Transcript New Results on (3770) and D Mesons Production and Decays From BES Gang RONG (for BES Collaboration) Presented by Yi-Fang Wang Charm07 Cornell University, August 4-8

New Results on (3770) and D Mesons
Production and Decays From BES
Gang
RONG
(for BES Collaboration)
Presented by Yi-Fang Wang
Charm07
Cornell University,
August 4-8
2007
1
Outline
 Introduction
 Inclusive decays of D Mesons
 Measurements of R
 Parameters of (3770)
 B[(3770)non-DD] and Search for
Charmless decays of (3770)
 Summary
2
Introduction
BESII (3770)
data sample of
-1
 about 17.3 pb data taken at 3.773 GeV
about 33 pb-1
 about 7 pb-1 data taken from 3.768 GeV to 3.778 GeV
 about 8 pb-1 data taken from 3.665 to 3.878 GeV
Data Samples
• about 6.5 pb-1 data taken at 3.650 GeV
• about 1 pb-1 data taken at 3.665 GeV
300
250
200
150
pb-1
World (3770) Samples (pb-1)
100
50
0
MARK-I
DELCO
MARK-II MARK-III
BES-II
CLEO-c
3
(by summer,2005)
D- and D0 tags
Double tag analysis
Absolute
measurements
4
D+X
Dtag
K+
De+
P+
D
D+
π–
π–
Singly tagged
D sample
D0    X
With the singly tagged D
sample, we can do some
absolute measurements of D
decays on the side recoiling
against the tags .
D    X
e-
PT
0.52-0.62 GeV
0.62-0.72 GeV
X=any particles
0.72-0.82 GeV
0.82-0.92 GeV
P+
is any charged
particle (, e, π and K)
0.92-1.02 GeV
Nμobs
mKnπ(Dtag)
5
D+X


e
k

N obs
 N true
    N true
 e  N true
 k  N true
 
e

e
k

N obs
 N true
 e  N true
 ee  N true
 ke  N true
 e
μtrue
k

e
k

N obs
 N true
 k  N true
 ek  N true
 kk  N true
 k
etrue


e
k

N obs
 N true
    N true
 e  N true
 k  N true
 

 N true
  

 
e
 N true
   e


k
N
 true    k
    
 N true  
 e
 ee
 ek
 e
i
Nobs =observed particle I;
 k
 ke

 k
  

 e 
 k 

   
kk
Ntruei =
1
πtrue
Ktrue

 N obs



e
 N obs



k
N
 obs 
  
 N obs 
εim= ratio of a particle “i” to
be identified as “m”
true particle i
B( D 0    X )(%)
B( D     X )(%)
ARGUS
6.0±0.7±1.2
-
First measurements
CHORUS
6.5±1.2±0.3
-
BES-II
6.8±1.5±0.6
17.6±0.7±1.3
B( D     X )
 2.59  0.70  0.15
0

B( D   X )
PDG
6.5±0.7
16.1±0.4
D
D

0
 2.54  0.02
PDG
6
De+X and DKX
B(De+X) and B(DKX)
B( D 0  e  X )(%)
B( D   e  X )(%)
CLEO-c
6.46±0.17±0.1
3
16.13±0.20±0.
33
MarkIII
7.5±1.1±0.4
17.0±1.9±0.7
BES-II
6.3±0.7±0.4
15.2±1.0±0.7
PDG2007
6.55±0.17
16.1±0.4
Preliminary
( D   e  X )
 0.95  0.12  0.06
0

( D  e X )
Comparison of Results
B( D   K  X )(%)
B( D   K  X )(%)
B( D 0  K  X )(%)
B( D 0  K  X )(%)
BES-II
24.7±1.3±1.2
15.2±1.0±0.7
57.8±1.6±3.4
3.5±0.7±0.3
PDG2007
27.5±2.4
5.5±1.6
53±4
3.4+0.6-0.4
7
The quantity R
Why are we interested in R(s) ?
• Vacuum polarization correction needs the R(s) values, which
plays an important role in the precision test of the Standard
Model.
• For evaluation of the electromagnetic coupling at the Z mass
scale, QED ( M Z )
• For determination of a  ( g  2) / 2 of the muon.
had, LO
a
 2 ( 0) 
K ( s)

