 14.9  0.4 MeV D s (2463) 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 6.5 MeV.

06/20/03Jianchun (JC) Wang10 Yield Unfolding R0  reconstructed D sJ (2317)  D s  0 excluding feed-down. R1  reconstructed D sJ (2463)  D s *  0 excluding feed-up. N0 = R0 + feed-down = R0 + R1  f1 N1 = R1 + feed-up = R1 + R0  f0 R0 =  23.4 R1 = 41.2  11.5 f   feed-up probability relative to true D s  0 yield. (0.091±0.007±0.015) f  feed-down probability relative to true D s *  0 yield. (0.84±0.04±0.10) N0  number of events extracted from fit to D s  0 mass spectrum. (189.5  18.9) N1  number of events extracted from fit to D s *  0 mass spectrum. (55.3  10.1)

06/20/03Jianchun (JC) Wang11 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.

06/20/03Jianchun (JC) Wang12 Sideband Subtraction Sideband subtraction Unfolding method Number of events45.7 ± ± 11.1 M(D s *  0 )  M(D s *) in MeV ± ± 1.3 Signal width (  ) in MeV 5.5 ± ± 1.0 = (351.2 ± 1.7 ± 1.0) MeV M = ± 2.1 MeV

06/20/03Jianchun (JC) Wang13 Significance of D s (2463) Signal  Fit the spectrum with:  Single Gaussian for true signal.  Sideband spectrum for feedup and part of combinatorial bkg.  2 nd order polynomial for bkg.  We can get the significance of signal: sqrt( 32.4) = 5.7  Number of true signals: 42.4  9.7

06/20/03Jianchun (JC) Wang14 Production Rate of D sJ Mesons Yield (P>3.5) Efficiency (%) Production Ratio D s (2463)  D s     (D s  )     D s (2317)  D s     D s   D s   D s (1969)   The final D sJ candidates are required to be P>3.5 GeV.  D s is reconstructed in D s   ,   K  K   mode. The efficiency is the value in the table times BR of the decay chain listed.

06/20/03Jianchun (JC) Wang15 Kinematically Allowed D sJ Decay Channels Decay ChannelSpin parityPossible J P of D sJ D s (2317) D s  0         D s            , OZI suppressed Ds Ds       D s   0       D s          D s (2463) D s   0             D s                      OZI suppressed D s              Ds 0Ds 0       D s                    OZI suppressed Ds Ds             D s (2317)  0         D s (2317)        

06/20/03Jianchun (JC) Wang16 Search For D s  and D s   Decay odes N(2317) =  N(2463) =  D s (2317)D s (2463) N(2317) =  N(2463) =  D s (2317) D s (2463)

06/20/03Jianchun (JC) Wang17 Search For D s      and D s (2317)  Decay Modes D s (2317) D s (2463) N(2317) =  N(2463) =  D s (2463) N(2463) =  D s (2463)  D s (2317)  (D s  0 )  has reflection from mode D s (2463)  D s *  0  (D s  )  0

06/20/03Jianchun (JC) Wang18 The 90% C.L. Upper Limits Decay ChannelYieldEfficiency (%) Ratio (90% C.L.) Prediction D s (2317) D s  0  0.6  D s      2.3  0.8  Ds Ds  13  0.1  D s   0  3.9  0.3  D s   5.2  0.5  Ds(2463) D s   0  12  0.2  D s   7.7  0.3  D s      5.4  1.5  Ds Ds  17  0.4  D s (2317)  3.0  0.1 

06/20/03Jianchun (JC) Wang19 Nature of D s (2317) and D s (2463)  D s (2317) and D s (2463) fit in well the quark model as 0 + and 1 + cs mesons except for maybe the mass.  Chiral perturbation + HQET  lower mass.  D s (2317) is below DK threshold. D s (2463) is below D*K threshold and above DK, which is suppressed (1 +     ).  The measurements also back up chiral perturbation + HQET model.  It is nature to think that they are 0 + and 1 + D s states. D s (2463)  D s   0 = (351.2 ± 1.7 ± 1.0) MeV M = ± 2.1 MeV Width < 7.0 MeV at 90% C.L. D s (2317)  D s  0 = (350.0 ± 1.2 ± 1.0) MeV M = ± 1.7 MeV Width < 7.0 MeV at 90% C.L.

06/20/03Jianchun (JC) Wang20 Search For D s +   and D s  +   Modes D s (2317) D s (2463) D s (2317) D s (2463) Resonant D s +   or D s  +   surely will be interesting for other models (e.g. D  atom)

06/20/03Jianchun (JC) Wang21 Summary  Confirmed D sJ (2317):  Mass =  1.7 MeV/c 2, = (350.0 ± 1.2 ± 1.0) MeV  Very narrow intrinsic width.  Decaying to D s  0, as expected for J P = 0 +.  Observed a new state D sJ (2463):  Mass =  2.1 MeV, = (351.6  1.2  1.0) MeV.  Very narrow intrinsic width.  Decaying to D s *  0, as expected for J P = 1 +.  The results are compatible with model (Chiral perturbation+HQET) predictions of 0 + and 1 + D s states, and mass splitting.  Obtained upper limits of branching fraction for the other decay modes relative to the observed states.  Submitted to PRD (hep-ex/ ).