Transcript Prospects of Probing Rare and Forbidden Processes at BES-III

Prospects of Probing Rare and Forbidden
Processes at BES-III
Haibo Li
Institute of High Energy Physics, Beijing.
International Workshop on Heavy Quarkonium
QWG4 – June 27-30 2006, BNL, USA
2006-6-30
Haibo Li
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BESIII Detector
Two rings, 93 bunches:
• Luminosity
1033 cm-2 s-1 @1.89GeV
6 1032 cm-2 s-1 @1.55GeV
Magnet: 1 T Super conducting
6 1032 cm-2 s-1 @ 2.1GeV
MDC: small cell & He gas
xy=130 m
sp/p = 0.5% @1GeV
dE/dx=6%
TOF:
T = 100 ps Barrel
110 ps Endcap
Muon ID: 9 layer RPC
EMCAL: CsI crystal
E/E = 2.5% @1 GeV
z = 0.6 cm/E
Data Acquisition:
Event rate = 3 kHz
Thruput ~ 50 MB/s
Trigger: Tracks & Showers
Pipelined; Latency = 6.4 s
The detector is hermetic for neutral and charged particle with excellent resolution ,PID,
and large coverage.
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Charm Productions at BEPCII
Average Lum: L = 0.5×Peak Lum.; One year data taking time: T = 107s
Nevent/year = exp L T
Resonance
Mass(GeV)
CMS
Peak Lum.
(1033cm-2s-1)
Physics Cross
Section (nb)
Nevents/yr
J/
3.097
0.6
3400
10  109
t+t-
3.670
1.0
2.4
12  106
(2S)
3.686
1.0
640
3.2  109
D0D0bar
3.770
1.0
3.6
18  106
D+D-
3.770
1.0
2.8
14  106
DsDs
4.030
0.6
0.32
1.0  106
DsDs
4.170
0.6
1.0
2.0  106
Huge J/ and (2S) sample at BESIII;
Largest D/DS sample near the threshold.
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Physics Topics at BESIII
I will not talk the lists below, but they are the main motivation of BESIII!
• Charmonium:
J/, (2S), C(1S) in J/ decay,
C{0,1,2} , C(2S) and hC(1P1) in (2S) decay , (1D) and so on
• Exotics : hybrids, glueballs and other exotics in J/ and (2S) radiative decays;
• Baryons and excited baryons in J/ and (2S) hadronic decays;
• Mesons and mixing of quark and gluon in J/ and (2S) decays;
• Open charm factory : Absolute BR measurements of D and Ds decays,
Rare D decay, D0-D0bar mixing, CP violation,
f D+, fDs , form factors in semi-leptonic D decays,
precise measurement of CKM (Vcd, Vcs)
CP violation and strong phase in D Dalitz Decays,
light spectroscopy in D0 and D+ Dalitz Decays.
• Electromagnetic form factors and QCD cross section;
• New Charmonium states above open charm threshold---R values ...;
• t physics near the threshold.
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Search for Rare Processes at BES-III
No any evidence beyond SM is found in the lab based on the accelerators.
No any indication beyond SM in Quarkonium happened.
But I will present my own personal selection of highlights on very
rare processes in Charm and Charmonium decays, from an experimentalist’s
points of view.
Opportunity to probe rare and unusual processes which
are sensitive to new physics at BES-III?
• Rare and forbidden Charmonium decays :
(1) Weak decays of  ;
(2) Invisible decays of quarkonium;
(3) Lepton Flavor/baryon number violated decays;
(4) CP violation in  decays;
• New Physics probe in Charm meson decays:
(5) Rare decays of Charm meson
(6) D0-D0bar mixing
(7) CP violation in D meson decays
• Lepton flavor Violated tau Decays
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Weak decay of 
c
S
u
c
J/

