Interference between φ and Λ(1520)
production channels in γp → K + K − p
reaction near Threshold
Sun Young Ryu (RCNP, Osaka University)
for the LEPS Collaboration
Outline
1
Photoproduction of φ and Λ(1520) near threshold.
2
Interference effect between φ and Λ(1520) production
channels.
3
Relative phase measurement.
Published in Phys. Rev. Lett. 116, 232001 (2016)
Sun Young Ryu — φ-Λ(1520) Interference — Page 2 of 23
φ Meson Photoproduction
The φ-meson production has the unique feature within gluon
dynamics of being a result of OZI suppression due to the dominant
ss structure .
Sun Young Ryu — φ-Λ(1520) Interference — Page 3 of 23
Bumps in φ Meson Photoproduction
√
The s = 2.1 GeV bump in φ photoproduction has not yet
been explained in detail 1 .
X Excitation of missing
nucleon resonances 2
X Hidden-strangeness
pentaquark state 3
X Rescattering processes 4
X Interference effect
between φ and Λ(1520)
production channels
1
T. Mibe et al. (LEPS), PRL 95, 182001 (2005); H. Seraydaryan et al. (CLAS) PRC 89, 182001 (2005); B. Dey et al.
(CLAS) PRC 89, 055206 (2014)
2
A. Kiswandhi et al., PLB 691, 214 (2010)
3
R. Aaji et al. (LHCb), PRL 115, 072001 (2015)
4
S. Ozaki et al., PRC 80, 035201 (2009); H-Y. Ryu et al., PTEP 2014, 023D03 (2014)
Sun Young Ryu — φ-Λ(1520) Interference — Page 4 of 23
Bumps in φ and Λ(1520) Photoproduction
Similar bump in Λ(1520) photoproduction 5 .
5
H. Kohri et al. (LEPS), PRL 108, 092001 (2012)
Sun Young Ryu — φ-Λ(1520) Interference — Page 5 of 23
Differential Cross Sections for γ p → K + K − p
d2 σ
dmK + K − dmK − p
∝ |Mφ + MΛ(1520) + Mnr |2
≈ |Mφ + MΛ(1520) |2 + |Mnr |2 ,
where Mφ and MΛ(1520) are the complex amplitudes for φ
and Λ(1520) production processes, respectively. Mnr represents non-resonant K + K − p production.
Sun Young Ryu — φ-Λ(1520) Interference — Page 6 of 23
Interference between φ(1020) and Λ(1520)
Differential cross sections for the γp → K + K − p reaction via
the φ and Λ(1520) resonances:
d2 σ
dmK + K − dmK − p φ,Λ(1520)
2
a e iψa
b e iψb
∝ 2
+
,
mφ − mK2 + K − + imφ Γφ mΛ2 ∗ − mK2 − p + imΛ∗ ΓΛ∗ {z
} |
|
{z
}
Mφ
MΛ(1520)
where a = a(Eγ ) and b = b(Eγ ) denote the magnitudes of
the Breit-Wigner amplitudes for φ and Λ(1520).
Sun Young Ryu — φ-Λ(1520) Interference — Page 7 of 23
2
M(K p) (GeV/c )
Interference between Mφ and MΛ(1520)
-
1.65
Eγ=2.023 GeV
1.6
1.55
Λ(1520)
1.5
1.45
φ(1020)
1
1.05
1.1
1.15
1.2
+ -
The integrated cross sections
over the K − p mass interval in the
φ-Λ(1520) interference region
where the two resonances
overlap 6 :
B(mK + K − ) = B(mK + K − , Eγ )
1.252
M(K K ) (GeV/c )
Theoretical calculation 7
2
dσ
ae iψa
iψb + K − )e
∝ 2
+
B(m
K
mφ − m 2 + − + imφ Γφ
dmK + K −
K K
6
Y. Azimov, J. Phys. G 37, 023001(2010)
S. i. Nam et al. (to be published) for the theoretical calculation approach
7
Sun Young Ryu — φ-Λ(1520) Interference — Page 8 of 23
Interference between Mφ and MΛ(1520)
Relative Amplitude
where ψ = |ψa − ψb | is the relative phase between a and B,
m = mK + K − .
|a|2
+ |B(m)|2 +
(mφ2 − m 2 )2 + mφ2 Γφ2
30
20
ψ=0
ψ=
π
2(mφ2 − m 2 )|aB| cos ψ + 2Γφ mφ |aB| sin ψ
10
ψ=+
π/2
0
ψ=-π
(mφ2 − m 2 )2 + mφ2 Γφ2
/2
-10
-20
-30
1.005
1.01
1.015
1.02
1.025
1.03
- +
1.035
2
Maximum constructive at ψ = +π/2
M(K K ) GeV/c
Maximum destructive at ψ = −π/2.
