Neutrino-­nucleus­(nucleon)­Reaction­Measurement­by­J-PARC­MLF­sterile­

neutrino­search­experiment­(J-PARC­P56)

Takasumi­Maruyama­(KEK)­for­J-PARC­P56­working­group

Contents• Introduction­of­new­J-PARC­P56­experiment– Setup– Neutrino­flux­and­Neutrino­Interaction

• Possible­feed-backs­to­low­energy­neutrino­interaction

• Comparison­to­other­experiments,­LSND,­KARMEN

­M.­Harada­et­al,­­arXiv:1310.1437­[physics.ins-det](A­brand-new­experiment­proposed­on­2-Sep-2013)­

J-PARC Facility(KEK/JAEA ）

Bird’s eye photo in January of 2008

South to North

Neutrino Beams (to Kamioka)

JFY2009 Beams

30GeV MR

Hadron hall

Materials and Life

Experimental Facility

JFY2008 Beams

3 GeV RCS

CY2007 Beams

181MeV Linac

400MeV (done)

25Hz 300kW now & will be 1MW(beam is back from a few weeks ago; first beam after the accident.)

５４０ nsec

Neutrino­production­and­detector­site­(3F)

3GeV­proton

Detector@3rd floor(50 ton fiducial, 17m baseline)

Neutron Hg target(& neutrino source)

Detector­location­isStill­under­discussion

Using neutrinos from only decay at rest • Neutrinos­from­only­­decays­are­

used.­(­has­long­lifetime).­(top)

• Energy­spectrum­of­­­­e+­­e­decay­is­well­known­(bottom)– Useful­to­examine­the­excess­of­e­­.

– ­­e­oscillation­is­searched.­­

• -­­-­decay­chain­is­highly­suppressed­(10-3­compared­to­+­)

­­

• Proton­energy­of­J-PARC­is­3GeV,­thus­+/p­ratio­is­higher­than­LSND­/­KARMEN­(0.8GeV)­by­5-10­times

Selecting muon decay(~74%)

E.g.;­energy­spectra­(SN­vs­DAR)

arXiv:hep-ph/0307222

• J-PARC­P56­provides­similar­neutrino­energy­range­to­those­of­Super-Nova

Target­ ­­­­absorb capture suppression x

LSND H2O ­­­­­­­­­­­­96% 88% ­­­­5x10-3­­­­­­­­­­­­x­­­­­­­­­0.13J-PARC Hg(+Fe+Be)­­­­­­­99% ~80% ­­­­1.7x10-3­­­­­­­­­x­­­­­1.

~­1.7x10-3­Intrinsic­background.

MLF mercury target and Intrinsic eBKG estimation

3GeVproton

Fe

Mercury target

Be

Be

H

H

For beam pipe

Detector­considerations• Type,­size,­fiducial­mass,­constraints;

– Double-Chooz­type– Diameter­6m,­height­4.4m;­­fiducial­is­25­ton– Two­identical­detectors.­­(from­MLF­constraints)– Movable­detectors.

• 150­10”­PMTs– good­photo-coverage­

­<15%/sqrt(E).

• 50cm­noGd-LS­buffer­region­­veto­and­self-shield­

Detector;­Liquid­scintillator

• Positrons “prompt” signal (E = Evis+0.8MeV)• Neutrons “delayed” signal

Prompt signal

Delayed signal

neutron

proton

positronsAntineutrinos

Gd

gamma

gamma

gamma

electrons

• Coincidence­between­positron­and­neutron­signal­­­­­­­­­­(e­+­p­­e+­+­n;­Inverse­Beta­Decay;­IBD).

