A light pseudoscalar in a model (2) O with lepton family symmetry
Search for the missing excited hyperon statesR. Badui C. Yero/D. Puentes J. Bono . Two Pseudoscalar...
Transcript of Search for the missing excited hyperon statesR. Badui C. Yero/D. Puentes J. Bono . Two Pseudoscalar...
Search for the missing excited hyperon states
Lei Guo Florida International University
Overview • Compared with the N* sector, the spectrum of hyperons
receives less attention – For S=-1 sector, only 14 Λ, and 10 Σ states have been
established – For S=-2 sector, only 6 Ξ states have been established – For S=-3 sector, only 2 Ω states have been established
• Most hyperon data came from kaon-beam experiments • Photoproduction is a great alternative for strangeness
production – Photon beam has intrinsic component – CLAS, CLAS12 and GlueX offers great opportunities in all
hyperon sectors
ss
QM predictions for S=-1 Hyeprons (>2.0GeV)
S. Capstick et al., PRD34, 2809 (1986)
What have been established?
State Rating Λ(2100) 7/2- **** Λ(2110) 5/2+ **** Λ(2350) 9/2+ *** Σ(2030) 7/2+ **** Σ(2250) ?? ***
J. Beringer et al, (PDG), PRD86 , 010001, (2012)
Plenty are missing; Can we discover at least one new state?
Various Unseen/Rare Decay Modes of Hyperons
• Y*ΞK – Believed to be the leading contributor to Ξ photoproduction
(Oh, Nakayama et al) – Never been established; – Upper Limit was set for Λ(2100) and Σ(2030)
• Y*Λ/Σ+η Λ(1670)Λη, Σ(1750) Ση
• Radiative Decay of exited hyperons – Only two have been measured
• Σ(1385), and Λ(1520) • Y*Λ/Σ+η’ – Never been seen
LQCD prediction for the S=-1 Hyperon Spectra
H.-W. Lin, “Review of Baryon Spectroscopy in Lattice QCD”, Chin.J.Phys 49, 827(2011)
Number of states compatible with QM predictions More expected from the Jlab LQCD group?
Production Mechanisms of Hyperons
• Λ(1520) photoproduction dominated by K* exchange • Λ(1520) elctroproduction: more K exchange • Exchange particle information can be extracted via angular distribution/PWA • Other exited hyperons? unknown! • Ξ: photoproudced via intermediate hyperons? • Ω: photoprodcution mechniasm Totally unknown
Guo et al., PRC76, 025208 (2007)
Barrow et al., PRC 64, 044601 (2001)
Barber et al., Z. Phys. C7,17(1980) SLAC
CLAS
CLAS
CLAS g12 experiment
g12: Photoproduction on a proton target Integrated luminosity: 68pb-1 Eg: up to 5.5GeV Circular polarization: ~70% Target: Unpolarized Channels for hyperon spectroscopy: ! p! pK
+K
"
! p! K+#!,#! p" "
! p! K+#" 0
! p! K+## /$ /# '
! p! K+K
+$",$
"! " "
#
R. Badui C. Yero/D. Puentes J. Bono
Two Pseudoscalar Meson Photproduction: ππ VS KK (non-resonance region)
π-
π+ p π+
π- p
π-
π+ p
Lack of pK+ resonances reduction of one major diagram Different interference pattern?