 ds s R( s )
3 2 4 m

2
• Evaluate
 S (s)
• Non-DD decays of (3770)
• important in open charm region for the understanding of 1-resonance production, for searching for new states, and for
studying dynamics …
8
The quantity R
(3770) production & decays
3
3
It is believed to be a mixture of 1 D1 and 2 S1 states of cc
system. It is thought to decay almost entirely to pure DDbar.
Before BES-II & CLEO-c, previously published data indicate that
more than about 35% of (3770) does not decay to DD-bar ?
This conflicts with theoretical prediction.
9
The quantity R
New Measurements
Recently BES and CLEO-c measured the DD and (3770)
production at 3.773 GeV based on the data taken below DD
threshold and at 3.773 GeV.
To uncover the puzzle, a better
way is to make cross section
scan
A better way to measure the cross sections, the widths of the
resonance and the DD branching fractions of (3770) is to
analyze the line-shapes of (3770), (3686) and DD production
simultaneously.
BES made several fine cross section scans covering both the
(3686) and (3770) to measure the resonance parameters,
branching fractions and search for non-DD decays …
10
The quantity R
The Previously Measured quantity R
Including all hadrons
Precision measurement of the
cross sections in this region
11
The quantity R
Definition of different R
Ruds ( c ) ( 3770 ) ( s) 
Ruds ( c ) ( s)  R ( 3770 ) ( s)
above cc-bar threshold
Ruds
below cc-bar threshold
hadrons
[where q is the light (u,d,s) quarks]
Ruds
Evaluate
 S (s)
Rhad(s)=Ruds(c)(s)+ΣRres,i(s),
Rres,i(s) is R values due to all 1－－
resonances decay to hadrons except Ψ(3770).
hadrons
Rhad
calculate
QED ( M Z )
a  ( g  2) / 2
12
The quantity R
ISR corrections

expect
had
( s)  
xmax
0
dx F ( x, s )  B ( s(1  x )) | 1  ( s(1  x )) | 2
s'
 B (s) is Born order cross sections x  1  s
F ( x, s ) is sampling function
Kuraev
& Fadin
F ( x, s )  x  1 V  S  
Effective
c.m. energy
Moninal c.m.
energy
H
the electron equivalent
radiator thickness

2 
s

 
ln
 1
2


 
me


3
   2 1   2  1
s
V S
2 37 

 1  


ln
 2 
2



4
  3 2  24  3 me
4 
 H   1H   2H
x


2

1 2
1 1  3(1  x )2
  4( 2  x ) l n 
l n (1  x )  6 
8
x
x

 1H     1 

H
2

x

13
The quantity R
Vacuum polarization correction
1
 1  ( s )   2 ( s )  ...
1  ( s )
  h  l
h 
s
[ PV 
 (s )
B
'
Vacuum polarization change
the photon propagator
ds'  i B ( s )]
 ig
q
2


 ig
q 2 1   (q 2 )

4 
ss
results in
1 l l 
 l  1   vac
B
2

B
2


 
4
m
2

l l
l
 vac ( s ) 
f ( x),
(x 
)
| 1  ( s ) |2

s
5 x
1  x (2  x )  1  1  x 
f ( x)    
log
 , ( x  1)
9 3
6
1  1  x 
5 x
x  1( 2  x )
1
1
f ( x)    
tan
, ( x  1)
9 3
3
x 1
2
'
expect
 had
(1   ) 
B
Radiative correction factor
14
The quantity R
Results
PRL 97, 262001 (2006)
Ruds ( c ) ( 3770 ) ( s) 
Ruds ( c ) ( s)  R ( 3770 ) ( s)
above cc-bar threshold
Ruds
below cc-bar threshold
Ruds = 2.141±0.025±0.085
Below DD-bar threshold
RpQCDuds = 2.15±0.03
Sources
ΔSYS (%)
Luminosity
1.8
Hadron selection
2.5
M.C. modeling
2.0
ISR
1.5
Ψ(3770) resonance parameters
2.7
Total
(off Ψ(3770) region)
3.9
Total
(within Ψ(3770) region)
15
4.9
The quantity R
Comparison of R measurements from
different experiments
PLB 641 (2006) 145
16
Resonance Parameters of (3770)
New measurements
68 energy points
Dec. 2003 data
( (3770)  DD)  11 MeV(Heikkila
...)
( (3770)  DD)  20.1 MeV(Eichten...)
17
The paper is being in press (PLB)
Resonance Parameters of (3770)
New measurements
Comparison with those measured by other experiments
prd[e+e-(3770)][nb] obs[e+e-(3770)][nb]
Experiment
This work [Dec. 2003 data]
10.00.30.5
7.20.20.4
BES [PRL 97(2006)121801]
9.60.70.4
6.90.50.3
MARKII
9.31.4
M(3770)(MeV)
tot(3770)(MeV)
ee(3770)(eV)
Note
3772.40.40.3
28.51.20.2
2771113
PLB in press
3772.20.70.3
26.92.40.3
2512611
PRL 97(2006)121801
Experiment
PLB in press
B[(3770)e+e-][10-5] 0.970.030.05
[Dec. 2003 data]
PRL 97(2006)121801
PDG
0.930.060.03
1.050.14
[Dec. 2003 data]
Ruds=2.121 0.023 0.084
18
Resonance Parameters of (3770)
What about World Average
Comparison of measurements of
the cross section for (3770)
production
Leptonic branching fraction
PRL 97 (2006)
121801
Preliminary !
obs( 3770 )
[n b]
B[( (3770)  e  e  )]
B[ (3686)  e  e  ]  (0.704 0.122 0.033)%
 105
PRL 97 (2006) 121801
B[ (3686)  e  e  ]  (0.755 0.031)% PDG04
19
B[(3770)non-DD]
PLB641 (2006) 145
BF ( (3770)  D0 D 0 )  (50.1  1.3  3.9)%
BF ( (3770)  D D )  (35.9  1.1  3.5)%
BF ( (3770)  DD )  (86.0  1.7  6.0)%
BF ( (3770)  non  DD )  (14.0  1.7  6.0)%
Determined from
analysis of R values
and DD-bar cross
sections
PRL 97 (2006) 121801
BF ( (3770)  D0 D 0 )  (46.8  5.2  3.2)%
BF ( (3770)  D D )  (37.0  4.1  3.5)%
BF ( (3770)  DD )  (83.8  6.8  6.4)%
BF ( (3770)  non  DD )  (16.2  6.8  6.4)%
BF ( (3770)  D D)  (85  5)%
BF ( (3770)  non  DD)  (15  5)%
Obtained by fitting to
the inclusive hadron
and the DD-bar
production cross
sections
simultaneously.
PDG07
20
Search for Charmless Decays of (3770)
Mode
3.773[pb]
3.650[pb]
Bup[10-3]
0
<3.5
<8.9
<0.5