• Neutrons­are­captured­by­Gd,­and­emit­gammas­­­­­­­(­totalE­=­8MeV,­lifetime;­a­few­10­s.)­

• Cross­section­of­IBD­is­well­­­known.­­(~2%­uncertainty)­­­­(­=­9.3­x­E

2­x­10-44­cm2)

• Energy­spectrum­of­anti-neutrino­is­also­well­known.­­event­energy­shape­is­also­well­known­for­signal­and­BKG­­

­­c1998

absorbed before decay into ’sthere should not be e at the level of 7x10-4

Signal : e p→e+n np→d MeV)

600s 120Hz­­target+beam­stopconfiguration­­­­DIF,­n­bkg.

Linac­beamAlmost­DC­beam

Cherenkov­photon­can­be­detected.­->­angle­meas.

­­­­­­­­­­­­e­+­e­+­

e

KARMEN

• KARMEN­uses­segmented­Liquid­scintillator­­­­­detector.­(~50ton)­­(left­plot)• Location­is­similar­to­P56,­17m­from­the­ISIS­­­­­­neutron­target.­­(right­plot)­thick­iron­shield­surrounds­the­detector.• ISIS­gives­pulsed­proton­beam,­like­J-PARC.­­But­intensity­of­ISIS­is­weaker­than­J-PARC­

Other­neutrino­interactions• This­experiment­aims­to­search­for­sterile­neutrinos­via­neutrino­oscillations.– Via­IBD;­­e­+­p­­e+­+­­n­

• However,­this­experiment­can­also­provide­good­opportunity­to­measure­neutrino­interactions­precisely­in­the­low­energy­region.– e­+­C­­­­e-­+­Ng.s.­­(Ng.s.­­­C­+­e+­+­e)­­­(*)

– e­+­C­­­­e-­+­N*

– ­+­C­­­+­C*­(11.51­MeV­­emission)­­­(*)– e­+­e-­­e­+­e-­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­(*)

(*)­;­cross­section­is­well­known.

Cross­sections,­#events­

Averaged xs

J-PARC P56 (/4year/50t) LSND KARMEN Cross

section

I.B.D. 7.2x10-41 800 --- ~10arXiv:hep-ex/0203021

Well­known

e­+­C­­­­e-­+­Ng.s. 8.9x10-42 23000 ~3000arXiv:hep-ex/0105068

~1500arXiv:hep-ex/9806024

Well­known

e­+­C­­­­e-­+­N* 4.3x10-42 11000 ~1500arXiv:hep-ex/0105068

---

­+­C­­­+­C*­ 2.8x10-42 O(10000) --- ~500Phys.Lett. B267 (1991) 321-324

Well­known

e­+­e-­­e­+­e-­ ~3.0x10-43­ O(1000) ~1000arXiv:hep-ex/0101039

---­ Well­known

• J-PARC­P56­has­larger­stat.­10­times­than­those­of­previous­experiments.­->­stat­error­1/3

• The­detector­and­beam­of­P56­also­has­better­quality,­therefore­systematic­uncertainties­will­be­improved.

• Ratio­between­charged­current­vs­neutral­current­gives­extra­information.­­ M.­Shaevitz,­2011­Workshop­on­Baryon­&­Lepton­Number­Violation

Energy­and­angle­distributions­of­e-arXiv:hep-ex/0105068

(a);­e­+­e-­­e­+­e-­­scattering­­(left­­Ee,­right;­angle­between­neutrino­and­e-)­(b);­e­+­C­­­­e-­+­Ng.s.­­(Ng.s.­­­C­+­e+­+­e)­(c);­e­+­C­­­­e-­+­N*­­­­(excited­states)

Forward­scattering ­~isotropic

e­+­C­­­­e-­+­Ng.s.­­(Ng.s.­­­C­+­e+­+­e)

• Top-right;­hep-ex/0105068(LSND)

­­­­Cross­section­d/dE• Prompt­signal­has­following­features;– Q-value­is­17.3MeV 　　　

（ E­=­17.3MeV­+­Ee-)– Reconstructed­neutrino­energy­measured­by­LSND­experiment­is­shown­by­bottom-right­plot.