Sun Young Ryu — φ-Λ(1520) Interference — Page 9 of 23
Interference Analysis
Event selection with kinematic fits for γp → K + K − p.
Sun Young Ryu — φ-Λ(1520) Interference — Page 10 of 23
Interference Analysis
Event selection with kinematic fits for γp → K + K − p.
Determinations of |Mφ |2 : a and |MΛ(1520) |2 : B(mK + K − ) by
excluding the possible interference region* with the
0.1 GeV energy interval.
Sun Young Ryu — φ-Λ(1520) Interference — Page 10 of 23
Interference Analysis
Event selection with kinematic fits for γp → K + K − p.
Determinations of |Mφ |2 : a and |MΛ(1520) |2 : B(mK + K − ) by
excluding the possible interference region* with the
0.1 GeV energy interval.
* |MK + K − − mφ | < 4 Γφ ,
Γφ = 4.266 MeV
Sun Young Ryu — φ-Λ(1520) Interference — Page 10 of 23
Interference Analysis
Event selection with kinematic fits for γp → K + K − p.
Determinations of |Mφ |2 : a and |MΛ(1520) |2 : B(mK + K − ) by
excluding the possible interference region* with the
0.1 GeV energy interval.
* |MK + K − − mφ | < 4 Γφ ,
Γφ = 4.266 MeV
* | MK − p − mΛ∗ | < 2 ΓΛ∗ ,
ΓΛ∗ = 15.6 MeV
Sun Young Ryu — φ-Λ(1520) Interference — Page 10 of 23
Interference Analysis
Event selection with kinematic fits for γp → K + K − p.
Determinations of |Mφ |2 : a and |MΛ(1520) |2 : B(mK + K − ) by
excluding the possible interference region* with the
0.1 GeV energy interval.
* |MK + K − − mφ | < 4 Γφ ,
Γφ = 4.266 MeV
* | MK − p − mΛ∗ | < 2 ΓΛ∗ ,
ΓΛ∗ = 15.6 MeV
Relative phase measurement between φ and Λ(1520)
amplitudes in terms of energy in the interference region*.
Sun Young Ryu — φ-Λ(1520) Interference — Page 10 of 23
Interference Analysis
Event selection with kinematic fits for γp → K + K − p.
Determinations of |Mφ |2 : a and |MΛ(1520) |2 : B(mK + K − ) by
excluding the possible interference region* with the
0.1 GeV energy interval.
* |MK + K − − mφ | < 4 Γφ ,
Γφ = 4.266 MeV
* | MK − p − mΛ∗ | < 2 ΓΛ∗ ,
ΓΛ∗ = 15.6 MeV
Relative phase measurement between φ and Λ(1520)
amplitudes in terms of energy in the interference region*.
Measurement of Cross sections for φ and Λ(1520)
photoproduction by excluding the possible interference
region*.
Sun Young Ryu — φ-Λ(1520) Interference — Page 10 of 23
Experiment at LEPS/SPring-8
Compton-Backscattered photon beam and a forward
LEPS spectrometer at BL33LEP beam line, SPring-8.
γp → K − K + p reactions at forward angles from the φ
production threshold (1.573 GeV) to 2.4 GeV.
Sun Young Ryu — φ-Λ(1520) Interference — Page 11 of 23
Number of Events
Particle Identification
10 5
p
+
-
π
π
+
K
10 4
-
K
10 3
All
d
K + K − Detection
10 2
P < 1 GeV/c
10
1
-1
-0.5
0
0.5
1
1.5
2
2.5
Mass/Charge(GeV/c2/e)
K − (K + )p Detection
A typical mass resolution is 30 MeV for 1 GeV kaons.
