Near Detector Report

Near Detector ReportNear Detector ReportNear Detector ReportNear Detector Report

International Scoping StudyDetector Meeting

4 July 2006Paul Soler

University of Glasgow

International Scoping Study CERN, 4 July 2006

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ContentsContents

1. MINOS near to far ratio methods2. Beam diagnostics3. Near Detector flux and event rates4. Near Detector design5. R&D plans


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1. MINOS Near to Far Ratio Methods1. MINOS Near to Far Ratio Methods

Prediction far detector spectrum from near Prediction far detector spectrum from near detectordetectorLook for a deficit of νμ events at Far Detector

Unoscillated

Oscillated

νμ spectrum

Monte Carlo

Monte Carlo

ν ν 22

21 ssin inm L

PE

θΔ

μ μ

Spectrum ratio

The Million $ Question: How to predict the Far Detector spectrum?

Last ISS meeting: talk by Weber


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Problems– Hadron production uncertainties

– Cross-section uncertainties

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2 2 2

1 11

FluxL γ θ

2 2

0.431

EE πν

γ θ

Three beams in MINOSThree beams in MINOS

Near and Far Detector energy spectra are not identical

– Both detectors cover different solid angles

– Near Detector sees extended line source

f

to FarDetector

Decay Pipe

(soft)

(stiff)

n

target

ND2

2 2 2

1 11

FluxL γ θ



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Four possible methods for beam flux extrapolation

– NDFit method– 2D Grid method– Near to far ratio– Beam matrix method

NDFit: Reweighting hadronic distributions

LE-10/185kA pME/

200kApHE/200kA

Weights applied as a function of hadronic xF and pT.LE-10/

Horns off

Not used in the fit

LE-10 events



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2D Grid method

– Bin data in reconstructed Eν & y

– Fit weight as a function of true Eν & y

Near to far ratio– Look at differences between data and MC in Near

Detector as a function of reconstructed Energy

– Apply correction factor to each bin of re-constructed energy to Far Detector MC: c = ndata / nMC

Beam matrix– It uses the measure Near Detector distribution and

extrapolates it using a BEAM Matrix to the Far Detector.



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Predictions for far detector do not

give perfect agreement but well

controlled.

Four methods agree very well– Different systematics

Predicted FD true spectrum from the Matrix Method

Predicted spectrum

Nominal MC

0.931020 POT



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Flux determination at a neutrino factory (Blondel)

2. Beam Diagnostics2. Beam Diagnostics

polarization controls e flux:

+ -X> e in forward direction

Main parameters to MONITOR 1. Total number of muons circulating in the ring: BCT, near detector for purely leptonic processes 2. muon beam polarisation, polarimeter 3. muon beam energy and energy spread, race-track or triangle. NO BOW-TIE! +polarimeter 4. muon beam angle and angular divergence. straight section design +beam divergence monitors e.g. Cerenkov? 5. Theory of decay, including radiative effects OK

We believe that the neutrino flux can be monitored to 10-3 IF+ design of accelerator foresees sufficient diagnostics. + quite a lot of work to do to design and simulate these diagnostics.


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2. Beam Diagnostics2. Beam Diagnostics Beam Current Transformer (BCT) to be included at entrance of

straight section: large diameter, with accuracy ~10-3.

Beam Cherenkov for divergence measurement? Could affect quality of beam.

storage ring

shielding

the leptonic detector

the charm and DIS detector

Polarimeter

Cherenkov

BCT


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2. Beam Diagnostics2. Beam Diagnostics Muon polarization:

Build prototype of polarimeter

Fourier transform of muon energy spectrum

amplitude=> polarization

frequency => energy

decay => energy spread.


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3. Near Detector Beam Flux3. Near Detector Beam Flux

Near detector(s) are some distance (d~30-1000 m)

from the end of straight section of the muon storage ring. Muons decay at different points of straight section: near detector is

sampling a different distribution of neutrinos to what is being seen by the far detector

storage ring

shielding

the leptonic detector

the charm and DIS detector

Polarimeter

Cherenkov d

Different far detector baselines:B 730 km, 20 m detector: ~30 radB 2500 km, 20 m detector: ~8 radB 7500 km: 20 m detector: ~3 rad

If decay straight is L=100m and

d =30 m, at 8 rad, lateral

displacement of neutrinos is

0.25-1.0mm to subtend same angle.


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3. Near Detector Beam Flux3. Near Detector Beam Fluxd=30 m, r=0.5 m

Fluxd=130 m, r=0.5 m d=1km, r=0.5 m

e

Anti

17.8 GeV

15.3 GeV

21.6 GeV34.1 GeV

29.2 GeV18.5GeV

Neutrino point source (muon decays not taken into account)


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3. Near Detector Event Rates3. Near Detector Event Ratesd=30 m, r=0.5 m

Event ratesd=130 m, r=0.5 m d=1km, r=0.5 m

Anti

e

25.5 GeV

22.3 GeV

26.6 GeV 37.1 GeV

32.5 GeV

23.2 GeV


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3. Near Detector Event Rates3. Near Detector Event RatesCompared to far detector: d=2500 km, r=20 m

Event rates

Anti

e

35.8 GeV

30.0 GeV

38.1 GeV

33.3 GeV

Flux

ND at 1 km has similar spectra to FD


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4. Near Detector Design4. Near Detector Design Overall design of a near detector

B Vertex detector: Choice of Pixels; eg. Hybrid pixels, Monolithic Active Pixels (MAPS), DEPFET; or silicon strips.

