Transcript vepp06WS talk

New states in B decays
-with “hidden charm”2006 Mar. BINP  to  WS
Kenkichi Miyabayashi
Nara Women’s University
(for Belle collaboration)
Outline
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Introduction
B-meson/charmonium reconstruction
First sensation, discovery of X(3872)→ J/ +Second scoop, Y(3940)→ J/ 
X(3872) more decay modes, determination of JPC
Summary and prospect
Introduction
B decays as a source of
“hidden charm”(charm anti-charm )
Cabbibo-favored diagram (Vcb and Vcs)→ commonly produced!
B
“hidden
Spectroscopy
charm”
↓
Mass, Width?
New states?
Kaon
Reconstruction of charmonium
J/→di-lepton decays
are reconstructed as
a prominent peak.
In di-electron channel,
include photons detected
near electron/positron
tracks to recover Brems.
as much as possible
in order to reduce
radiative tail.
m+m-
e+e-
Reconstruction of charmonium(cont.)
(2S)
→ J/ +-
cc1, cc2 → J/ g
cc1
cc2
Higher charmonium states((2S), cc) are reconstructed using
mass difference.
Reconstruction of B decays
Example; B0→ J/ KS
Using Υ(4S)→ BB kinematics
DE(GeV)
Mbc = { (ECM/2)2 - (S Pi)2}1/2
Signal peaks at B mass
(5.28GeV)
DE = S Ei - ECM/2
Signal peaks at 0.
Mbc(GeV)
First sensation, peak at 3872 MeV in
“look-back” distribution
(2S)
“landmark”
•K +- J/ is combined to form a
B candidate.
•Using the B candidate’s daughter
particles, the mass difference
distribution is checked.
Narrow unknown peak is there,
above DD threshold!
Mll - Mll (GeV)
Belle, 152M BB,
PRL91,261801(2003)
Second scoop, B→ KJ/
enhancement; Y(3940)
Y(3940)
M=3943±11 MeV
=87±22 MeV
(stat. error only)
Mbc for each MJ/ bin
B signal yield as a func. of MJ/
Belle, 275M BB, PRL94,182002(2005)
X(3872)→ J/ 
A virtual ?
Signal yield as
a func. of M
Mbc in each MJ/ bin
Br(X3J/)
Br(X2J/)
12.4±4.2 events
Belle 275M BB,
hep-ex/0505037
= 1.0 ± 0.5 Large isospin(at least G-parity)
violation!!
X(3872)→ J/ g
B→ K g J/
candidates
13.6±4.4 events
(4 signif.)
cc1→ g J/
“landmark”
MJ/g (MeV)
Mbc in each MJ/g bin
Br(XgJ/)
Br(XJ/)
=0.14 ± 0.05
B signal yield as
a func. of MJ/g
Belle 275M BB
hep-ex/0505037
X(3872)’s
PC
J
C=+1 is established!
•X(3872)→ J/ g is only allowed for C=+1.
•X(3872)→ J/  supports this picture.
•X(3872)→ J/ , M looks like a 
Shape of M distribution favors S-wave btw J/ and
 (different centrifugal barrier for P, D-wave)→ P=+1!
X(3872)’s
PC
J
(cont.)
Angular distribution of X(3872)’s decay products
→ determination of spin.
J/
z
Jz=0
X3872
J=0
J=0
K

Rosner, PRD70,094023, Bugg, PRD71,016006,
Suzuki&Pakvasa, PLB579,67
Let’s test 0++ hypothesis.
In the limit where X(3872), , & J/
rest frames coincide:
ql
dN/dcosql  sin2ql
c2/dof = 34/9
Rule out 0++!
|cosql|
How about 1++?
dN/dcosqdcosc
 sin2ql sin2c
ql
K
c
c2/dof = 11/9
|cosql|
c2/dof = 5/9
Compute angles in
X(3872) rest frame.
1++ looks OK!
|cosc|
Look B→ K D0D00 candidates
D*0→ D00?
M(D0D00)
Signal yield 11.3±3.6 events(5)
|DE|
|DE|
Rule out 2++ !
(Strong threshold suppression.)
Properties of X(3872); what is it?
JPC=1++.
That means cc1’ if it is usual charmonium, but
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Mass is 100MeV off from the prediction.
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Small (J/ g) /(J/ ) disfavors this hypothesis.
→ not likely to be cc1’!
DD* bound state?
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JPC=1++ is favored.
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Isospin violation is predicted
 (J/ g) < (J/ ) is also predicted.
→ looks no contradiction!
Y(3940); what is it?
No obvious charmonium assignment.
Is it ccg hybrid?
• Predicted by QCD,
• Decays to DD and DD* are suppressed
(“open-charm” thresh = mD + m D** = 4.3 GeV)
• large hadron+J/ widths are predicted
• masses expected to be 4.3 ~ 4.4 GeV
(higher than what we see)
→ Need more study
Summary and prospect
X(3872)
•JPC=1++ established.
•Properties are consistent with expectations of DD* bound state.
Y(3940)
•No obvious charmonium assignment.
•Might be ccg hybrid.
•Need more study to have conclusive picture.
The studies shown today are based on 275M BB, while 447M BB have
been accumulated by 2005 summer.
→ following would appear soon,
•More precise measurements of their properties
•Attempts to hunt something new
Back up slides
Example: 1-Use BK ’
J/
z
’
’ is 1-
dN/dcosq  sin2qKm
’: c2/dof = 8.9/9
qK m
K
compute angles in
J/ restframe
D.V. Bugg hep-ph/0410168v2
|cosqKm|
K
|cosqKl| for X(3872) events
c2/dof = 45/9
fit with
1--MC + bkgd
see
8 evts/bin
expect
1&3evts/bin
background
scaled from
sidebands
X(3872) is not 1-- !
M  pJ/· (eJ/ x e)
-+
0
0-+ :
sin2q
c2/dof=18/9
sin2
q
|cosq|
c2/dof=34/9

safe to rule out 0-+
|cos|
M(gJ/) look-back plot
M() can distinguish
-J/ S- & P-waves
S-wave:
c2/dof
= 43/39
(CL= 28%)
P-wave: c2/dof = 71/39
(CL=0.1%)
q*
roll-off
Shape of M() distribution near
the kinematic limit favors S-wave
q*3
roll-off