s
c
D0
c
c
d p0()
d
u
c D0
l+
n
l+
n
c
d
s
DS
c
c
D-
c
l+
l-
g
c
c
One estimated the total weak decay
rate of J/: M.A.Sanchis-Lozano
FTUV:93-10
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u
c
u
D0
c
D0
BR 
Haibo Li
New Physics
in loop!
2 /t D
 (2 - 4) 10 -8
J / 
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New Physics in flavor Changing Decays of J/
c  u quark transition: J/   D/Dbar +Xu :
In the Standard Model, these processes are predicated to be
unobservable. They are sensitive to New Physics:
For example:
In top color model: [C.T. Hill: Phys. Lett. B 345, 483 (1995)]
BR(J/   D/Dbar +Xu)  10-5 – 10-6 (mp = 100 – 200 GeV)
Also the following papers:
A. Datta hep-ph/9903461
A. Datta, P. O'Donnell, S. Pakvasa, X. Zhang, Phys.Rev.D60:014011,1999
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Access to Semileptonic Weak Decay of 
Semileptonic decays: based on heavy quark spin symmetry:
BR ( J /  D l n )  0.26 10 ,
 
S
-8
Z.Phys.C62:271-280,1994
M. Sanchis-Lozano
BR ( J /  DS*l n )  0.42 10-8
One can easily get the Cabibbo-suppressed mode from the following
relation:
BR ( J /  DS ln ) BR ( J /   DS*ln ) Vcs


*
BR ( J /  Dln ) BR ( J /   D ln ) Vcd
2
2
 20
One got the following clean prediction based on HQET:
 (  DS*+ l n)
R = ------------  1.5
(  DS+ l n)
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 (  D*+ l n)
R = ------------  1.5
(  D+ l n)
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Search for Weak decay of J/ at BES-II
Look for
58 million J/ data at BES-II
Accepted by PLB: hep-ex/0604005
J /   DS- e +n e
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J /   D - e +n e
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J /  D 0e + e -
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Access to Weak J/ Decay at BESIII (1)
•
J/   DS (DS*) M (M = p, r, ,,’,K, K*,)
J/   PP
hep-ph/9801202, K. Sharma
J/   PV
Mode
Decay
Br(10-10)
( 40% )
Mode
Decay
Br(10-10)
( 40% )
C = S=+1
(c  s )
  DS+ p D0 K0
8.74
2.80
C = S=+1
(c  s)
  DS+ r D0 K*0
36.30
10.27
C=+1,S=0
(c  d)
 DS+K  D+p  D0
  D0 ’
  D0p0
0.55
0.55
0.016
0.003
0.055
C=+1,S=0
(c  d)
DS+K*  D+r  D0r0
  D0 
  D0
2.12
2.20
0.22
0.18
0.65
 (  DS*+ p- )
R = ------------  3.5
(  DS+ p-)
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<
Sensitive to new physics
if larger BRs measured.
Haibo Li
 (  DS*+ r- )
R = ------------  1.4
(  DS+ r-)
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Access to Weak J/ Decay at BESIII (2)
The rate of weak decay of J/ is at
10-8 level, and the inclusive search
at BESIII may be available:
J/   D*+S X
D*+S  DS+ g (soft g )
D+S p+
K*0K+
KSK+
The sensitivity at BESIII: 10-7 – 10-8
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CPV Processes, Vector Quarkonium Decay to KSKS , KLKL
Within Standard Model, the possible CPV processes
1--  KSKS, KLKL are due to K0K0 oscillation!
KSKL
K0
t1 KLKS
t2
t0
KSKS
K0
KLKL
CPV processes
Time evolution of the K0K0 system produced in vector QQ decay
can tell us the possibilities to find KSKL, KLKS, KSKS and KLKL
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The Decay Widths
of CPV Processes
The Partial widths of the   KSKS, KLKL, KSKL are:
where C is the phase space factor.
The ratio RSS and RLL are defined as:
P (KS , KS ) P (K L , KL )

