production of mesons on protons near threshold by linearly polarized photon at spring-8/leps
DESCRIPTION
PaNic02. XVI Particles and Nuclei International Conference September 30 - October 4, 2002, Osaka, Japan. Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS. Wen-Chen Chang for LEPS collaboration - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/1.jpg)
Production of Mesons on Protons near Threshold by Linearly Polarized Photon
at SPring-8/LEPS
Wen-Chen Chang for LEPS collaboration
Institute of Physics, Academia Sinica Taipei 11529, Taiwan
XVI Particles and Nuclei International ConferenceSeptember 30 - October 4, 2002, Osaka, JapanPaNic02
![Page 2: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/2.jpg)
Outline
• Photo-production of mesons at high energy and near production threshold.– Pomeron exchange.– Pseduo-scaler particle exchange.
• How linearly polarized photon beam can help us in distinguishing different sources of contribution?– Spin density matrix element.– Decay asymmetry in Helicity Frame.
• Measurement by LEPS experiment at SPring-8.– Reconstruction of mesons in KK modes.– Angular distribution of K+ in Helicity Frame at forward direction.
• Summary.
![Page 3: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/3.jpg)
Total Cross Section of Hadronic Interaction
XsYsT
Universal Scaling : = 0.5, = 0.08
A. Donnachie and P.V. Landshoff
![Page 4: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/4.jpg)
Photo-Production of Mesons
at Forward Region (small |t|)
Pomeron Exchange Pseudo-scaler Exchange
(OZI Suppressed!)
Exotic knock-out process
![Page 5: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/5.jpg)
Photo-Production of Mesons
at Backward region (large |t|)
Emission from Nucleon Exotic shake-off process
![Page 6: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/6.jpg)
At Forward region:
• Pomeron: – Positive power-law scaling of
s.
– Dominating at large energy.
– Natural parity (=+1).
– Exchange particles unknown; likely to be glueball : P1(J=2+), P2(J=0+, negative power-law scaling of s). (Ref. T. Nakano and H.Toki, 1998)
– Successful phenomenology for diffractive process.
• Pseudo-scaler particle: – Negative power-law scaling of
s.
– Showing up at small energy.
– Un-natural parity (= –1).
– Exchange particles like ,.
– OZI suppressed.
![Page 7: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/7.jpg)
Differential Cross section of p p
with un-polarized photon beams
A.I.Titov et. al., PRC 59, R2993
(t=0
)
![Page 8: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/8.jpg)
With Linearly-Polarized Photon Beam
• Experimentally we measure W’s functions and density matrix
could be determined by spherical harmonics decomposition.
• The contributions of natural and un-natural parity exchange in the t-channel are represented by the matrix element of Re(0), Re(1).
),(cos2sin),(cos2cos
),(cos),,(cos21
0
HHHH
HHHHL
WPWP
WW
H: polar angle of K+ in Helicity frame H : azimuthal angle of K+ in Helicity frame: angle between the photon polarization vector and CMS production plane.
![Page 9: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/9.jpg)
Spin Density Matrix Elements
011
000
2211
210
2111
110
2100
2111
2011
010
2000
000
21
)]2sinsinImsin2sinIm2(
2sin
)2cossincos2sin2cossin(
2cos
2cossincos2sinRe2
cos)13(2
1)1(
2
1[
4
3
),,(cos
HHHH
HHHHHH
HHHH
H
HHL
P
P
W
K.Schilling et. al., Nucl. Phys. B15 (1970) 397
![Page 10: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/10.jpg)
The Spin Density Matrix Elements at small |t| regions
•Two important spin-conserving processes:•Pomeron exchange: 1
1-1= –Im 21-1 = +0.5, and all diagona
l ’s = 0 at =0., exchange: 1
1-1= –Im 21-1 = – 0.5, and all diagonal ’
s = 0 at =0.