Sun Young Ryu — φ-Λ(1520) Interference — Page 12 of 23
K + K − p Events from Kinematic Fit P(χ2 ) > 0.02
1.7
2
2
1.8
M(K p) (GeV/c )
K + p detection
M(K p) (GeV/c )
K − p detection
M(K-p) (GeV/c2)
K + K − detection
1.8
1.7
1.7
1.5
1.6
-
1.6
-
1.6
1.5
1.4
1.5
1.4
1
+ 1.2
-
1.42
1.4
1
+ 1.2
-
1.42
2
1.7
-
1.5
1.4
1.4
1
+ 1.2
-
1.42
M(K K ) (GeV/c )
1.8
1.6
1.5
1.5
1.4
1.7
1.6
1.6
1.2
M(K+K-) (GeV/c2)
M(K p) (GeV/c )
M(K-p) (GeV/c2)
1.8
1.7
1
M(K K ) (GeV/c )
M(K-p) (GeV/c2)
M(K K ) (GeV/c )
1.8
1.8
1.4
1
+ 1.2
-
1.42
M(K K ) (GeV/c )
1
1.2
1.4
M(K+K-) (GeV/c2)
Sun Young Ryu — φ-Λ(1520) Interference — Page 13 of 23
MC Simulation for γp → K + K − p in all Eγ Ranges
MC Λ∗
1.6
1.5
1.4
ENTRIES
2571640
1.8
1.7
1.6
1.5
1.4
1
1
2
3
4
1.2
1.4
M(K+K-) (GeV/c2)
ENTRIES
3016340
1.8
1.7
1.6
1.5
M(K-p) (GeV/c2)
11044049
1.7
MC K ∗ (896)
MC Swave
M(K-p) (GeV/c2)
ENTRIES
1.8
M(K-p) (GeV/c2)
-
2
M(K p) (GeV/c )
MC φ
1.4
1
1.2
1.4
M(K+K-) (GeV/c2)
ENTRIES
166817
1.2
1.4
1.8
1.7
1.6
1.5
1.4
1
1.2
1.4
M(K+K-) (GeV/c2)
1
M(K+K-) (GeV/c2)
γp → φp → K − K + p based on Eγ -dependent SDME 2 .
γp → Λ(1520)K + → K − pK + based on the decay angular
distributions from LEPS results 3 .
γp → K + K − p (non-resonant S-wave production)
γp → K(896)0 Σ+ → K + π− pπ0 based on SDME results 4 .
2
W.C. Chang et al. (LEPS) PRC 82, 015205 (2010)
J. Chen, Ph.D thesis (2009)
S.H. Hwang et al. (LEPS), PRL 108, 092001 (2012)
3
4
Sun Young Ryu — φ-Λ(1520) Interference — Page 14 of 23
ENTRIES
-
2
M(K p) (GeV/c )
2-D Fits except the Interference Region
1.8
942
1.7
Real Data
1.6
1.973<Eγ<2.073 GeV
1.5
1.4
1
1.2
+ -
|Mφ |2 and |MΛ(1520) |2 in
the interference region
are estimated from the
magnitudes of MC
templates for φ and
Λ(1520) mass bands.
1.4
2
M(K K ) (GeV/c )
Sun Young Ryu — φ-Λ(1520) Interference — Page 15 of 23
2
P(χ ;30) = 0.895
–
–
10 2
φ
Λ(1520)
10 2
Number of events
Number of events
2-D Fit with MC Templates for γp → K − K + (p)
10
10
2
P(χ ;38) = 0.545
–
–
φ
Λ(1520)
1
1
0.95
1
1.05
1.1 1.15 1.2
+ 2
M(K K )(GeV/c )
1.45 1.5 1.55 1.6 1.65 1.7 1.75
2
M(K p)(GeV/c )
: The invariant mass spectra for K + K − (left) and K − p(right) system
: MC data for non-resonant K + K − p production
Sun Young Ryu — φ-Λ(1520) Interference — Page 16 of 23
Utilizing the MC
linshapes in
Interference Region
-
2
M(K p) (GeV/c )
Interference Region K + K − (p)
1.8
1.7
1.6
1.5
1.4
1
1.2
1.4
M(K+K-) (GeV/c2)
Sun Young Ryu — φ-Λ(1520) Interference — Page 17 of 23
Interference Yields (K + K − )
1.973<Eγ<2.073
60
150
100
40
50
20
0
1
-
1.02
+
1.04
2
M(K K )(GeV/c )
+ : |Mφ + MΛ(1520) |2 + |Mnr |2 ,
0
Interference Yields!