 RLL
P (KS , K L ) P (KS , KL )
In the ratios, the phase space factor C and the strong matrix element
square
are completely canceled, which insure that the ratios
are completely free from uncertainty caused by strong interaction in
the decay.
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Prediction for CPV Processes
•The ratio of RSS (RLL) of KSKS (KLKL and KSKL production rates has
been constructed in a model-independent way:
Haibo Li and Maozhi Yang
Phys. Rev. Lett. 96 (2006) 192001
• Simultaneous measurements of vector quarkonium decays to both KSKS
and KSKL pairs are suggested at higher luminosity e+e- machines (BEPC-II,
DA NE-II, and Super-B). So many systematic errors can be canceled in the
ratio RSS measurements.
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The Predicted Results for CPV Quarkonium  KSKS Processes
BESII: PRD, 69, 012003 (2004)
BESII: PRL, 92, 052001 (2004)
From PDG 2004
We got the following predicted branching factions for CPV
processes :
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Search for CPV Quarkonium  KSKS Processes at BES-II
BESII 58M J/ , J/  KSKS
BESII: PLB 589 (2004) 7
BESII 14M (2S), (2S)  KSKS
The main backgrounds are due to
J/ gKSKS which will dilute the
CP of KSKS final states.
At BESIII, 1010 J/ sample can
be produced per year !
The sensitivity will be 10-8 – 10-9
level for J/ KSKS
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CPV in J/   Decays at BESIII
The measurement of the electric dipole moment of the particles
is very promising as a place to look for further source of CPV,
X-H. He, J.P.Ma and B. Mckellar PRD 47, R1744 (1993); PRD 49 4548 (1994).
The decay amplitude can be parameterized as:
A( J /  )    u ( p1 )[g  (a + bg 5 ) + ( p1 - p2  )(c + idg 5 )] ( p2 ),
CP term
Define the observables :
N+ - N A  +
,
N +N
N + # events  sign[ p  (q1  q2 )]  +
N - # events  sign[ p  (q1  q2 )]  p is the three momentum of ;
q1 and q2 are the momentum of
proton and antiproton from  and 
decays in their rest frame.
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<A> as large as 10-2
current limit of dipole moment:
d < 1.510-16 e cm
With 10 billion J/y sample
d upper bounds
 1.510-18 e cm
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CPV in J/ g Decays
J.P.Ma. R.G.Ping and B.S.Zou PLB, 580, (2004) 163
Assuming CP is introduced by the electric- and chromo-dipole moment of
charm quark, the CP asymmetry can be predicted. Experimentally, the decay
J/ g is easy to be reconstructed. The CP term in Lagrangian is defined :
And one can get the density matrix of the decay:
If CP not violated, we had:
To test CP, one defined the observable at BES-III :
N+ - N B  +
,
N + NN + # events  sign[ K +  p1 K +  ( p1  p2 )]  +
N - # events  sign[ K +  p1 K +  ( p1  p2 )]  -
With
1010
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J/ at BES-III, we expect:
Haibo Li
K+ is the direction e+ beam
and p1 and p2 are the direction
of the two s, where |p1|>|p2|
to distinguish two phi from
each other.
d c  1.2  10 -14 ecm
~
d c  3.6  10 -14 ecm
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Lepton flavor violating processes in J/ decays
Lepton flavor violating (LFV) processes are strongly suppressed in the
Standard Model by power of (small) neutrino masses. Such decays signal
new physics.
PRD63, 016003, S. Nussinov, R.D. Peccei and X.M. Zhang
J /  t ,t  en en t
J /   et ,t  n n t
BESII upper limit
BR(J/  e) < 1.110-6
BR(J/  et) < 8.310-6
BR(J/  t) < 2.010-6
with 58M J/  sample
BESII
 momentum distribution
PLB561, 49 (2003)
PLB598, 172(2004) J/  e, et, t, the sensitivity can be 10-8 – 10-9
at BES-III with 1010 J/ events per year
J/  e- proton +c.c, J/  - proton +c.c
can also be searched for.
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Invisible Quarkonium Decays
With in SM, the invisible quarkonium decays are predicted by:
hep-ph/9806487, L.N Chang, O.Lebedlev and J. N. Ng
With 2-3% uncertainty!
One get:
Br(Y(1S) nn) = 110-5
Br(J/  nn) = 2.69 10-8
Theoretical clean process
can be used to test model
and probe new physics!
New physics may enhance the production rate of the invisible
Charmonium decays.
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MeV Dark Matter Candidates
P. Jean et al Astron. Asronphys 407(2003) L55
C. Boehm et. al PRL 2004
511keV line
Excess of 511 keV gamma ray line (SPI spectrometer
on INTEGRAL ) could be due to scalar dark matter
annihilation. Many studies had been done:
e+e-  U g, U e+e-, at B factory and phi factory, hep-ph/0510147, N. Borodatchenkova et al
e+e-  U g, U  invisible, at B factory and phi factory, hep-ph/0509024, J.F. Gunion,
Vector quarkonium or scalar quarkonium invisible decays, hep-ph/0506151 Bob McElrath
hep-ph/0510147
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hep-ph/0509024
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Invisible Quarkonium Decays
H(QQ)   : looking for invisible decay in Y(nS) and (ns)
n = 1, 2,3 ; hep-ph/0506151 Bob McElrath

