hypothetical new scaler particle x for q + and its search by the (k + , x + ) reaction
DESCRIPTION
Hypothetical new scaler particle X for Q + and its search by the (K + , X + ) reaction. T. Kishimoto Osaka University. Contents. Current status of + search Another explanation of + Could + be made from K N? X as a K bound state Experiment to search for X (KEK-PS E548). - PowerPoint PPT PresentationTRANSCRIPT
May/27/05Exotic Hadron WS
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Hypothetical new scaler particle X for + and its search by th
e (K+, X+) reaction
T. KishimotoOsaka University
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Contents
• Current status of + search
• Another explanation of +
• Could + be made from K N?
• X as a K bound state
• Experiment to search for X (KEK-PS E548)
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First evidence of from SPring8n K KK n
1.540.01 GeV< 25 MeVGaussian significance 4.6Target: neutron in Carbon nucleus
Background level is estimated by a fit in a mass region above 1.59 GeV.
Assumption:• Background is from non-resonant K+K- production off the neutron/nucleus• … is nearly identical to non-resonant K+K- production off the proton
+
Phys.Rev.Lett. 91 (2003) 012002
hep-ex/0301020
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Positive results
(Table: courtesy of A. Airapetian) Mass~1540 MeVWidth <10 MeV
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+ width from the KN database
A. Sibirtsev et al., hep-ph/0405099 PK(GeV)
•The background is smooth (~4 mb).
•The + with a narrow width should appear as a bump.
•If not, a strong limit on the width can be put.
=20 MeV
=1 MeV
< 1 MeV
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Negative results
(Table: courtesy of A. Airapetian)
Consistent explanation?
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+: Another explanation• Consistent theoretical (quark) model
– yet to be worked out• KN bound state arXiv:hep-ex/0312003 (T.K and T.Sato and others)
• Mass ~1540 MeV– M(KN) ~1570 MeV (30 MeV bound)– 10 MeV/particle (usual)
• Spin parity ½+ (original prediction) – K N system (s-wave) ½+
• This conjecture explains all + properties particularly – Narrow width– Seen in Low Q, unseen in High Q
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Could + be a KN bound state
• Known two Body interaction– N: weakly attractive– KN: weakly repulsive– K weakly attractive
• K int. may have ambiguity– So strong to make K bound state
X (new scaler particle)
No bound state
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• In order to decay– KN ! KN ( has to be absorbed in N) N (s-wave) ! N (p-wave)– K-N (s-wave) ! K-N (p-wave)
• KN have to interact simultaneously
• Width ~ (strong) (R(int)/R())6
– R(int): Radius of Interaction– R(): Radius of
Width of + in KN conjecture
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How to Decay
K NK
N p
p
K Np
Decay
(R(int)/R())6
s s
R()R(int)
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Radius of + (and X)
Asymptotic wave function ()
EB=30 MeV 15 MeV r~ 2 fm r~ 3 fm Extended object
Seen only in Low momentum transfer reaction
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• Width ~ (strong) (R(int)/R())6
(strong) ~ a few 100 MeV– R(int) ~ 1 fm Radius of Interaction– R() ~ 3 fm Radius of
• () ~ 300 x (1/3)6 ~ 0.3 MeV– Consistent with observation
• Production of + → low q2 reaction
Width of + in KN conjecture
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• K interaction may be strong enough to make a bound state: New particle X
• 0- + 0- → 0+ scaler particle
• Binding energy less than 30 MeV– If deeper than 30 MeV + decays into N and X– Probably a few MeV bound – Very extended object
New hypothetical particle X: K bound state
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X (Why missed)
• Lowest order decay mode X ! K– No strong decay MX< MK + M
– No X→K decay • (0+ → 0- + 1- L non cons. )
– No X→K e+e-
• (vec. curr. vs axial charge (0+→ 0-)
• No such decay mode is listed in PDG• No experimental searches ever made (Probably)
• If it exists.– Hard to believe but possibility is there.
