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New Resonances at Belle
Jolanta Brodzicka INP Kraków,
for the Belle Collaboration
ICFP 2005
October 4th, 2005 Taiwan
Outline
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X(3872) properties
Y(3940), a hybrid state?
X(3940), a new charmonium state?
Z(3930), an excited charmonium state?
Summary
Intriguing X(3872)
 X(3872)+- J/ discovered by Belle in 2003 in B+K++- J/ decay
253fb-1
N=49.18.4
X+- J/
M= 3872.0 ± 0.6 ± 0.5 MeV
<2.3 MeV @90% C.L.
BF(BK X)BF( X+-J/)=1.31±0.24±0.13 10-5
M(+-J/)
 Confirmed by other experiments (BaBar, D0, CDF) and included in PDG2005
 M and  do not fit well any potential model charmonium states
 M(+-) peaks at kinematic limit ((770)-like)
X(3872) 0J/ is isospin violating decay
 MX ~ MD*0+ MD0  speculation that X might be a molecular D*0D0 bound state
 JPC= 1++ favored by some models
(Swanson, PLB 588, 189(2004))
 Expected admixture of (782)J/ and a small (770)J/ component
in addition to D*0D0
Jolanta Brodzicka, INP Kraków
New Resonances
ICFP 2005
Evidence for X(3872)  J/
 If X(3872)  J/  C=+1 for X(3872)
 search for BK X(3872), X(3872)  J/ decay
 Mbc distributions in M( J/) bins
 significant B signal only for M( J/)~MX(3872)
 Fit Mbc in M( J/) bins
 BK  J/ signal yield versus M( J/)
X(3872) region
N=13.6±4.4 (4.0)
M( J/)
 CX(3872) =+1 established
BF(BK X)BF(X J/)=1.8±0.6±0.110-6
(X J/)/(X+-J/) = 0.14±0.05
Jolanta Brodzicka, INP Kraków
New Resonances
ICFP 2005
X(3872)  J/ sub-threshold decay
Kinematical limit for X(3872) J/ is 7.5MeV below M  via virtual 
Search for BK X(3872), X(3872) J/, +-0 decay
 BK +-0 J/ candidates selected in E-Mbc signal region
X(3872) +-0 J/ selected:|M(3J/) – 3872|<16.5 MeV
 Mbcvs. E distributions fitted in bins of M(+-0 )
 B signal yield versus M(+-0 )
 Significant B signal only for (782) region M(+-0 )>750 MeV
 Background: 2.1±1.0 (from BK J/ and non-resonant BK +-0 J/)
Virtual (782)?
N=12.4±4.1 (4.3)
M(+-0 )
 Strong support for molecular D*0D0
interptetation
 Further evidence of C=+1 for X(3872)
BF(X +-0 J/)/BF( X +-J/) =1.0 ±0.4 ±0.3  large isospin violation!
Jolanta Brodzicka, INP Kraków
New Resonances
ICFP 2005
Fit to M(+-)
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Constraints on JPC of X(3872)
I
For C=+1 states +- J/ final state is primarily J/,
J++ :  and J/ in a relative S/D-wave; J-+ :  and J/ in a P-wave
M(+-) at kinematical limit is suppressed by (p*J/)2L+1
 shape of high-mass part of M(+-) provides some JPC information
S-wave
2/d.o.f=43/39
Favored by M(+-)
 PX(3872) =+1 is favored
P-wave
2/d.o.f=71/39
Disfavored
M(+-)
 X(3872) D0D00 observation
 BK D0D00 (K D0 D*0) candidates selected
using E-Mbc
 Enhancement in M(D0D00)MX observed
 It is difficult to distinguish D0D00 and D0 D*0
Preliminary
N=12.5±3.9
(>5)
BF(BK X)BF(XDD)=1.6±0.4±0.310-4
 XDD makes J2 unlikely,
for J=2 D-wave required, suppressed by (p*)5
Jolanta Brodzicka, INP Kraków
New Resonances
ICFP 2005
Constraints on JPC of X(3872)
II
Two-body decay BKX(3872)
 constraints on X spin and K-X relative angular momentum
 Full angular analysis limited by low statistic (NX50 events)
 Rosner’s coordinate system: x-axis is negative of K direction in X rest frame,
x-y plane defined by + and K, z-axis completes right handed system
Rosner PRD 70, 094023 (2004)
 Each JPC hypothesis is examined using most distinctive angular distribution
 0-+ hypothesis:  and J/ in a P-wave
 Predicted angular distribution: d2N/d(cos) d(cos)  sin2 sin2
(in the limit where X,  and J/ rest frames coincide)
2/d.o.f=18/9
MC
expectations
Poor fit to cos distribution  evidence against 0-+
Jolanta Brodzicka, INP Kraków
New Resonances
|cos|
2/d.o.f=34/9
|cos|
ICFP 2005
Constraints on JPC of X(3872)
III
 0++ hypothesis:  and J/ in relative S- or D-wave
(D-wave disfavored by M(+-) and suppressed by phase space)
 Predicted angular distribution: dN/d(cosl) sin2l
MC
expectation
2/d.o.f=31/9
Poor agreement
 0++ ruled out
|cosl|
1++ hypothesis:  and J/ in relative S-/D-wave
d2N/d(cosl) d(cos) sin2l sin2
2/d.o.f=11/9
|cosl|
2/d.o.f=5/9
Good agreement
for both distr.
