Evidence for the  c Sookyung Choi Gyeongsang University & Stephen L. Olsen University of Hawaii ‘

Expected mass of the  c ‘  c0,1,2 J/  ’’ cc cc ‘  =117 MeV  ’=??? potential model:  expect M(  c ’)  3.62~3.64 GeV cc level diagram: 3 D c1 ?? 3 D c2 3 D c3 1h1?1h1? close to the  ’

Expected widths/decay modes Similar to  c narrow (but not like the J/  ) 10<  < 20~30 MeV ~same decay channels Search in a channel with strong  c signal but absent in  ’ decays

Search in  c ’  K S K ±   channel Br(  c  K 0 K    ) is respectable (  2%) all charged particles (  (  E)  13 MeV) low combinatoric background no  ’ background (Br(  ’  K 0 K    )<10  4 –Br(  ’  K 0 K  )<Br(J/   K 0 K  )/30

Event selection Skim Hadron B: –R 2 <0.35 –  2chrgd K’s;  1chrgd  ;  1K S –M bc >5.2 GeV; |  E|<0.2 GeV –|cos  thrust | < 0.9  between B and rest of evnt –all candidate tracks constrained to IP Use expts 7 thru 13; b _0725 library

Charged kaon selection K/  id: atcpid(3,1,5)>0.6 p/K  id: atcpid(3,1,5)<0.95  veto:  _likelihood < 0.9 e veto: eid_prob(3,-1,5)<0.9 CDC hits: N ax  8 ; N ster  3 vertex :  r<0.3 ; |  z|<2.2

Charged pion selection K/  id: atcpid(3,1,5)<0.4 p/  id: atcpid(3,1,5)<0.9 e veto: eid_prob(3,-1,5)<0.95 CDC hits: N ax  8 ; N ster  3 vertex :  r<0.3 ; |  z|<2.2

K S     selection flight-length > 0.3 |  | <0.2 |M  – M Ks |< 12 MeV if both trks have SVD hits: –Z dist <1.2 otherwise: – Z dist ; |  |<0.1

continuum-bkgd suppression Fisher –5 SFW moments –cos  thrust –  p t |  particles with  thrust >60 o cos  B  B candidate production angle L = PDF( fisher ) x PDF(cos  B )

Fisher use: R 2,4 & R 2,3,4 majorminor SFW maj cos  thrust  p t |

Likelihood Ratio LR = L sig /(L sig + L qq ) Fisher cos  B cut

K* and charm veto 0   1 –  0  suppressed by an angular  c   momentum barrier backgrounds commonly have K*’s  veto events with K*: |M K  – M K* |>50 MeV also veto events with charm: |M K  – M D |>10 MeV | M KKs – M Ds |>10 MeV

Look at K K s K    combinations Select events in the  E M bc signal box

M(K S K    ) for signal-box evts M = 3653 ± 9 MeV  = MeV  = 3.8  “  c ’ ” properties (B +  K  K S K    + B 0  K S K S K    combined) 1.5-entries/evnt2-entries/evnt NB: N(  ’   S  <N(J/    S  )/30  1evt 38 evts100 evts 28 evts ? -??

Do slice fits: 3.55 GeV 3.60 GeV 3.65 GeV 3.70 GeV 3.75 GeV 6±4 evts 4 ± 4 evts 16± 5 evts 13± 4 evts 26±6 evts (  =5.2  )

Slice fit results M( K s K     N evts  ± ±4.4 ~3  ±  ±5.4 ~3  ±4.1~ BW with M =3653 &  = 30 MeV; not a fit! Poor agreement maybe due to the coarseness (50MeV) of the slice-fit bins

Summary We observe a 5.2  signal for B  K K S K    near 3650 MeV. This cannot be the  ’ Most likely this is B  K  c ’ with: –M  c’ = 3653 ± 9 MeV –   c’ = MeV This disagrees with the Crystal-Ball result M  c’ =3594±5 MeV but agrees with potential models.  ?? M bc 3625<M KSK  <3675 MeV