Stephen L. Olsen Univ. of Hawaii A narrow pp enhancement near M pp  2m p in J/    pp BES Representing: Beijing, China

NN bound states (baryonium)?? + n+  deuteron: loosely bound 3-q 3-q color singlets with M d = 2m p -  baryonium: loosely bound 3-q 3-q color singlets with M b = 2m p -  ? attractive nuclear force attractive force?? There is lots & lots of literature about this possibility

pp  e + e  Bardin etal e + e   hadrons FENICE e+e6e+e6 2m p Fit: M = 1870 ± 10 MeV  = 10 ± 5 MeV R. Calabrese PEP-N work-shop proceedings DM2 unpub. Is there a narrow J PC =1  pp system near M pp = 2m p ?

pd  5  + p s at rest P ps (MeV) S.Ahmad, et al ASTERIX Collab. O.D.Dalkarov et al, PLB392, 229 (1996) [also D.Bridges et al, PLB180, 313(1986)] spectator model M=1870,  =10 resonance included

study pp from J/    pp C-parity = + S (P?)-wave (for M pp  2m p )  probes J PC = 0  (0  ?)states complements pp  e  e  and e  e  annihilation unpolluted (by other hadrons) environment

The BES Detector TOF EM Shwr counter

Belle sees low-mass pp systems in B decays pp M M B  D 0 pp B  ppK

Use BESII’s 58M J/  decays J/    pp Select J/    pp 4-C kinematic fit dE/dx for proton id non-pp bkg small main bkg from J/     pp ???? J/    c  c   pp (calibration reaction)

Are these really p’s & p’s ? E BSC (p) p and p in signal region mostly stop in TOF counters in front of the BSC. The p does nothing; the p annihilates. E BSC (p) Annihilation products that are matched to the p track M(pp)<1.9 GeV

Study J/    0 pp bkg with MC & data J/    0 pp (data) three-body phase space Monte Carlo J/    0 pp   pp (MC) M(pp)-2m p (GeV) no peak!!

Fit signal with an S(P)-wave BW q = daughter momentum q 0 = daughter peak keep constant threshold factor

Fit to data M=1859 MeV/c 2  < 30 MeV/c 2 (90% CL) J/    pp M(pp)-2m p (GeV) body phase space acceptance  2 /dof=56/56 fitted peak location acceptance weighted BW  10  25

Is M peak really less than 2m p ? No turnover at threshold  peak mass must be <2m p weight events by q 0 /q: (i.e remove threshold factor) M(pp)-2m p (GeV)

P-wave fit?? M=1876 ± 3 MeV  < 30 MeV (90% CL)  2 /dof=59/56 OK! M=2m p

D-wave fit?? M=1885 ± ? MeV  < 30 MeV (90% CL)  2 /dof=1405/56 NG!!

cos   distribution 1+cos 2   (expected for J/     ) sin 2   M(pp)<1.9 GeV

mass determination bias threshold observed peak BW “peak” below-threshold mass & widths measurements can be biased when there is background

include possible biases as (asymmetric) statistical & systematic errors if what we see is an S-wave resonance: M=1859 MeV/c 2  < 30 MeV/c 2 (90% CL)  10  25

Summary a large enhancement seen near 2m p in the M pp distribution for J/    pp decays. not apparent in J/     pp decays not consistent with any PDG meson state S- or P-wave can fit data if it is an S-wave resonance: –M peak is below 2m p (M=1859 MeV/c 2 ) –full width is narrow (  <30 MeV/c 2 ) –dN/dcos   consistent with J PC = 0  or  0  Is this a scalar baryonium partner to the 1  – 1870 MeV state in e  e  and pd annihilations?  10  25

could it be a tail of a known resonance? 0  resonances in PDG tables:  (1760) M=1760  = 60 MeV  (1800) M=1801  = 210 MeV  2 /dof=323/58  2 /dof=412/58

Comments peak below, but near 2m p : baryonium? narrow width: why so long-lived? similar patterns seen in baryon-antibaryon systems produced in B meson decays –B  ppK B  ppD B  p  B  p  c 

Strange & charmed systems B   p   M(  p)  (GeV) BpcBpc M(  c  p)  (GeV) (in these cases, the peaking doesn’t seem to be right at threshold)

Coulomb effect? coulomb factor phase-space term

BW vs Coulomb

Systematic errors vary all procedures: fit results don’t change much  N evts