1
-
1.02
+
1.04
2
M(K K )(GeV/c )
– : |Mφ |2 + |MΛ(1520) |2 + |Mnr |2
Sun Young Ryu — φ-Λ(1520) Interference — Page 18 of 23
Number of events
Fit results for the relative phase (K + K − )
50
χ2/ndf = 10.67 / 5
1.773 <Eγ<1.873 GeV
1.873 <Eγ<1.973 GeV
0
-25
-50
Number of events
χ2/ndf = 3.87 / 5
25
ψ
± 13o
−86o ± 9o
98o ± 7o
141o ± 10o
69o
50
25
0
2
-25
-50
2
χ /ndf = 3.62 / 5
χ /ndf = 9.75 / 5
1.973 <Eγ<2.073 GeV
2.073 <Eγ<2.173 GeV
1.01
1.02
1.03
+
P(χ2 , 5; ψ)
56.8%
5.8%
60.5%
8.3%
-
1.01
2
M(K K ) GeV/c
1.02
1.03
+
-
2
M(K K ) GeV/c
Dashed lines are from theoretical estimates with ψ = π/2 (S. i. Nam
et al.)
Sun Young Ryu — φ-Λ(1520) Interference — Page 19 of 23
Integrated Yields and Phases (K + K − )
+π
Phase Ψ
Number of events
500
400
+π/2
300
0
200
−π/2
100
−π
1.6 1.7 1.8 1.9
2
2.1 2.2 2.3
0
1.6 1.7 1.8 1.9
K + K − mode
K − p mode
2
2.1 2.2 2.3
Eγ (GeV)
Eγ (GeV)
K + p mode
Sun Young Ryu — φ-Λ(1520) Interference — Page 20 of 23
Forward Differential Cross section for γp → φp
2
dσ/dt at tmin(µb/GeV )
We reconfirm the bump structure at
1
√
s = 2.1 GeV.
● LEPS(2015)
❏ LEPS(2005)
0.5
0
1.6
1.8
2
2.2
Eγ(GeV)
Sun Young Ryu — φ-Λ(1520) Interference — Page 21 of 23
Differential Cross Sections for γp → K + Λ(1520)
*
dσ/dcosΘ K+(µb)
We also reconfirm the bump structure for γp → K + Λ(1520) at
forward angles.
● LEPS(2015)
1 ❏ LEPS(2010)
0.5
*
0.9 < cosΘ K+< 1.0
0
1.8
2
2.2
2.4
Eγ(GeV)
Sun Young Ryu — φ-Λ(1520) Interference — Page 22 of 23
Summary
The φ-Λ(1520) interference measurement is a good probe to
study the origin of enhanced production cross sections for φ
√
and Λ(1520) near s=2.1GeV.
Sun Young Ryu — φ-Λ(1520) Interference — Page 23 of 23
Summary
The φ-Λ(1520) interference measurement is a good probe to
study the origin of enhanced production cross sections for φ
√
and Λ(1520) near s=2.1GeV.
The relative phases suggest strong constructive interference for
K + K − pairs observed at forward angles.
Sun Young Ryu — φ-Λ(1520) Interference — Page 23 of 23
Summary
The φ-Λ(1520) interference measurement is a good probe to
study the origin of enhanced production cross sections for φ
√
and Λ(1520) near s=2.1GeV.
The relative phases suggest strong constructive interference for
K + K − pairs observed at forward angles.
We reconfirmed the bump structure and found that φ-Λ(1520)
interference effect is not large enough to account for the
bump structure.
Sun Young Ryu — φ-Λ(1520) Interference — Page 23 of 23
Summary
The φ-Λ(1520) interference measurement is a good probe to
study the origin of enhanced production cross sections for φ
√
and Λ(1520) near s=2.1GeV.
The relative phases suggest strong constructive interference for
K + K − pairs observed at forward angles.
We reconfirmed the bump structure and found that φ-Λ(1520)
interference effect is not large enough to account for the
bump structure.
The nature of the bump structure could originate from
interesting exotic structures such as a hidden-strangeness
pentaquark state, a new Pomeron exchange or rescattering
processes via other hyperon states.
Sun Young Ryu — φ-Λ(1520) Interference — Page 23 of 23