C
J/
A
C
Decay rates were estimated with model
independent way by considering the constraint
from observation of WMAP:


J/
A

hep-ph/0509024, J.F. Gunion, D. Hooper,
B. McElrath: prediction by considering
Light Neutralino Dark Matter :
(nS)  gs A (0 0)
V=J/ or 
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Charmonium Invisible Decays at BES-III
(2S)  p+p- J/
(2S)   J/
(2S)  p0 J/
(2S)  g C
J/ or C nn at BESIII
Two body decay will be easy since the missing
momentum is mono-energitic
(2S)  p+p- J/ ,  J/ and p0 J/ (J/ +- ) can be used as control
sample to understand the event shape and background of J/  nnbar.
Missing momentum of 
pmiss
mgg
Distributions in
(2S)   J/
(J/ +-)
Missing momentum of p0
Distributions in
(2S)  p0 J/
(J/ +-)
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mgg
pmiss
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Sensitivities of Charmonium Invisible Decays at BES-III
3109 (2S) events per year at BES-III
The sensitivity at BESIII will be 10-6 -10-7
for J/, C and C  Invisible.
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Looking for /’ Invisible Decays in J//’
Tag direction
No any hit information are required
outside of the core of  decays.
• Reconstructing K+K- ,
Missing
direction looking at missing momentum of  decays
• Fast  (1.2 GeV) will help us define the decay
direction of invisible decay of / (958) .
Signal MC
58 M J/
 missing momentum distribution
BR (  invisible )
 1.65 10 -3 @ 90%C.L.
BR (  gg )
BR ( '  invisible )
 6.69 10 -2 @ 90%C.L.
BR ( '  gg )
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Preliminary at BES-II.
Being Submitted to PRL.
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Study of invisible decays of , , ’,  and r in J/ two body decays
10X109 J/ events per year at BES-III
The sensitivity at BESIII will be 10-5 -10-6 for , ’ Invisible
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e- (-t) Universality Test in  and DS Decays
e- universality in  decays, current experiments:
BR ( J /  e + e - )
 (1.009  0.024),
+ BR ( J /    )
H+
s
( D  t n )
R

+
( D   n )
+
S
+
S
+
mt2+ (1 m + (1 2
mt2+
m
2
DS+
2
m +
mD2 +
)2
( DS+  t +n )
R
 (12.549  5.5)
+
+
( DS   n )
)2
S
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At BESIII, 1010 J/
sample,
the error will
be 10-4 , namely :
(xx  0.001)
Haibo Li
R relative error: 1% at BES-III
with 20 fb-1 at 4170 MeV
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Probe New Physics in Charm
Decays
D-mixing is the last chance to see
New Physics in meson oscillations!!!
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D-Dbar
mixing


