FUTURE EXPERIMENTAL PROGRAM for neutrino cross sections

Sara Bolognesi (CEA Saclay)

A hot topic...

Oscillation measurements in far detector constrained from near detector (xsec x flux) : aim to ~1% uncertainty on signal normalization at future long baseline (T2K 2016 ~5-8 %)

● different Eν distribution ● νµ → ν

e, νµ

● different acceptance and target

neutrino interactions on nuclei (C,O, Ar) → need to model nuclear effects on initial and final states

● Eν inferred from final state leptons/hadrons which have limited angular acceptance,

threshold on low energy particles, very small info on recoiling nucleus...

Measurement of ν xsec at ND is experimentally complicated:

● Eν not known: xsec measurement always convoluted with flux

2/14

→ rely on models to extrapolate :

ND→FD extrapolation :

Many experiments Near detectors for long baseline oscillation experiments:

● T2K (T2K-2, T2HK): ND280 (!) → ND280 upgrade, INGRID (!), WAGASCI

● DUNE ND under discussion: NOMAD-like and/or Liquid Argon TPC and/or HP Ar TPC

Future intermediate detectors for HyperKamiokande ● TITUS (?)● NuPRISM (?)

Dedicated xsec experiments:● Minerva (!)

Accessory measurements: LARIAT, DUET (!) : pion FSI

Annie : neutron capture in Gd

● ArgoNEUT (!)

Short baseline program at FNAL : MicroBooNE, SBND (previous talk)

→ Captain-MINERVA (?)

● Emulsion T60 experiment at T2K flux

(?) = not yet funded

● NOVA ND

● COHERENT, CONNIE: ν Neutral Current interactions through nuclear recoil at MeV scale (SuperNova ν physics)

(!) = running now

3/14

Different approaches

Multipurpose

Argon TPC (liquid or HP)

Water-cherenkov detectors

ND280 (T2K):precise tracking (magnetized)

INGRID (T2K):

Mai

nly

scin

tilla

tors

7m

WAGASCI (T2K):(can be filled of water)

Minerva

MicroBooNE SBND

TITUS

NuPrism

Captain-Minerva

ArgoNEUT (MINOS)

NOVA near detector

4/14

What do we need to measure?

● different neutrino flavor (because of oscillation)

● ν (ν) flux has typically a wrong sign component

measurement of cross-section in the larger possible phase-space: increase angular acceptance of ND

A-scaling: measure cross-sections on different targets (and/or on the same target of FD)

measure all particles in the final state: low threshold for protons, calorimetric approach (neutrons?)

measure cross-section asymmetries between different neutrino species → ν vs ν (magnetization, Gd doping)measure xsec for ν

e (calorimetry)

● different acceptance

● different target

● different Eν distribution

(because of oscillation)

Uncertainties in ND→FD extrapolation :

5/14

A-scaling: water targetSuper(Hyper)-Kamiokande use water as target → need to control nuclear effects on Oxygen

Water as target but passive material

Water doped with scintillator (under discussion for ND280 upgrade)

Water Cherenkov (TITUS, NuPrism)

WAGASCI concept: (to be installed in T2K flux on axis)

Fine Graned Scintillator in ND280

carbon interactions as background to oxygen intreactions→ mainly C/O xsec constrain

H2O CH

threshold: particles have to reach scintillator (compromise: small granularity vs H

2O/C mass ratio)

PiZero detector in ND280water bags can be emptied: water-in vs water-out → absolute Oxygen xsec measurement but larger statistical uncertainty

● limited reconstruction capability: Cherenkov threshold, no pion discrimination, no sign discrimination by itself (need muon spectrometer or Gd doping)

● same target and acceptance as Far Detector

6/14

AcceptanceFar Detectors have typically 4π coverage while Near Detectors optimized for forward going particles → need to enlarge ND acceptance to high angle and backward tracks

● ND280 event display

v

Most of the events are forward tracks

Backward tracks: if only 1 muon track observed, need to distinguish between forward µ+ and backward µ- → TOF between detectors (NEW results soon: 4pi CCincl xsec!)