• This­is­also­possible­background­Ee<16.83MeV­

e­+­C­­­­e-­+­Ng.s.­­(Ng.s.­­­C­+­e+­+­e)

• Delayed­signal­from­Ng.s.­­decay­can­be­detected– End­point­of­positron­energy­is­

16.83MeV.– Lifetime­is­15.9­ms– Positron­energy­of­the­b­decay­is­

described­by­following­eq.

δ ；　 Z/e,­­Emax=16.83,­­­­­­­­­­Ee­:­positron­total­energy• Branching­ratio­of­this­­decay­

is­about­94.6%.­• KARMEN­/­LSND,­previous­

experiments­observed­this.­­

­decay­energy­spectrum

KARMENarXiv:hep-ex/0203021

Prompt­e-time­from­beam

Prompt­e-­energy

time­between­e-­and­e+­

e+­energy

Test­for­other­detectors­/­materials­?­• Energy­spectra­of­neutrinos­are­very­clear

– Ideal­test­facility­/­experiment­to­measure­low­energy­neutrino­cross­sections­(O(10MeV))­.

– ­We­can­test­not­only­liquid­scintillator­but­also­other­detectors­/­materials­(E.g.;­Water,­Liquid­Argon,­etc..).­

• Previous­experiments,­LSND,­KARMEN­already­measured­the­cross­sections.­J-PARC­P56­can­improve­precision­of­the­measurements.– Number­of­events­are­increased­by­factor­of­5-10.­(because­of­

higher­proton­energy­(3GeV)­than­others­(800MeV))– Ultra-pure­neutrinos­from­+­can­be­available.­(LSND­

experiment­suffers­from­neutrinos­from­­/­K­due­to­almost­DC­beam)­

– Detector­will­be­improved­­­– Monochromatic­~30MeV­neutrinos­from­­and­~250MeV­

neutrinos­from­K+­is­also­available.­(on­bunch­->­vs­BKG­rate)

On-bunch­beam• Decay-at-Rest­neutrino­source­

provides­­monochromatic­~30MeV­neutrinos­from­­and­~250MeV­neutrinos­from­K+­on-bunch.­(top­plot,­no­time­selection­case)

• This­is­also­a­good­chance­to­measure­the­neutrino­interactions.

• One­difficulty­is­to­manage­backgrounds­from­neutrons­or­neutrinos.­­­­challenging,­but­not­impossible.­­­­­

Theoretical­prediction­(a­few­%­precision)

KARMEN­measurement­­(~15­%­precision)

Monochromatic­MeV­from­­is­used

1ton scintillator

PHITS (MC)

MC­(PHITS)BL13;­­1ton­data

(normalized­by­area)

Neutron which produces BKG.

Neutron BKG @3F isSmaller than 1F by 104

• Top-left;­scintillator­location­­­­­at­MLF­1st­floor• Top-middle;­­­­50×50×450cm3­­scintillator• Top-right;­­­­­­­horizontal­->­timing­­­­­­vertical­;->­­activity­energy• Bottom-middle;­comparison­­­­­­between­data­and­MC.­­­­(for­neutron­background)­­­­->­agreed­well

• Bottom-left;­simulation­prediction­of­neutron­flux.­­Neutron­flux­at­3F­is­smaller­than­that­of­1F­by­order­of­104.­­->­will­be­confirmed­soon.­

BKG measurement at MLF 1F

Summary• J-PARC­MLF­provides­a­good­opportunity­to­measure­the­neutrinos­cross­section­in­meson­Decay-At-Rest­energy­region­(O(10MeV))­in­detail.

• Statistical­error­and­systematic­uncertainty­of­measurements­from­previous­experiments,­LSND,­KARMEN­will­be­improved­by­J-PARC­P56.­

• Cross­sections­for­other­materials­(detector)­can­be­measured­using­the­good­quality­beam.­

• If­you­are­interested­in­the­measurements,­or­implementing­MC,­let­us­know.­