A.I.Titov et. al., PRC60, 035205
.1when ,5.0 ;0when ,5.0
2
21
2
||||
1
111
111
2221
11
2
UN
UN
TT
TTT
![Page 11: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/11.jpg)
Angular Distribution of K+ in Helicity Frame
=0, 11-1=+0.5 =1, 1
1-1= – 0.5
)))(2cos(21(4
3),( 1
11
HH PW
![Page 12: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/12.jpg)
SLAC MeasurementJ.Ballam, et. al, PRD 7(1973), 3150
![Page 13: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/13.jpg)
LEPS CollaborationRCNP, Osaka University, JapanH. Fujimura, M. Fujiwara, T. Hotta, H. Kohri, T. Matsumura, N. Matsuoka,T. Mibe, M. Morita, T.Nakano, T. YoritaOsaka University, JapanN. Nomachi, A. Sakaguchi, Y. Sugaya, M. SumihamaAcademia Sinica, TaiwanW.C. Chang, D.S. Oshuev, C.W. Wang, S.C. WangChiba University, JapanH. Kawai, T. Ooba, Y. ShiinoIHEP, RussiaP. ShaginJAERI, JapanY. Asano, N. Muramatsu, R.G.T. ZegersJASRI, JapanS. Date, N. Kumagai, Y. Ohashi,H. Ookuma
Konan University, JapanH. AkimuneKyoto University, JapanK. Imai, T. Ishikawa, M.Miyabe, M.Niiyamma ,M. YosoiNagoya University, JapanS. Fukui, T. Iwata, Y. Miyachi, A. WakaiOhio University, U.S.K. HicksPusan National University, S. KoreaJ.K. AhnSaskatchewan University, CanadaC. RangacharyuluTohoku University, JapanH. ShimizuWakayam Med. University, JapanS. Makino
![Page 14: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/14.jpg)
LEPS detectors
1m
TOF wall
MWDC 2
MWDC 3
MWDC 1
Dipole Magnet (0.7 T)
Liquid Hydrogen Target50mm-long (2000 Dec.-2001June)150mm-long (2002May-July)
Start counter
Silicon VertexDetector
AerogelCerenkov(n=1.03)
![Page 15: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/15.jpg)
Charged particle identification
Mass(GeV)
Mo
men
tum
(G
eV
)
K/ separation (positive charge)
K++
Mass/Charge (GeV)
Eve
nts
Reconstructed mass
d
p
K+
K-
+-
![Page 16: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/16.jpg)
Signal of K+K
![Page 17: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/17.jpg)
Reconstructed events
Large acceptance at forward angles ~5000 ’s (Dec,2000 - June, 2001) Runs with 150mm-long LH2 target (May-July, 2002 ).
KK event Kp event
![Page 18: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/18.jpg)
Experimental Acceptance at -0.2< t < |t|min GeV2
2.2 < E < 2.4 GeV
![Page 19: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/19.jpg)
Simulation at -0.2< t < |t|min GeV2 2.2 < E < 2.4 GeV
=0 =0.5 =1
2222 :)1(|:||| UNN TT
![Page 20: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/20.jpg)
Decay angular distribution of K+ in rest frame (Helicity frame)
|M(KK)-M |< 10 MeV , |M((KK)X)-Mproton|< 30 MeV
-0.2< t < |t|min GeV2 , 2.2 < E < 2.4 GeV
w/o Acceptance Correction
Raw Data
Vertically polarized beamHorizontally polarized beam
![Page 21: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/21.jpg)
Summary
• About 5000 events of photo-production of mesons by linearly polarized photons from E= 1.6GeV(threshold) to 2.4GeV are measured by LEPS experiment at SPring-8/Japan.
• In comparison with measurement at high energy, our preliminary results show that the contribution of natural-parity exchange still composes a larger fraction in the total scattering amplitude while that of un-natural parity component becomes more significant at E=2.3 GeV and t>-0.2 region.
• With the ongoing studies of the acceptance correction and systematic errors, the cross section, differential cross section and spin density matrix elements at the forward regions will be reported in the near future.
A presentation of detailed results will be shown in the poster session:“Polarization observables in the \phi(1020) meson photoproduction withlinearly polarized photons” by T. Mibe (RCNP, Osaka Univ.).
![Page 22: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/22.jpg)
Decay Angular Distribution in p p
![Page 23: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/23.jpg)
Example
![Page 24: Production of Mesons on Protons near Threshold by Linearly Polarized Photon at SPring-8/LEPS](https://reader035.vdocument.in/reader035/viewer/2022081514/56813a5b550346895da251ac/html5/thumbnails/24.jpg)
Super Photon Ring 8 GeV (SPring-8)