j-parc e15 実験の今後の展望
DESCRIPTION
J-PARC E15 実験の今後の展望. 平岩聡彦 京都大学 On behalf of the J-PARC E15 collaboration. Outline. Introduction experiment & theory of K - pp J-PARC E15 experiment method setup background Possibility of E15 exp. @ 30kW Summary & outlook. Introduction. Low-energy KN interaction. - PowerPoint PPT PresentationTRANSCRIPT
OutlineOutlineIntroduction
◦experiment & theory of K-ppJ-PARC E15 experiment
◦method◦setup◦background
Possibility of E15 exp. @ 30kWSummary & outlook
2010/12/2-4 ストレンジネス研究会 2010 2
Low-energy KN interactionLow-energy KN interactionK-nucleon interaction
◦Low energy Kp scattering ◦Kaonic hydrogen level shift (KEK-PS
E228)
Kaonic nuclei◦Kaon bound states with a few nucleons◦Extract the information about KN
interaction below KN threshold
2010/12/2-4 ストレンジネス研究会 2010 4
M.Iwasaki et al. , PRL 78, 3067(1997)Attractive (I=0)
How strong?
•DISTO
▫ pp K+X+, X+ p▫ B = 105±2(stat)±5(syst) MeV
= 118±8(stat)±10(syst )MeV
Experimental results on KExperimental results on K--ppppFINUDA
◦ Invariant mass of back-to-back p pairs in K- absorptions
◦ B = 115±6(stat)±4(syst) MeV = 67±14(stat)±3(syst) MeV
2010/12/2-4 ストレンジネス研究会 2010 5M.Agnello et al. , PRL 94, 212303 (2005)
T.Yamazaki et al. , PRL 104, 132502 (2010)
Theoretical study on KTheoretical study on K--pppp
KK--pp bound states should exist!pp bound states should exist!◦ A deep state or shallow state?◦ Decay width is sufficiently narrow?
2010/12/2-4 ストレンジネス研究会 2010 6
B.E [MeV] [MeV] Method
Yamazaki and Akaishi 48 61
(mesonic)Variational Method (ATMS)
Shevchenko, Gal, and Mares
55-70 90-110
(mesonic)Coupled ChannelFaddeev Calculation
Ikeda and Sato 60-95 45-80
(mesonic)Coupled ChannelFaddeev Calculation
Nishikawa and Kondo ~126 Skyrme Model
Dote, Hyodo, and Weise
20±3 (s-wave)
40-70 (mesonic)
Chiral SU(3)Variational Method
Arai, Oka, and Yasui depend on gΛ*Λ*σVariational Method(as Λ*p state)
Formation spectra : in-flight Formation spectra : in-flight 33He(KHe(K--,n),n)
2010/12/2-4 ストレンジネス研究会 2010 7T.Koike and T.Harada. , PLB652 (2007) 262
quasi-freebound
K- escape
K- conversion
KK-- + + 33He He “K “K--pp” + n @ Ppp” + n @ PKK=1GeV/c, =1GeV/c, =0º=0º
YA potential Signal can be
clearly seen!
Integrated production cross section amounts to 3.5 mb/sr.
Search for KSearch for K--pp bound states at pp bound states at J-PARCJ-PARC
2010/12/2-4 ストレンジネス研究会 2010 8
E15 experiment via in-flight (K-, n) reaction on 3He. E27 experiment via d(+, K+) reaction.
J-PARC E15 experimentJ-PARC E15 experiment Experimental search for KExperimental search for K--pp bound pp bound
states usingstates usingin-flight (Kin-flight (K--, n) reaction on , n) reaction on 33HeHe
2010/12/2-4 ストレンジネス研究会 2010 10
K-3He Formation K-pp
clusterneutron
p
p
-
Mode to decay charged particlesDecay
Missing
mass
Spectroscop
y
via neutron
Invariant
mass
reconstructio
n
We can observe both the“Formation” and “Decay” of K-pp bound state
1 GeV/c
Experimental SetupExperimental Setup
2010/12/2-4 ストレンジネス研究会 2010 11
J-PARC K1.8BRNeutron counter
Beam sweep magnet
Cylindrical Detector System
Beamline Spectrometer
1.0 GeV/c K-
NeutronTOF length 15mMissing mass resolusion for
K-pp (B.E. 100
MeV ) ~ 9.2 MeV/c2 (Pn~1.3GeV/c,
TOF=150ps)
Invariant mass resolution
for K-pp (B.E. 100 MeV)
~ 13 MeV/c2 (CDC=200m,
B=0.7T)
Identification of Identification of pn final state pn final state by CDS & NCby CDS & NC
2010/12/2-4 ストレンジネス研究会 2010 12
Possible background- 0pn final state + missing- QF- + missing- QF-, conv. + missing
Other processes can be clearly separated!!