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Experiment to search for X
• extended object→Low q2 reaction – r(X)~4fm: q2~ 50 MeV/c
• Lowest q2 reaction • p(K-+ , X-+)p
• @PK~1 GeV/c – q ~ 50 MeV/c
• X ! K
0
50
100
150
200
0.6 0.8 1 1.2 1.4 1.6 1.8 2
p(K,X)p BE=0p$(K^+,X)$ BE=25 MeV
Inci dent momentumPK (GeV/ c)
Mome
ntum
tran
sfer
q(Me
V/c)
MX=mK+mMX=mK+ m- 30 MeV
Momentumtransfer i nthe p(K+, X+) reacti on
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How to measure (KEK-PS-E548)
• p(K-+ , X-+)p, X! K – Measure Kaon momentum in coincidence with rays
• BG process: p(K-+ , K -+ 0), 0 !
• X particle gives highest PK
• Measure invariant mass of K and two ‘s– Dedicated detector system
• Study of K final state interaction
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Cross section
0
2 .5
5
7 .5
1 0
1 2 .5
1 5
1 7 .5
2 0
2 2 .5
2 5
1 0- 1
1 1 0 1 02
K +pto ta l
K +pe la s tic
Cros
sse
ctio
n(m
b)
K+ momentumGeV/
PK~1.05 GeV/cInelastic : ~5 mb( production)
(X) ~ (K) x f f: low relative momentum phase space Reaction mechanism
b/sr order (1/1000)
KEK-PS E548
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K + momentum (PK=1 GeV/c)
K + scattering angle (cos )
K + scattering angle (cos )
K +
mom
entu
m (MeV/
c)K
+ m
omen
tum
(MeV/
c)
K + p → X + p
K + p → K + 0 p
Signal
Background
Max950 MeV/c
Max 830 MeV/c
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Experimental condition (E548)• K+ beam from K2 beam line at KEK-PS
– PK=1.2 GeV/c– 50k for 3x1012ppp
• Target: 20cm thick H2O and 20 cm thick CH2
• Trigger – (K+, K+) x NaI(>5 MeV) – Rate ~ 500 ev/spill
• NaI – Target region: 5x5 top and bottom
• 10.5 cm from the beam center– Forward counter: 3x4 top and bottom
• 13cm from the beam center
• Data taking went well (2 days in this April)
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Spectrometer
E548Study of kaonic nuclei by (K-, p) reaction
Search for X particle by (K+, K+ ) reaction
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Current setup of E548
BAC 2
BAC 1
LC Target(water)
BQC
NaI 5x5
NaI 3x4
CV
VZH
K+Beam 1.2GeV/c
γ
γK+
FAC
KURAMA
BS
10.5cm
20cm
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K+ momentum Tagged by 2γ
X particle production
π0 production
K+
mom
entu
mK
+ m
omen
tum
2 γ backward
PK=1.2 GeV/c
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Typical cross section
• 0 production cross section ~ 5 mb
• ~10-3 of 0
– 1 MeV bound X (r~ 10 fm)
• ~10-2 of 0
– 5 MeV bound X (r~ 4 fm)
33
23
__
10)/1(
)()(
R
rdeinfind
d
d
d iqr
prodprodX
K+ X+
pp
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Expected yield (Extension requested)
• NK ： 50 k/spill
• NT ： 20cm （ water target）
• X + cross section
~10 -3 of 0
•
•
bdd
d 5
1.0
spill
spillk
dd
dNNY anaTK
/101
1.07.010510618
120/50
2
3023
7.0ana Beam Time ‥ 18shift
⇒Xparticle ~1600
<r>~10fm, BE~1MeV
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Summary
• K bound system X is hard to believe
• Might have been missed experimentally
• Explains almost all + properties
• If found, it means we found a new scaler particle (like strange partner of σ)
• It is not only a solution of + but opens new world.
• Wait for our results