<12.6
<18.0
1.9
2(+-)
173.78.418.4
177.713.318.8
4.8
K+K-+-
131.710.114.1
161.717.917.1
4.8
+-
<11.1
<22.9
1.6
2(K+K)
19.93.62.1
24.16.52.6
1.7
K+K
15.85.11.8
17.49.22.0
2.4
ppbar+-
33.23.43.8
42.16.14.8
1.6
ppbarK+K
7.12.00.8
6.13.10.7
1.1
ppbar
<5.8
<9.1
0.9
3(+-)
236.714.733.4
234.923.833.1
9.1
2(+-)
153.740.118.4
86.640.310.4
24.3
2(+-)0
80.913.910.0
124.321.714.9
6.2
K+K-+-0
171.626.020.9
222.837.727.2
11.1
2(K+K)0
18.17.72.1
<23.0
4.6
ppbar0
10.12.21.0
9.23.41.0
1.2
ppbar+-0
53.19.26.8
29.011.13.7
7.3
3(+-)0
105.834.416.9
126.647.119.2
13.7
Search for
Charmless
decays of
(3770)
We have searched for
more than 40 modes
for the light hadron
decays.
PLB650(2007)111
21
Search for Charmless Decays of (3770)
Preliminary Results
Mode
K+K-2(+-)
3.773[pb]
3.650[pb]
168.018.223. 164.930.323.
7
2
Bup[10-3]
<10.3
2(K+K-)+-
11.95.81.7
<49.1
<3.2
ppbar2(+-)
23.55.03.5
22.88.43.4
<2.6
4(+-)
131.819.523.6
76.224.413.9
<16.7
K+K-2(+-)0
231.563.637.5
<375.2
<52.0
4(+-)0
<206.9
<119.4
<30.6
0+-
111.913.113.1
113.621.313.1
<6.9
0K+K-
34.211.54.4
57.617.96.3
<5.0
0ppbar
13.13.21.8
17.76.22.8
<1.7
K*0K-+
94.715.510.4 85.526.314.4
Search for lighthadron decays
of (3770)
<9.7
bar
<2.5
<6.1
<0.4
bar+-
<26.7
<42.9
<4.4
22
Search for Charmless Decays of (3770)
Search for light-hadron decays of (3770)
Mode
3.773[pb]
3.650[pb]
Bup[10-3]
+-
<37.1
<50.8
5.5
K+K-
<44.4
<53.2
6.6
ppbar
<20.3
<30.9
3.0
+-0
<25.5
<66.7
3.8
K*0K-+0
116.332.720.0
128.159.517.9
16.3
K*+K-+-
173.973.326.1
189.0116.328.2
32.4
K+K-00
<5.6
47.633.410.7
0.8
K+K-+-
94.231.611.7
141.953.319.7
14.6
bar0
<7.9
<21.4
1.2
Preliminary Results
Upper limits are set at 90% CL
We searched for (3770)light hadrons over 40 channels, but no significant
signals were found. This does not mean that (3770) does not decay into light
hadrons. To extract the branching fractions for (3770)light hadrons from the
observed cross sections, one need to make finer cross section scan covering
23
both (3686) and (3770) with larger data samples (BES-III can do this well).
SUMMARY
• Inclusive decays of D mesons
Measured BF(D+ mu+ X)=(17.6+-2.7+-1.3)% for the first time
Measured BF(D+ K- X)=(24.7+-1.3+-1.2)%
Measured BF(D+ K+ X)=(6.1+-0.9+-0.4)%
Measured BF(D0 K- X)=(57.8+-1.6+-3.4)%
Improved
measurements
• R value
Improved measurements of R in the range from 3.65 to 3.88 GeV
Measured Ruds = 2.121+-0.023+-0.085
Measured Ruds(c)+(3770) for the first time
• (3770) parameters
Precisely measured M(3770) =3772.3+-0.5 MeV; Γtot=28.5+-1.2 MeV;
Γee=277+-16 eV
Precisely measured BF(e+e-)=(0.97+-0.08+-0.05)x10-5
σobs(3770) = 7.15+-0.25+-0.25 nb [combined two measurements]
24
SUMMARY
Combined 49 energy point cross
section scan results and 3 energy
point cross section results (inclusive
hadron and DD-bar cross sections)
• BF[(3770)non-DDbar]
Measured BF[(3770)non-DDbar] = (15+-5)%
Measured BF[(3770)DDbar] = (85+-5)%
PDG07 [BES]
• Light hadron decays of (3770)
No significant signals for (3770)light hadron were found in about
40 channels.
• How to solve this problem ?
Finer cross section scan over (3686) and (3770) to measure the
cross sections for exclusive modes and fitting the cross sections to
extract out the branching fractions (My comment only !)
25
Thank You！
26
Backup slides
27
Comparison with those measured by CLEO-c
BES-II
CLEO-c
BF ( (3770)  non  DD )  (16.4  7.2  4.2)%
obs( 3770 )  6.94 0.48 0.28 nb
 ( 3770 )non  D D  1.1 0.6nb
0.17
 DobsD  6.39 0.10-0.08
nb
0.41
obs( 3770 )hadrons  6.38 0.08-0.30
nb
0.41
 ( 3770 )non  D D  0.01 0.08-0.30
nb
(hep-ex/0512038); PRL 96 (2006) 092002
Based on analysis of inclusive
hadron and DD-bar cross section
scan data.
PLB 141 (2006) 145
Actually, considering the errors, the two results are not in contradiction.28
Comparison with those measured by CLEO-c
BES-II
 DobsD  6.14 0.12 0.50nb
CLEO-c
0.17
 DobsD  6.39 0.10-0.08
nb
obs( 3770 )  7.09 0.19 0.63 nb
 ( 3770 )non  D D  0.95 0.12  0.42nb
Assuming that there are interference between the two amplitudes of continuum and resonance