1++ favored
|cos|
Jolanta Brodzicka, INP Kraków
New Resonances
ICFP 2005
Observation of Y(3940)   J/
 Discovery of X(3872) encouraged further studies of h+J/ systems
 BK  J/, +-0 candidates selected
 B signal yield determine in M(J/) bins
by performing fits to Mbc distributions
Strong near-threshold enhancement in M(J/) @ 3.94GeV
N=58±11 (8.1)
M= 3943±11±13 MeV
=87±22±26 MeV
BF(BK Y)BF(YJ/)=7.1 ±1.3 ±3.110-5
 Is Y(3940) threshold effect or new charmonium state?
 Charmonium meson with this mass would dominantly decay to DD(*)
 Y(3940) properties are similar to those predicted
for some of the cc-gluon hybrid states
Jolanta Brodzicka, INP Kraków
New Resonances
ICFP 2005
Observation of X(3940) in e+e-J/ X annihilation
 Double charmonium production in e+e- annihilation (J/ + c c ’c):
large cross sections, difficult to understand within NRQCD
 cc production in different processes not completely understood
 theoretical interest renewed
 Searching region extended above DD threshold with new data (350fb-1)
2
 Spectrum of a J/ recoil mass studied M recoil ( J / )  ( ECMS  E * J / ) 2  p* J /
 New peak observed in Mrecoil(J/) @ 3.94GeV =39±29MeV
Fit result:
X(3940)
c
BornBF( X(3940)>2 charged tracks )
=10.6±2.5±2.4 fb
Jolanta Brodzicka, INP Kraków
New Resonances
c
’c
DD threshold
ICFP 2005
Search for X(3940) D(*)D
 Full reconstruction of e+e- J/X, XD(*)D not practical
 To increase efficiency only one D reconstructed
 Spectrum of Mrecoil(J/D) is studied,
ND*D=55±18
other D(*) seen as peak in Mrecoil(J/D)
NDD=86±17
(D* and D well separated)
 Observed processes e+e- J/DD, J/DD*
 Mrecoil(J/D) refited to MD or MD*
to improve Mrecoil(J/) resolution
 Search for XD(*)D in Mrecoil(J/) M(D(*)D)
spectra
X(3940)D*D
N=24.5 ± 6.9 (5.0)
M=3943 ± 6 MeV
=15.4 ± 10 MeV
BF(X(3940)D*D) = 96
dominant decay mode
+45
-32
Jolanta Brodzicka, INP Kraków
±22 %
X(3940)DD
N=0.2 +4.4
<8.1
–3.5
BF(X(3940)DD) < 41% @90% C.L.
New Resonances
ICFP 2005
Are X(3940) and Y(3940) the same particle?
search for X(3940)  J/ 
J/  reconstructed from e+e- J/ J/  final state
M(J/ ) vs. Mrecoil(J/ ) studied to look for X(3940)
for
M (J/ ) – MX(3940)
< 40 MeV
Signal region for
e+e- J/ X(3940),
X(3940)  J/ 
NJ/= 2.2
+4.5
–3.7
NX = 1.9
+3.2 <
–2.4
7.4 @90% C.L.
BF( X(3940)J/ ) < 26% @90% C.L.
for Mrecoil (J/ ) – MJ/<100 MeV
Jolanta Brodzicka, INP Kraków
New Resonances
ICFP 2005
Observation of Z(3930) in   DD
 Motivation: study  production of high mass cc states decaying into DD
 Known radially excited 2S charmonium states ’ and ’c: M<MDD
 23PJ(’cJ) predicted to lie: 3.9-4.0 GeV and to decay mainly to DD
 Search for cc states produced via   DD process
by studying untagged mode e+e- e+e- DD
 Pt(DD)<0.05GeV in e+e- cms  it restricts  virtualities
and enhances exclusive   DD production
 New peak observed in M(DD)@ 3.93 GeV
 Pt(DD) distribution for Z(3930) region agrees with
MC for exclusive two-photon DD production
N=4111 (5.5)
M=393142 MeV
=2083 MeV
MC
expectation
(2J+1) BF (ZDD) =1.13±0.30±0.18 keV
Jolanta Brodzicka, INP Kraków
New Resonances
ICFP 2005
Z(3930) angular distribution
 Study of the angle of D relative to the beam axis in the  cms frame
 Events from the 3.93 GeV peak tend to
concentrate at small |cos * values
for 3.91< M(DD) <3.95 GeV/c2
Spin-2
dN/d(cos *)~sin4*
2/d.o.f=7/9
Spin-0
flat distr.
2/d.o.f=32/9
Data prefer a J=2 assignment
 Z(3930) is ’c2 the 23P2
charmonium state
Jolanta Brodzicka, INP Kraków
New Resonances
ICFP 2005
Summary
Belle found:
 More informations to explain X(3872) properties
 X(3872) quantum numbers: JPC=1++
 New charmonium state X(3940) (c(3S)?)
in double charmonium production
 Z(3930) in  process, Z(3930) = ’c2
Jolanta Brodzicka, INP Kraków
New Resonances
ICFP 2005