Beam Helicity Asymmetry:ππ VS KK
φ: Angle between the two-meson plane/production plane Eg: 2.8-5.5 GeV
Strautch et al., PRL 95, 162003 (2005)
! p! p" +" "
! p! pK+K
"R. Badui, FIU
Key difference: sin2φ vs sinφ
Different strengths (not necessarily fair comparisons)
)>-
K+
),(K-
K+
(K× γ z,×<y +K
φ0 50 100 150 200 250 300 350
I
-0.3
-0.2
-0.1
0
0.1
0.2
0.3 / ndf 2χ 8.581 / 5
p0 0.00165± 0.008239 p1 0.002656± 0.01918 p2 0.002408± 0.03782 p3 0.002257± -0.02716 p4 0.00196± -0.1587
/ ndf 2χ 8.581 / 5p0 0.00165± 0.008239 p1 0.002656± 0.01918 p2 0.002408± 0.03782 p3 0.002257± -0.02716 p4 0.00196± -0.1587
- K
+ p K→ p γ
Beam Helicity Asymmetry: as a function of the two-meson-plane/produciton-plane angle
)-
K+M(K1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9
I
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
° 18± °= 270 )>
- K+),(K
- K+ (K× γ z,×<y
+Kφ ° 18± °= 270
)>-
K+),(K-
K+ (K× γ z,×<y +K
φ
)-
M(p K1.5 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3 2.4
I
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
° 18± °= 270 )>
- K+),(K
- K+ (K× γ z,×<y
+Kφ ° 18± °= 270
)>-
K+),(K-
K+ (K× γ z,×<y +K
φ
• Fit with Fourier series • Sinφ dominates • Strength at fixed angles changes as a function of pK-/KK mass • Need model comparison
Fourier Coefficient as a function of invariant masses
No model/prediction on the market Collaborating with W. Roberts (FSU)
Beam Helicity Asymmetry: as a function of the hyperon plane-produciton plane angle
)>-
),(p K-
(p K× γ z,×<y p
φ0 50 100 150 200 250 300 350
I
-0.3
-0.2
-0.1
0
0.1
0.2
0.3 / ndf 2χ 9.181 / 7
p0 0.002362± -0.02527 p1 0.002487± -0.0254 p2 0.002245± 0.1668
/ ndf 2χ 9.181 / 7p0 0.002362± -0.02527 p1 0.002487± -0.0254 p2 0.002245± 0.1668
- K
+ p K→ p γ
)-
K+M(K1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9
I
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
° 18± ° = 90)>
-),(p K
- (p K× γ z,×<y
pφ ° 18± ° = 90
)>-
),(p K-
(p K× γ z,×<y p
φ
)-
M(p K1.5 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3 2.4
I
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
° 18± ° = 90)>
-),(p K
- (p K× γ z,×<y
pφ ° 18± ° = 90
)>-
),(p K-
(p K× γ z,×<y p
φ
Sinφ term dominates
• The asymmetry strength is mostly flat as a function of w • Strong dependence on pK- invariant mass -- higher mass hyperons? • Need theoretical predictions for comparison
Collaborating with W. Roberts
Fourier Coefficient as a function of invariant masses
JPAC input?
PWA for Y*pK-
PWA software test run Only 3/2 spin allowed Working with JPAC:
Background: X K+K-
PyPWA: C. Salgado Nov 18th talk Can import meson background amplitudes
Waves for different M values: Offer decay/exchange information
Λ(1520) region
Radiative Decay of Excited Hyperons
CLAS Results in PDG
Σ(1385)Λγ
!("! ) /!("" )
Λ(1520)Λγ
!("! ) /!total
The radiative decay is related to the meson Cloud effect on the magnetic moment, and the quark wavefunctions of hyperons Others? None observed
PRC 71, 054609 (2005)
π0 γ
MM(pπ- )>0.55
g12 prospect
Radiative Decay of Excited Hyperons
) 2) (GeV / cΛ γM(1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 2.1
) 2
Cou
nts
/ 8 (M
eV /
c
100
200
300
400
500
600
) 2) (GeV / cΛ γM(1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9
Co
un
ts /
8 M
eV
10
210
310
410
• Preliminary studies: Puentes et al, FIU • π0 contamination needs to be estimated • Kinematic fitting to be used • 25% statistics shown • Data promising
• Multiple background processes ! p! K
+"(! )
Λ polarization in K+Λ/K*+Λ photoproduction
R ! P2+C
x
2+C
z
2
