Zijin Guo Univ. of Hawaii Representing BES Collaboration J/ pp and BES Beijing, China
The BES Detector TOF EM Shwr counter
World J/ and (2S) Samples (10 6 ) J/ (2S)
A narrow pp enhancement near M pp 2m p in J/ pp
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+e6e+e6 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 ?
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
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)
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
P-wave fit?? M=1876 ± 3 MeV < 30 MeV (90% CL) 2 /dof=59/56 OK! M=2m p
cos distribution 1+cos 2 (expected for J/ ) sin 2 M(pp)<1.9 GeV
Summary (I) if what we see is an S-wave resonance: M=1859 MeV/c 2 < 30 MeV/c 2 (90% CL) 10 25 A narrow pp enhancement near M pp 2m p in J/ pp
not consistent with any PDG meson state 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) BpcBpc M( c p) (GeV) (in these cases, the peaking doesn’t seem to be right at threshold)
Partial Wave Analysis of J/ KK
Lattice QCD: the ground state scalar glueball should be in the mass range 1.5 – 1.7 GeV Long history of uncertainty about f 0 (1710) J / K + K - and K S K S are very important to investigate the f 0 (1710)
Data and Analysis Method Perform separate amplitude analyses for J/ K + K - K S K S Amplitudes are fit to relativistic covariant tensor expressions (mass range 1-2 GeV) The maximum likelihood method is employed Bin-by-bin fit: the data are analyzed independently in each mass bin (40MeV) Global fit: Breit-Wigner structures + mass, width scan + lnL comparison
The K + K - and K S K S mass distributions from J/ radiative decay after acceptance and isospin corrections
J/ f’ 2 (1525) f 0 (1710) f 2 (1270) f 0 (1500) +broad 0 ++ and 2 ++ Components used in the PWA fit
Bin-by-bin fit Global fit Amplitude intensity
Summary (II) Using BESII data, partial wave analyses were done on the K + K - and K S K S systems produced in J/ radiative decay for the mass range 1-2 GeV KK D- wave intensity shows a clear f’ 2 (1525) signal and the helicity amplitude ratios x,y appear to be consistent with the theoretical prediction
Strong production of f 0 (1710) M = 1740±4± 10 MeV Г = MeV (Global fit) The non-flat angular distribution in the KK mass region ~1.7 GeV is due to the interference between S- wave and weak D- wave amplitudes Bin-by-bin fit and global fit give very consistent analysis results
Results Bin-by-bin Global
Systematic Error global fit
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!!
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)
mass determination bias threshold observed peak BW “peak” below-threshold mass & widths measurements can be biased when there is background
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
Coulomb effect? coulomb factor phase-space term
BW vs Coulomb