Background?? : two nucleon Background?? : two nucleon absorptionabsorption
2010/12/2-4 ストレンジネス研究会 2010 13
2NA + N rescattering / conversion looks like a “signal” ??
(2NA itself is not a problem.)
2NA is very small
12C(K-,n) @ 1GeV/c
12C(K-,p)
T. Kishimoto et al., Prog.Theor.Phys. 118(2007)181.
De Broglie wave length @ 1 GeV/c ~ 1.2 fmNN distance in 3He ~ 2.25 fm
Proc. Jpn. Academy,Series B83 (2007) 144.
These probabilities are expected to be very small ...Anyway, let’s see how they look like!
Signal(DISTO) vs Background(2NA+Signal(DISTO) vs Background(2NA+ conv.)conv.)
2010/12/2-4 ストレンジネス研究会 2010 14
2NA and - conversion
(B.E.=100MeV =100MeV)
Signal(DISTO) vs Signal(DISTO) vs Background(2NA+rescattering)Background(2NA+rescattering)
2010/12/2-4 ストレンジネス研究会 2010 15
2NA and s-wave scattering
2NA and s-wave scattering
Possibility of the E15 Possibility of the E15 experiment with 30kW PS experiment with 30kW PS
operationoperation
2010/12/2-4 ストレンジネス研究会 2010 16
Yield estimation (1week run Yield estimation (1week run @30kW)@30kW)
Yield = NKaon x t x (d/d)=0º x R x r x A x e x ◦ Nkaon : kaons per spill (@30kW) 300k /spill
◦ t : target 0.08 [g/cm3] / 3 [g/mol] x 6.02x1023 [mol-1] x 9.3 [cm] ~ 1.4 x 1023 [cm-2]
◦ (d/d)=0º : differential cross section @ =0º 3 [mb/sr]
◦ R : Kpp decay branch (p) 0.5◦ r : branching ratio ( -p) 0.63◦ A : acceptance (NC + CDS) 5.3 [msr]◦ e : NC efficiency 0.3◦ : overall efficiency (trigger, detector, ana etc...) 0.7
2010/12/2-4 ストレンジネス研究会 2010 17
4.5 x103 signals can be collected in 1 week run with 30kW operation.
PLB 652 (2007) 262.PRC80 (2009) 055208
Missing mass of Missing mass of 33He(KHe(K--, n), n)
2010/12/2-4 ストレンジネス研究会 2010 18
pp // 00pp decay branches stand on same decay branches stand on same mass!mass!
4,500 signals (p) + 4,500 signals (0p) ~ Total 9,000 signals ( [p] : [0p] = 0.5 :
0.5 )
Improvement of statisticsImprovement of statistics
2010/12/2-4 ストレンジネス研究会 2010 19
Statistical improvement can be achieved by “one proton missing”. Missing proton resolution: 28 0.3 MeV/c2 ()Acceptance (NC+CDS)
◦ 3body phase space 0.079% (all detected) 0.12% (one proton missing)
◦ K-pp (B=100MeV, =100MeV) 0.042%(all detected) 0.098% (one proton missing)
pn final state still can be identified!
x2
SummarySummary & outlook & outlookJ-PARC E15 experiment
◦search for a K-pp bound state using in-flight (K- n) reaction on 3He
◦measure the missing mass in (K-, n) reaction and the invariant mass via the decay of K-pp, simultaneously.
E15 experiment @ 30kW operation◦Enough statistics for the first physics data
can be collected within a week if the cross section is ~ 3 mb/sr. (2% of the requested beam time)
We wish to start E15 exp. as soon as possible . (after E17)
2010/12/2-4 ストレンジネス研究会 2010 20