• 100% polarization in K+Λ photoproduc,on • Various models suggest similar behavior in • K*+Λ photoproduc,on
! p! K+"(" 0
)
) 0π +M(K0.5 0.6 0.7 0.8 0.9 1 1.1 1.2
) 2
Co
un
ts /
7 (
Me
V /
c
0
200
400
600
800
1000
1200
1400
CLAS g12 data Yero et al, FIU
Prior CLAS results (Tang et al, PRC 87, 065204 (2013) ) did not publish polarization results
Feasibility ! p! K
+"(" /# /" ')
Y*Λ/Σ+η Two states reported
Y*Λ/Σ+ω Some limits established
Y*Λ/Σ+η’ Never been seen
Beam helicity asymmetry could be studied Statistics limited for (PWA) Future experiments (CLAS12/GlueX) Could also be due to strange meson’s decay to K+η/ω/η’
Ξ- induced olarization in photoproduction
γ K+
π0 p Y*
K+
Ξ- s s d
s s d
First time measurement! (Bono Ph.D Thesis, 2014)
Ξ- Polarization in photoproduction
Theoretical curves from Nakayama et al Model variants: Pseudoscalar/Pseudovector coupling/High-mass hyperons
Man et al., PRC83, 055201, (2011) Nakayama et al., PRC74, 035205 (2006)
• Results VS prediction: Limited by statistics • R~0.3
VS R~1 for Λ results • Unable to distinguish models • Future data expects multiple orders of magnitude more statistics
GlueX CLAS12: Very Strange Experiment
CLAS12 Very Strange Experiment: Expected Particle Rate
Detected particles
Measured Decays
Overall Efficiency
Rate/hr Total Detected
Ω- K+K+K0 ~3.9% ~3.6 ~7k Ω- K+K+K0K- Ω- ~0.5% ~0.5 ~1k Ξ- K+K+π-
Ξ-
~9.3% ~440 ~0.9M
Ξ-(1530) K+K+π- Ξ-(1530) ~7.4% ~140 ~270K
Ξ-(1820) K+K+K-p
Ξ-(1820)Λ ~0.63% ~6 ~12K
• Assuming half field and 80 beam days • Vertex Efficiency/Branching Ratio included
21
Spin-Parity Determination of Ξ* • Spin can be measured by angular distributions (PWA) • Parity measurement challenge: Minami ambiguity Ξ*Y (1/2+) + M1 (0-): two solutions JP • Double Moment Analysis (DMA) Y (1/2+) B (1/2+) + M2 (0-) Double moments: H(lmLM)= Σ DL
Mm(θ1, φ1) Dlm0(θ2, φ2)
DMA: )10(
)1(2
12)1()11( 2
1
LMHLL
JPLMH
J
+
+!=
+
• Linear dependence gives simple, multiple tests for J, P for any odd L≤2J and M≤L
22
CLAS12: Parity Measurement of Ξ(1820)
Ξ(1820) counts: ~50 Need to detect whole decay chain
ImH
(11L
M)
ImH(10LM)
Biagi et al., Z.Phys.C34, 175 (1987)
CERN-SPS Ξ-Be reaction
!
3
2
"
!
3
2
+
Ξ(1820) Needs corroboration
!
3
2
"
CLAS12 estimate: ~12k Ξ(1820) with complete decay chain At CLAS12 (80 beam days) 23
M (!K0)(GeV / c
2)
)2) (GeV/c+K+MM(K1.5 1.6 1.7 1.8 1.9 2 2.1
2Ev
ents/
10Me
V/c
0
20
40
60
80
100
120
140
160
180
200
220
Im(H(103M))-0.015 -0.01 -0.005 0 0.005 0.01 0.015
Im(H(113
M))
-0.015
-0.01
-0.005
0
0.005
0.01
0.015-
25
-
21
-
23
+
21
-Ξ
*θcos
-0.8 -0.6 -0.4 -0.2 0 0.2 0.4
- ΞP
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
=0.1-ΞP=0.3-ΞP
=8.25 GeVγE
CLAS12: Ξ- Polarization and Ξ-(1820) Spin-Parity
• Ξ- polarization measurement: (should be Eγ dependent) • Ξ-(1820) double moments
! p! K+K
+"#! K
+K
+" #($)
! p! K+K
+"#(1820)
"#(1820)! K
#($! " #
p)
Expected M(ΛK-) spectrum
Expected double moments (L=3)
Expected PΞ- vs Eγ
(statistical uncertainty only) 24
Ξ – (1820)
Pythia background
Summary • Hyperon Spectroscopy offers multiple opportunites for
S=-1/-2/-3 sectors • CLAS data already has multiple promises
– First measurement of pK+K- beam helicity asymmetry measurements
– First measurement of Ξ- polarization in photoproduction – Radiative decays of excited hyperons could be extended – K*Λ polarization can be investigated and compare the Λ
polarization mechanism (VS KΛ photoproduction) • CLAS12/GlueX would be gold mines for hyperons
– Y*Λη/ω/η’ – Ξ polarization: Much higher statistics; PWA of Y->KΞ – Excited cascades and Ω- photoproduction