Inclusive Hadronic Results from BaBar: ISR and Pentaquark
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Transcript Inclusive Hadronic Results from BaBar: ISR and Pentaquark
ISR Physics at B-factories
Vladimir Druzhinin
BINP, Novosibirsk
Initial State Radiation (ISR) Method
d( s, x )
W ( s, x , ) 0 s(1 x ) ,
dxd(cos )
(
W ( s , x , )
x
)
x
( 2 2 x x 2 ) sin2
(sin 2
4me2
s
2 E
s
,
cos2 )2
detected hadrons
θ < 10º or θ > 170º
21º < θ < 138º
e+e-+-+-
• High luminosity at B-factories
allows to use this method for
measurements of e+e- f cross
sections at energies below s
• Wide energy interval in single
experiment
• Greatly reduced point-topoint uncertainty
2
Initial State Radiation Studies at BABAR
• Rely on tagged photon for identification, loose hadronic
selection
• High fiducial efficiency :
– Wide-angle ISR forces hadronic system into the detector
fiducial region
– Collimated hadronic system due to boost.
– Weak dependence on details of fragmentation
• Harder momentum spectrum due to boost:
– fewer problems with soft particles.
• Kinematic fit:
– excellent mass resolution
– background suppression
• Most dangerous background, e+e- f0, can be estimated
from data and subtracted
3
Initial State Radiation Studies at BABAR
• Objective :
Precise cross section measurements for all significant processes,
e+ e- → f , from threshold to c.m. energy ~ 4.5 GeV
• Purpose :
PC = 1Significantly
improve
understanding
of
the
spectroscopy
of
J
states, and of their resonant substructure
Combine the cross section measurements to obtain improved
precision on the c.m. energy dependence of R in this region
• Reactions for which results have been published :
e+ e- p p
e+ e- + - 0
e+ e- 2+ 2-, K+ K- + -, 2K+ 2Ke+ e- 2+ 2- 20, K+ K- 2+ 2• Work in progress on :
+ - , K K , K K 0 , K K h , + - 0 0 , + - 30 , L L ,
L S , S S , d d ,…..
4
(e+e- hadrons)
Contributions to had
magnitude
errors
Burkhardt,
Pietrzyk 2001
s [GeV/c2]
(e e hadrons)
R( s )
0 (e e )
5
Build R from Sum Over Exclusive Final States
Results published by BABAR
0
K+KK0SK0L
R Units
Analyses in Progress
K+K-/h
K0K
00
DD*
6
2K+4
K+K-
K + K -K + K -
y(2S)
pp
J/y
√s' [GeV]
6
+
ee
pp
(232
-1
fb )
Phys. Rev. D 73, 012005 (2006)
e e pp
The cross section depends on two form factors, electric and magnetic.
2
2
2
m
4
C
2
2
p
( e e pp )
G
GE
2 M
2
3m
m
From the total cross section we
obtain effective form factor
2
2 2m p
2
Fp
GM 2 GE
m
2m 2p
1
m2
Ratio of form factors can be
extracted from analysis of angular
dependence
4m 2p G E 2
2
( 1 cos p ) 2
sin2 p
m GM
d cos *p
d
Advantage of ISR measurement:
weak dependence of detection efficiency on mass and
proton polar angle
Model-independent measurement of cross section.
8
Mass spectrum
J/y
232 fb-1
y(2S)
+-
K+K-
pp0
pp0
uds
pp
data
5.9 ± 2.5
2.5 ± 1.0
229 ± 32
13 ± 3
26 ± 4
3737± 75
4025
9
Angular distributions
•angular distributions associated with
GE and GM are:
d (GM )
~ 1 cos2 p
d cos p
d (GE )
~ sin 2 p
d cos p
1.877<mpp<1.950 GeV
GE dominates near m≈2 GeV/c2
Inconsistent with PS170
measurements
1.950<mpp<2.025 GeV
2.025<mpp<2.100 GeV
2.100<mpp<2.200 GeV
2.200<mpp<2.400 GeV
2.400<mpp<3.000 GeV
GM in Blue
GE in Red
10
Cross section
In reasonable agreement with e+e- previous measurements
Negative steps at M ~ 2.2 and 3 GeV (!?)
11
pp : effective form factor
F
GM
2
2m2p
m pp
2
GE
2
1
2m2p
m pp
2
.
• Reasonable agreement with ppannihilation results
• Steep behaviour at threshold can
be manifestation of subthreshold
pp-bound state
12
+
ee
0
(90
-1
fb )
Phys. Rev. D 70, 072004 (2004)
e+e- 0
Key process for study excited -like state
M ' 1350 20 20 MeV/c2 PDG: 1400-1450 МэВ/c2
' 450 70 70 MeV
PDG : 180-250 МэВ
M '' 1660 10 2 MeV/c2 PDG: 1670 ± 30 МэВ/c2
'' 230 30 20 MeV
PDG: 315 ± 35 МэВ
14
e+e- 0
NJ/y = 92034
SND
BaBar
90 fb-1
DM2
M3[GeV/c2]
B(J/y 0)%
BABAR
PDG 2004
BES 2003
2.18±0.19
1.50±0.20
2.10±0.12
• systematic error - 5%
• and -meson parameters are in
agreement with world averages
• Consistent with SND data for M<1.4 GeV
• Inconsistent with DM2 results
15
e+e- 4h:
KK updated
0
0
K K new (232 fb-1)
K K K K
(90
-1
fb )
Phys. Rev. D 71, 052001 (2005)
e e 22 cross section
PRD 71, 052001 (2005)
90 fb-1
Systematic errors:
• 12% for m4 < 1 GeV,
• 5% for 1 < m4 < 3 GeV,
• 16% for higher masses
Good agreement with direct e e measurements
Most precise result above 1.4 GeV
a1(1260) - dominant, f0(1370) final state is seen.
