Near Detector Working Group for ISS Near Detector Working Group for ISS Near Detector Working Group for ISS Near Detector Working Group for ISS

Neutrino Factory Scoping Study Meeting

24 January 2006Paul Soler

University of Glasgow/RAL

Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006

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ContentsContents

1. Near Detector Aims2. Organisation3. Flux measurement and control4. Muon polarization5. Cross-sections6. Charm production7. Possible technologies

Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006

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1. Near detector aims1. Near detector aims Control of the systematics for the long baseline oscillation measurement

– Flux measurement and control – Neutrino beam angle and divergence– Beam energy and spread– Control of muon polarization

Near detector neutrino physics:– Neutrino cross-section measurements (DIS, QES, RES scattering)– Determination of charm production spectra for background studies at far

detector– Parton Distribution Functions (polarized and unpolarized?)– Other physics:

• sin2W - sin2W ~ 0.0001 S from xF3 - S~0.003• D0/ D0bar mixing• polarization• ….

Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006

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2. Organisation2. Organisation What has been done so far?

– Set up webpage: http://ppewww.ph.gla.ac.uk/~psoler/near_detector.html – I have contacted an ad hoc group of people from different communities:

theoreticians interested in near detector physics (eg. PDFs …), experimentalists working on near detectors at neutrino experiments, …

– List can be found on webpage: not exhaustive, so please contact me if you would like to be included.

– Not much else! What (I think) needs to be done?

– Set-up a generic simulation of a near detector– Define a series of potential detector geometries to run on near detector– Carry out physics studies needed for the ISS report:

1. Study flux normalisation through: 2. Use quasi-elastic and elastic interactions to determine neutrino spectrum3. Reconstruct muon polarization from spectrum4. Sensitivity for cross-section measurements: low energy?5. Determination of charm: remember this is main background for golden channel!6. ….suggestions ….

ee

Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006

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3. Flux normalisation 3. Flux normalisation

e

e

e

e

Neutrino beams from decay of muons:

Spectra at Production (e.g. 50 GeV) Number CC interactions

Polarisation dependence

P=+1: gone!

Need to measure polarization!!

Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006

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3. Flux normalisation (cont.)3. Flux normalisation (cont.)

Rates:— E = 50 GeV

— L = 100 m, d = 30 m— Muon decays per year: 1020

— Divergence = 0.1 m/E

— Radius R=50 cm

100 m

Yearly event rates

High granularity in inner region

that subtends to far detector.

E.g. at 25 GeV, number neutrino

interactions per year is:

20 x 106 per 100 g/cm2.

With 50 kg 109 interactions/yr

Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006

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3. Flux normalisation (cont.)3. Flux normalisation (cont.) Neutrino flux normalisation by measuring: Signal: low angle forward going muon with no recoil Calculable with high precision in SM

Same type of detector needed for elastic scattering on electrons:

ee

)LABin(2)( 2

22

22

EmG

mq

msG

dy

edeF

W

WFCC

ee ee

)()(

ee )()(

)1(22 ymE ee E.g. CHARM II obtained value of sin2W from this

24

22

2

)1(sinsin2

1)(y

sG

dy

edWW

FNC

24

22

2

1sinsin2

1)(y

sG

dy

edWW

Fe

Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006

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4. Muon polarization4. Muon polarization Fit neutrino spectrum for polarization:

Compare fitted polarization to measured one from polarimeter:

Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006

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5. Cross sections5. Cross sections

Measurement of cross sections in DIS, QE and RES. Coherent Different nuclear targets: H2, D2

Nuclear effects, nuclear shadowing, reinteractions

With modest size targets can obtain very large statistics

What is lowest energy we can achieve? E.g. with LAr can go down to ~MeV

Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006

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6. Charm Production6. Charm Production Remember that main background to golden

channel is production of charm: Qt = P sin2 cut eliminates backg at 10-6

...,,,, 00 csDDDD

not detected

De

e

De e

NC

CC

Hadron decay

Can use near detector to measure Pt and Qt distribution of charm, if we can reconstruct explicitly:

With silicon detector can reconstruct more than 106 charm states per year

Cervera et al.

Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006

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6. Charm (cont.) 6. Charm (cont.) NOMAD-STAR silicon detector was able to reconstruct 45 charm

events in NOMAD. Measured charm rate:

Fully active silicon target (ie. 52 kg with 18 layers of Si 500 m thick,

50 x 50 cm2 =4.5 m2) for full charm event reconstruction. Optimal design: fully pixelated detector (e.g. Monolithic Active Pixels MAPS)

Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006

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7. Possible technologies 7. Possible technologies Apart from silicon, there are other possibilities: Liquid argon TPC in a magnetic field would be able to perform as a near

detector as well. Can it withstand the rate?

Scintillating fibre tracker Scintillator (like Minerva) Standard gas TPC (like T2K near detector) …. Need to develop proper simulation to compare options.

2.5 GeV e, 1.5T