Still vertical tracks difficult (lot of material and no TPC coverage)

● Possibility for ND280 upgrade:

+ scintillators all around for TOF+ calorimetry (ν

e)

v

TPC TPC

TPC

TPC TPC

TPC

TPC

Scintillator target

Water target

horizontal targets surrounded by TPCs to get 4p acceptance

7/14

Measurement of outgoing protons

Very limited predictivity of proton kinematics from models! And difficult interpretation of the results: disentangling nuclear effects on initial state (Fermi momentum, 2p2h, ...) from Final State re-interactions

NEW Measurements expected from ND280: proton kinematics and transverse variables (proton threshold for good tracking/ID ~500 MeV)

ArgoNEUT: small statistics but powerful Ar technology → MicroBooNE!

Gas Ar would give even smaller threshold: NEW results from ND280 TPC will come (small stat) → HP TPC under discussion

T60: emulsion detector in front of INGRID at T2K flux (high stat: few thousands νµ)

EmulsionINGRID

Main limitation:

'Calorimetric' approach Measurement of all the energy around the vertex or all the energy in the event

νµ Q2<0.2 GeV2

Minerva Collaboration, Phys.Rev.Lett. 111 (2013) 022502,

● Calibration issues (no sensitivity to neutrons, energy threshold...)

- inclusive energy for low momentum particles

- Eν from total deposited energy (and q3 from muon

kinematics) ~ electron scattering data

● Very limited predictivity from models!

The two problems are tightly convoluted and difficult to disentangle

A taste of the future → DUNE:

Example from NOVA:

● need to reconstruct precise Eν shape for good sensitivity (two oscillation maxima)● capability of full reconstruction of tracks and showers down to very low threshold

→ need to reach very good control on detector calibration/uniformity and on neutrino interaction modelling which have convoluted effected in Eν

Main limitation:

9/14

NEW: xsec re-tuning

OLD

Minerva

Future long baseline experiments: νe and ν xsec

We are interested to νe

appeareance and δCP

from ν – ν comparison

In future (HK, DUNE) large samples of 4 ν species → the uncorrelated uncertainties are relevant

● For DUNE assumed: uncorrelated νµ - νµ 5% and ν

e - ν

e 2%

νe-ν

e uncorrelated 1-2%

● HK needed uncertainty to have negligible impact on δ

CP:

HK

DUNE

→ equivalent to factor 2 in exposure!

5% ± 1%

5% ± 2%

5% ± 3%

10/14D

UN

E an d H

K ta lk s @

Nu F

ac t 20 1 5

ν versus ν

(Annie experiment on FNAL beam to test technology)

Very well measured in multipurpose magnetized detectors like ND280

Large water cherenkov detectors: eg, TITUS

● Side magnetised MRDs (1.5T): iron interleaved with air gaps and scintillators

Neutrino flux has always a background component from wrong sign component → need to distinguish muon charge (or n vs p) in order to measure ν versus ν xsec precisely

● Doping with Gadolinium (0.1%):

(Gd doping will be implemented in SK in next years: stay tuned!)

Limitation: need to model properly the neutron multiplicity in ν and ν events which is affected by initial and final state effects

tag the presence of neutron in the final state

11/14

νµ versus νe

Main limitation is due to statistics: standard neutrino fluxes are dominated by νµ (protons on target → K,π → µνµ)

Measurement of electrons and separation from muons well done in all mentioned detectors: TPC PID (+calorimeters), cherenkov rings

(ν flux from muon decays precisely known)

νµ CCQE: νµ + n → µ- + p

νe CCQE: ν

e + n → e- + p

Neutrinos from Stored Muons (nuSTORM): beams from the decay of 3.8 GeV muons confined within a storage ring

Monitor the production of electrons in standard ν beam: uncertainty on ν

e flux improved by one

order of magnitude

12/14

Alternative concept: NuPRISM

Flux at different off-axis angle = different Eν spectra

Combine measurements at different angles to

● build monochromatic flux → measure xsec vs energy

● build flux shape similar to oscillated flux at far detector

should decrease the ND → FD extrapolation uncertainty but cannot reconstruct the details of the final state (no precise measurement of xsec: µ charge, low momentum hadrons, different targets...)

