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2003-14 Powered By Docstoc
					Observation in BaBar of a narrow
resonance in the D+s p0 system at
           2317 MeV
           Roger Barlow
      Manchester University
    For the BABAR Collaboration
                                                   Data

•   1999-2002
•   91 fb-1
•   On and off (4S)
•   Search for D+s and p0 :
    Require
    – 3 tracks
    – 2 photons over 100 MeV
    – FW moments H2/H0 <0.9
                   Roger Barlow: FPCP Paris 2003          Slide 2
                                    p0 selection
• Both Eg > 100 MeV
• p0 fit probability
  >1%
• Neither g shared
  with another p0
  candidate

  Peak and sidebands

                Roger Barlow: FPCP Paris 2003   Slide 3
                                           
                                    D      s     selection(1)

                 Kp
                   
  D s
        K
                                                      D+s
• Kaon id from DIRC                              D+
  & dE/dx via Neural                                        D*+
  network
• Vertex fit P>0.1%
Peaks from
• D+(1869)
• D+s(1970)
• D*+(2010)D0p+
                      Roger Barlow: FPCP Paris 2003           Slide 4
                                          
                                   D      s selection(2)
• M(K+K-)<1.84 GeV
• M(K+K-)M() or                                    D+s
      M(Kp)M(K*)
•  or K* decays with
  |Cos h|>0.5                               D+
• p*(K+K- p+ p0)>2.5 GeV

    Signal and sidebands
                    shown
  80K D+s in signal region

                     Roger Barlow: FPCP Paris 2003         Slide 5
                                            The signal
Large (unexpected)
  peak in D+sp0 mass                                    ?
                                                      D+sJ(2317)
  at 2.32 GeV

Named as D*sJ(2317)+

Small spike from D*+s just on
  kinematic limit


                      Roger Barlow: FPCP Paris 2003                Slide 6
                               Check# 1
                               Monte Carlo
Reproduces D+s but no D*sJ(2317)+


                       D+s
          D+




               Roger Barlow: FPCP Paris 2003   Slide 7
                              Check# 2
                              Sidebands
M(K+K- p+ p0) from sidebands in yellow
  D+s sidebands
                                              p0 sidebands




No signal present
              Roger Barlow: FPCP Paris 2003             Slide 8
                             Check# 3
                             Different D+s
                             decays
Seen in both D+s  p
 and D+s K*K                                D+sJ(2317)




Also in D+s K+K-pp0
    at the same mass



             Roger Barlow: FPCP Paris 2003            Slide 9
                                 Check# 4
                                 Reflections
• Particle ID?
  – Take events: reassign K as p.
  – No sign of D+ or D0 or D*


• D*+s(2112) D+sg + extra g?
        No: Antiselecting M(D+sg 2112)
                enhances peak at 2317
                 Roger Barlow: FPCP Paris 2003   Slide 10
                                           Properties#1
                                           p* dependence
Signal enhanced at
  high p*

As expected from
  e+ecc production



(Momentum of D*+sJ(2317)
  in CMS)

                           Roger Barlow: FPCP Paris 2003   Slide 11
                                Properties#2
                                Mass
• Take p*>3.5 GeV
• Gaussian +
  polynomial
• Peak at 2316.80.4
  MeV
• 126753 signal
  events
• Systematic
  uncertainty below
  3 MeV
                Roger Barlow: FPCP Paris 2003   Slide 12
                                  Properties#3
                                     Width
• Single Gaussian
• Standard Deviation
  8.60.4 MeV
• MC (revised) predicts
  7.50.3 MeV
• Measurement of
  D+sK+K-p+p0 gives 6.7
  0.1 MeV
• Observed width
  compatible with our mass
  resolution
               10 MeV
                  Roger Barlow: FPCP Paris 2003   Slide 13
                                   Properties#4
                                   Angular
                                   Distribution
• Plot helicity
  angle of p0 in
  D*+sJ(2317)
  frame
• Correct for
  efficiency     Consistent with being flat:
                       Suggests J=0. (Or unpolarised
                                    and J=anything)
                   Roger Barlow: FPCP Paris 2003   Slide 14
                                   Properties#5
                                   Other modes
Not seen in
  –   D+s g
  –   D*+s (2112) g                D*+s(2112)



  –   D+s g g
  –   D+s p0g
  –   D+s p0p0



                      Roger Barlow: FPCP Paris 2003   Slide 15
                                         Comment on
                                           Ds
                                            + p0g
• No peak at 2317
• But new peak appears
  at 2460
• Enhanced when
  M(D+sg)2112=M(D*+s)

             2317


   M(Dsg)
                            Care needed!
  2112
                            Peaks at Dsp0 (2317) and Dsg(2112)
                              combine to give reflection with
            M(Dsp0)           M(Dsp0g )2460
                      Roger Barlow: FPCP Paris 2003   Slide 16
                                     D*+sJ(2317)
                                    Interpretation
A cs state: D*s
Below threshold for DK, D*K
Dsp decay violates isospin, hence narrow
Parity conservation  JP=0+, 1-,2+…
                  0+ plausible from Cos  distribution
L=1 orbital excitation.
But other L=1 states (1+ and 2+) are at 2536, 2573
Qq potential models predict 0+ at M=2480
                     2317 << 2480
Either re-think theory or include unorthodox state
                   Roger Barlow: FPCP Paris 2003   Slide 17
                              Confirmation
Confirmed by CLEO and BELLE
Mass and width and decay modes
 consistent.

CLEO also claim D*+s(2463) in
 D*+s(2112) p0


             Roger Barlow: FPCP Paris 2003   Slide 18
                                             The Peak in
                                               D* s
                                                  + p0

BaBar                                    CLEO
• There is a peak at 2.46 GeV            • There is a peak at 2.463
• Some of it is a reflection of            GeV
  the 2317. How much is still            • Some, but not all of it, is
  under study. Great care is
  required.                                a reflection of the 2317
• Even if this peak is a                 • Some of the 2317 is a
  resonance, it cannot account             reflection of the 2463
  for all the 2317 signal

      If it exists, careful extraction of yields, masses and widths is
                        needed. Work in progress…
                         Roger Barlow: FPCP Paris 2003         Slide 19
                                 Conclusions
• BaBar has observed an unexpected
  narrow resonance: the D*+sJ(2317)
• Decays to D+sp0
• Spin-parity compatible with 0+
• Confirmed by CLEO and BELLE



             Roger Barlow: FPCP Paris 2003   Slide 20

				
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