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e+e- K+K-+-, K+K-00, K+K+K-K232 fb-1
e+e- K+K- K+KSystematic error – 25%
90 fb-1
Systematic error – 7-15%
Intermediate states: K*(890)K dominant, , KK
Structures in K+K- cross section near 1.8, 2.2, 2.4 GeV.
18
6h:
3( )
0
0
2( )
K K 2( )
+
ee
(232
-1
fb )
Phys. Rev. D 73, 052003 (2006)
6π final states
J/ψ
• Large improvements upon existing
measurements.
• Structure around 1.9 GeV, already
seen by DM2 and FOCUS (diffractive
photoproduction)
• Little substructure (~1/event)
00
• Large improvement in precision
• Similar Structure around 1.9 GeV
• substantial substructure
–
–
J/ψ
h, 3, h3 seen
, 0, fo(980), …. present
20
e+e-
Fit to e+e-→6π cross section data
3()
J/ψ
4 2
gm2 ei
3/ 2
Acont
2
s
s m i s
e+e- 2() 00
J/ψ
2
M(GeV/c2)
G(GeV)
phase
BABAR
3()
1.88 ± 0.03
0.13 ± 0.03
21 ± 40
BABAR
2()00
1.86 ± 0.02
0.16 ± 0.02
-3 ± 15
FOCUS
3()
1.91 ± 0.01
0.037 ±
0.013
10 ± 30
FOCUS:
PL B514, 240 (2001)
M = 1910
10 MeV
G = 37
13 MeV
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e+e- K+K-2(+-)
• Clear signals for K*0, J/y and y(2S)
• signal in K+K- spectrum ;
mainly from J/y decay
(K+K-2(+-)) (nb)
J/y
y(2S)
K*0
K*0
Band
J/y
J/y
y(2S)
22
J/y and y(2S) decays
Mode
BaBar BF
PDG 2004
J/y 0
(2.18±0.19)%
(1.50±0.20)%
J/y
(3.61±0.26±0.26)10-3
(4.0±1.0)10-3
J/y K+K-
(6.09±0.50±0.53)10-3
(7.2±2.3)10-3
J/y 2K+2K-
(6.7 ±1.0±1.1)10-4
J/y 33
(4.40±0.29±0.29)10-3
J/y 2+2-20
(1.65±0.10±0.18)10-2
J/y h
J/y K+K-22
J/y 22
J/y pp
Mode
New
(4.0±2.0)10-3
New
(1.47±0.41±0.15)10-3
(1.58±0.16)10-3
(5.09 ±0.42±0.35)10-3
(3.1±1.3)10-3
(1.77 ±0.35±0.12)10-3
(1.60±0.32)10-3
(2.22 ±0.16)10-3
(2.17 ±0.08)10-3
BaBar BF
(5.3±1.6±0.6)10-3
New
y(2S) K+K-22
(2.1 ±1.0±0.2)10-3
New
(3.3 ±0.9)10-4
We actually measure
BF(J/y→f)xee
Branching fractions
are obtained using
ee= (5.40±0.18) keV
[PDG]
PDG 2004
y(2S) 2200
y(2S) pp
BES (2.10±0.12)%
better
worse
(2.36 ±0.24)10-4
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DD mass spectrum
• Mass spectrum fitted with
interfering:
✔ y(30)
✔ y(00)
✔ y(0)
✔ y()
✔ y(20)
• Presence of structure at 3.9 GeV
Preliminary
(Not due to a new charmonium state
but to a threshold effect predicted by
E. Eichten et al.,Phys.Rev. D21
(1980) 203.)
24
e+e-Y(4260) + -J/y
ISR photon need not be detected
Confirmation by CLEO-c: e+ e- scan
y(2S)
Y(4260)
•
•
•
•
125 23 событий
Mass - 42588 МэВ
Width - 8823 МэВ
max 50 пб
PRL 95, 142001 (2005)
232 fb-1
• Not seen in total hadronic
cross section small electron
width, but large ( + -J/y )
• Exotic structure: 4q, hybrid,
mesonic or baryonic molecular
• Search for similar states
containing light quarks ().
25
e+e- f0 (980)
26
e+e- f0 (980)
Phase space:
2/=81/51
Resonance:
2/=38/47
Fitted resonance
parameters:
M=2175±10±15 MeV
=58±16±20 MeV
ss partner of Y(4260)?
f0 have large ss
content
ssss state
27
• Cross section measurements:
– Continuous coverage from threshold to Ecm~4.5 GeV for many
processes.
– Eventually combine exclusive cross section measurements to obtain
precise s dependence of R: ~1% below 1 GeV, ~5% for 1-3 GeV
• Spectroscopy of JPC = 1-- states:
–
–
Parameters of excited -, -, -states
New, possibly exotic states: dip at 1900 MeV in e+e-→6π cross
section, Y(4260), structure in f0 at 2175 MeV
• Large luminosity is needed both for R measurement (~1-2%
accuracy can be reached for 1-5 GeV range) and for
spectroscopy.
28
ISR luminosity for 50 ab-1
50 ab-1
detected hadrons
θ < 10º or θ > 170º
21º < θ < 138º
s, GeV IL,fb-1
0.3-0.6
0.4
0.6-1.0
0.4
1.0-2.0
2.2
2.0-3.0
6.8
3.0-4.2
28
4.2-5.0
40
5.0-8.0
60
VEPP-2000
2 fb-1
BES-III
20 fb-1
Resonances produced and
detected:
J/y - 0.25x109
y (2S) – 0.14x109
(1S) – 0.6x109
(2S) – 0.5x109
(3S) – 0.8x109
29