13/14

The way out? A given cross-section

measurement is affected by many different effects

To disentangle them we need to compare different measurements (C, O, ν species, different variables …)→ long term plan & collaboration btw experiments at different flux

The role of theoreticians is fundamental here !

14/14

Slide credit to Laura Fields

FUTURE EXPERIMENTAL PROGRAM for neutrino cross sections:

BACKUP

Sara Bolognesi (CEA Saclay)

Neutrino energy

We do not know Eν event by event. Eg, SuperK measures the outgoing muon and

infers the neutrino energy on the basis of available ν-nucleus interaction models

9/16

eg: low energy tails due to 2p2h

One possible way out: measure also outgoing proton (or more in general full hadronic final state)

Martini et al

Spreading of reconstructed Eν for

fixed true Eν due to nuclear effects

A-scaling (2)

Importance of large Ar TPC (MicroBooNE, SBND, Captain-Minerva) for DUNE programVery important to have large Ar target in DUNE near detector

Measure on different targets and scale with A relying on models:

most of measurement on C (CH scintillators) and few on iron, lead... but scaling of nuclear effects with A not straightforward. Few examples:

● low energy: scaling of 2p2h contribution depends on fraction of nn / np initial correlated pairs in the nucleus which is not well known

● high energy (Deep Inelastic Scattering): uncertainty on nuclear PDF → A-scaling not well reproduced

strawtubes (filled with HP Ar) with radiators walls (C

3H

6) interleaved

with different targets

DUNE ND reference design:

● a lot of interactions will not be on Ar

● combined analysis: target subtractions etc. → large systematics due (eg) to uncertainties on acceptance due to xsec modeling

→ HP Ar TPC under discussion

7/16

Pions fate

LARIAT: ArgoNEUT repourposed in FNAL charged test beam

Final state effects on pions: very sparse data available

(large potential also from DUNE prototypes at CERN test beam!)

New measurement from DUET experiment at TRIUMF

π+ABS CX π+

inelastic

π+

CHOERENT: three detector technologies at neutron spallation source at Oak Ridge

Xenon double phase

high purity Germanium

Cesium Iodide scintillator

CONNIE: Charged Coupled Device at Angra Nuclear Power Plant (Brasil)

Measure of nuclear recoil in neutral current events

Large xsec (1-100 MeV) but never observed

Coherent eleastic ν-nucleus scattering (CEνNS)

modeling energy transport in SuperNova

SuperNova n detection

irreducible background to Dark Matter

monitoring of neutrino reactors

Cross-sections

T2K flux NOVA flux

3/21

Formaggio, Zeller arXiv:1305.7513

Moving to larger energies ...

T2K flux DUNE

13/21

Moving to larger energies ...

T2K flux DUNE

14/21

Moving to larger energies ...

T2K flux DUNE

Need to control well all different xsec, each process has very different detector acceptance

15/21

2p2h at near and far detector

Near Detector(before oscillation)

Far Detector(after oscillation)

2p2h uncertainty is mainly on the overall normalization at NDwhile at FD 2p2h biases the shape of neutrino energy spectrum (fill the oscillation deep)

CCQE

2p2h

CCQE+2p2h

CC1π

Martini et al

At ND 2p2h is slightly lower muon momentum than 1p1h

… but is also the region where the CC1π background is larger ...

There is no clear enhancement of 2p2h for backward muon angles

muon momentum < 1.2GeV

2p2h: ν vs ν

5

2p2h xsec in ν 2p2h xsec in ν

Eν (GeV) Eν (GeV)

Martini et alNieves et al

Martini et alNieves et al

● Important systematics on oscillation analysis (δCP

measurement) :

2p2h only