D0 (t )
t  D0 (t ) 




i
 ( M - i  2)
  D0 (t ) 
 D0 (t ) 
SM for |x|
SM to |y| New Physics to |x|
m
x

K ,p , K ,p
D
0
D0
K ,p ,p , K
R mix 
(
1 2
x + y2
2

y
2
)
x, y in range of
10-7-10-2
x  y : signal for New Physics?
x  y : Standard Model?
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A.A. Petrov hep-ph/0311371
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Charm Mixing –Quantum Correlation at BES-III
Quantum Correlations in D0D0 decays from the (3770) allow measurement of strong phases
and mixing parameters from BESIII:
Coherence simplifies study DCSD interfere away so not a background:
Unmixed: D 0  K -p + , D 0  K +p -  ( K -p + K +p - )
mixing: D 0  K -p + , D 0  K -p +  ( K -p + K -p + ) D 0 D 0  ( K  e n )( K  e n )
2
( D 0 D 0  ( K -p + )( K -p + )) x 2 + y 2 p B 2 K -p +

2
0
0
- +
+ 2
( D D  ( K p )( K p ))
2
q B K +p • BESIII PID system
( D 0 D 0  (l l  )) x 2 + y 2

0
0
 
( D D  (l l ))
2
•Two missing neutrinos in events
–dE/dx, resolution (6-7)%
–Two layer barrel TOF, time resolution
~100ps, ~83% solid angle coverage
–1 layer endcap TOF, ~110ps
• Selection efficiency is >20% with a K/π
double mis-identification rate at < 10-4
level
•Electron PID can suppress background
•The selection efficiency is similar as the
Kπ channel
•Background level is also negligible while
running a small MC data sample (~1% of
20fb-1). More detail study is needed.
With 20fb-1(4-5 years running) at Ψ(3770) peak
RM <10-4
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Combined Sensitivity of Charm Mixing @BES-III
Fully using the Quantum
correlation in (3770)DDbar
decays or data above 3770
MeV with final states DD*
to extract mixing rate.
BESIII
The sensitivity of
RM measurement
a few 10-5
at BES-III with
20fb-1 data at
(3770).
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Mixing parameters using Quantum Correlation
From PRD 73 034024 (2006)
by Asner and Sun
Have to identify C=+1 of gD0D0bar and gD0D0barπ0
from D*Dbar and D*D*bar decays
Using single and double
CP/flavor tags –complicated
analyses
parameter
CLEO-c (3x106D0D0)
BESIII(7.2107 D0D0)
C=-1
C=+1
C=-1
C=+1
value
y
0
±0.015
±0.007
±0.003
±0.002
x2
0
±0.0006
±0.0003
±0.00013
±0.0001
cosδKπ
1
±0.15
±0.13
±0.035
±0.04
xsinδKπ
0
─
±0.010
─
±0.003
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CP eigenstate Tags
•CP +
•CP –
–K+K- (3.89X10-3 )
–KSπ0(0.012)
–π+π- (1.38X10-3 )
–Ksη (3.9X10-3)
–Ks π0π0
–KS η’ (0.0094)
–π0π0 (8.4X10-4)
–KSρ0 (0.0078)
–KSKS (7.1X10-4)
–Ksω (0.012)
–ρ0 π0 (3.2x10-3)
–KSφ (4.7X10-3)
In 20fb-1 Ψ(3770) data, we can get
CP+ tags : 4.5x105 ; CP- tags : 3.6x105
With large sample of CP tags, we will definitely improve the measurements
of strong phase, probe the direct CP, and other mixing parameters
2006-6-30
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CP Violation at ψ(3770) at BESIII
K+
Find:
K
-
D
0
D
ACP 
Af
2
Af
2
- Af
2
+ Af
2