 6.76 0.19 0.62 nb
 ( 3770 )non  D D  0.62 0.12  0.42nb
obs
 ( 3770 )
0.41
obs( 3770 )hadrons  6.38 0.08-0.30
nb
0.41
 ( 3770 )non  D D  0.01 0.08-0.30
nb
Based on measured R values.
Method:
Method:
BES measured Ruds near DD-bar threshold
and R at 3.773 GeV with traditional method,
then calculate the Born order cross section for
(3770) production. By comparing the cross
sections for DD-bar and (3770) production,
BES obtained the branching fraction. BES
used an ISR generator to simulate the decay
e+e- hadrons and obtain the efficiency for
e+e-  hadrons.
Use parameter
ee( 2 S )  2.33 keV
CLEO-c directly count the number of
hadronic events observed at 3.773 GeV, and
subtract the backgrounds from J/, (2S)
radiative tails and continuum QED
background. CLEO-c used the efficiency for
the decay (3770) J/ π+ π- to estimate the
efficiency for e+e-  hadrons.
Use parameter
29
ee( 2 S )  2.54 keV
Comparison with those measured by CLEO-c
BES-II
Discussion
Method:
CLEO-c
Method:
CLEO-c did not consider the difference of ISR
if we use  ( 2 S )  2.54 keVto calculate the
ISR & vacuum polarization correction factor, & vacuum polarization corrections for
continuum hadron production at the two
and assuming that there are interference
between the two amplitudes of the continuum energy points (3.671 GeV and 3.773 GeV) when
and the resonance, we would obtain
subtracting  ( 2 S ) background at 3.773 GeV.
ee
B( (3770)  non  DD)  (7.3 1.8  6.4 )%
 ( 3770 )non  D D  0.48 0.11 0.42 nb
0.41
 ( 3770 )non  D D  0.01 0.08-0.30
nb
PRL 97 (2006) 121801
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