2 Im( A1* A2 ) sin( 1 -  2 )
A1 + A2
2
2
+ 2 Re( A1* A2 ) cos(1 -  2 )
•CP violating asymmetries can be measured by searching for
events with two CP odd or two CP even final states:
0
π
π
-
+
p+p-, K+K-, p0 p0, Ksp0 ,
for the decay of ψ  f1 f 2
CP( f1 f 2 )  CP( f1 )  CP( f 2 )  (-1) L  CP(ψ)  +
ACP sensitivity 10-2 - 10-3
K K vs pp
Beam
constraint
Mass
2006-6-30
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Rare and forbidden Charm Decays
Estimation of sensitivity of the rare and forbidden decays of Charm
meson at BES-III with 20 fb-1 at (3770)
Haibo Li, hep-ex/0605004
D+
D0
2006-6-30
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Brief Summary for Charm mixing
 Charm provides great opportunities for New Physics studies
–large available statistics (20 fb-1)
–mixing: x, y = 0 in the SU(3) limit (as V*cbVub is very small)
–mixing is a second order effect in SU(3) breaking
–it is conceivable that y ~ x ~ 1% in the Standard Model
From Alexey Petrov
Charm 2006
–it is possible for y to be dominated by New Physics
 Quantum coherence will allow BES-III to perform new measurements of strong
phases in charm mixing studies
 Quantum coherence will allow BES-III to perform new studies of mixing
–no DCSD contamination in double-tag Kp studies
 Observation of CP-violation or FCNC transitions in the current round of
experiments provide “smoking gun” signals for New Physics
- untagged asymmetries are more sensitive to CPV
2006-6-30
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Lepton Flavor Violation in t Decays
George Lafferty
Charm 2006
2006-6-30
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LFV experimental summary
90 % CL Upper Limits on Br(l -  X -)
U.L.
U.L.
Decay
Decay
George Lafferty
Charm 2006
[BABAR / BELLE]
Decay
U.L.
- e-g
1.2  10-11
- e-e+e-
1.0  10-12
- e-gg
7.2  10-11
t- e-g
1.1  10-7
t- e-e+e-
2.0  10-7
t- e-e+-
1.9  10-7
t- -g
6.8  10-8
t- e-+-
2.0  10-7
t- -e+-
1.3  10-7
t- e-e-+
1.1  10-7
t- -+-
1.9  10-7
t- e-p0
1.9  10-7
t- -p0
4.1  10-7
t- e-’
10  10-7
t- -’
4.7  10-7
t- e-
2.3  10-7
t- -
1.5  10-7
t -  e- K *
3.0  10-7
t- e-KS
5.6  10-8
t- -KS
4.9  10-8
t- -r0
2.0  10-7
t-e-K+K-
1.4 · 10-7
t-e-K+p-
1.6 · 10-7
t-e-p+K- 3.2 · 10-7
t--K+K-
2.5 · 10-7
t--K+p-
3.2 · 10-7
t--p+K- 2.6 · 10-7
t-e-p+p-
1.2 · 10-7
t--p+p-
2.9 · 10-7
t-p-
0.7  10-7
t-e+K-K-
1.5 · 10-7
t-e+K-p-
1.8 · 10-7
t-e+p-p-
2.0 · 10-7
t-+K-K-
4.4 · 10-7
t-+K-p-
2.2 · 10-7
t-+p-p- 0.7 · 10-7
2006-6-30
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LFV experimental summary
Alex Bondar
Prospects at BES-III
Charm 2006
BES-III limit with 12 million tau pairs above the threshold ! Same sensitivity as current
B factory 500 fb-1 data.
BES-III
range
It is not a good place to study LFV in tau decay at BES-III
New Physics
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Summary
With 1010 J/ and 3.2 109 (2S) samples at BES-III, we can look for
many rare and forbidden decays of Charm and charmonium,
and challenge the SM.
• Rare and forbidden Charmonium decay :
(1) Weak decays of  ;
(2) Invisible decays of quarkonia;
(3) Lepton Flavor/baryon number violated decays;
(4) CP violation in  decays;
• New Physics probe in Charm meson decays:
(5) Rare decays of Charm meson
(6) D0-D0bar mixing
(7) CP violation in D meson decays
We expect to locate the search of tiny contributions from
new physics at heavy flavor sector after anything new can
be found at LHC!
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