B Tracker: scintillating fibres, gaseous trackers (TPC, Drift chambers, …)B PID: B CalorimeterB Muon ID

Old UA1/NOMAD/T2K magnet offers a large magnetised volume with a well known dipole field up to 0.7 T.

Use NOMAD/T2K as basis for design


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4. Near Detector Design4. Near Detector Design

VERTEX DETECTOR

Dipole Magnet: 0.4-0.7 T

Tracker (SciFi or TPC?)

ElectromagneticCalorimeter PID

HadronicCalorimeter

Nuclear Target


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4. Near Detector Design4. Near Detector Design Vertex detector

B Identification of charm by impact parameter signatureB Charm has similar decay time to tau particle search used in NOMAD-STAR


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4. Near Detector Design4. Near Detector Design Longest silicon microstrip

detector ladders ever built: 72cm, 12 detectors, S/N=16:1

Detectors: Hamamatsu FOXFET p+ on n, 33.5x59.9 mm2, 300 m thick, 25 m pitch, 50 m readout

VA1 readout: 3 s shaping

NOMAD-STAR


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CC event

Primary vertex

Secondary vertex

NOMAD-STAR


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4. Near Detector Design4. Near Detector Design Vertex resolution: y = 19 m Impact parameter resolution: 33 m

Double vertex resolution: 18 m from Ks reconstruction

Pull:~1.02

x~33 m

x~18 m z~280 m

Point resolution: 6 m


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4. Near Detector Design4. Near Detector Design Charm event selection:

Efficiency very low: 3.5% for D0, D+ and 12.7% for Ds

+ detection because fiducial volume very small (72cmx36cmx15cm), only 5 layers and only one projection.

From 109 CC events/yr, about 3.1x106 charm events, but efficiencies can be improved.


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Passive target can provide target mass, but affects vertex and tracking reconstruction efficiency due to scatters

Improve efficiency by having 2D space point measurement and more silicon planes.

For example: 52 kg mass can be provided by 18 layers of Si 500 m thick, 50 x 50 cm2 (ie. 4.5 m2 Si) and 15 layers of B4C, 5 mm thick

Optimal design: fully pixelated detector (could benefit from Linear Collider developments in MAPS, DEPFET or Column Parallel CCD). With pixel size: 50 m x 400 m 200 M pixels, ~0.4 X0

Could also use silicon “3D” detectors or double sided silicon strips (with long ladders of 50 cm x 50 m 360 k pixels).

Will start R&D on MAPS and DEPFET at Glasgow from October this year – MI3 collaboration (MAPS) & Bonn University (DEPFET)


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5. Near Detector R&D Plans5. Near Detector R&D Plans

What needs to be measured:

1) Number of muons in ring (BCT)

2) Muon beam polarisation (polarimeter)

3) Muon beam angle and angular divergence (Cherenkov, other?)

4) Neutrino flux and energy spectrum (Near Detector)

5) Neutrino cross-sections (Near Detector)

6) Backgrounds to oscillations signal (charm background, pion backgrounds, ….), dependent on far detector technology and energy.

(Near Detector)

7) Other near detector physics: PDF, electroweak measurements, ….

ee


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5. Near Detector R&D Plans5. Near Detector R&D Plans R&D programme1) Vertex detector options: hybrid pixels, monolithic pixels (ie. CCD, Monolithic

Active Pixels MAPS or DEPFET) or strips. Synergy with other fields such as Linear Collider Flavour Identification (LCFI) collaboration.

2) Tracking: gas TPC (is it fast enough?), scintillation tracker (same composition as far detector), drift chambers?, cathode strips?, liquid argon (if far detector is LAr), …

3) Particle identification: dE/dx, Cherenkov devices such as Babar DIRC?, Transition Radiation Tracker?

4) Calorimetry: lead glass, CsI crystals?, sampling calorimeter?

5) Magnet: UA1/NOMAD/T2K magnet?, dipole or other geometry?

Collaboration with theorists to determine physics measurements to be carried out in near detector and to minimise systematic errors in cross-sections, etc.


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5. Near Detector R&D Plans5. Near Detector R&D Plans Request plan :

40k/yr

40k/yr80k/yr

80k/yr

120k/yr

120k/yr


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ConclusionsConclusions There is important synergy between existing (or planned) experiments

such as MINOS and T2K and the technology for future near detectors. Cross-sections and fluxes remain an issue. Learning the techniques that these experiments are adopting helps to formalise the problem that we will face at a neutrino factory.

A near detector at a neutrino factory needs to measure flux and cross-sections with unprecedented accuracy. Beam diagnostic devices need to be prototyped

It is worth noting that the beams measured by a near detector if it is close to straight sections (<100m) are quite different from far detector. However, at 1 km, beams start to look very similar.

We should start having some idea of what a near detector should look like. One proposal is to use the old UA1 magnet (like in NOMAD and T2K) once more.

The near detector should have a vertex detector, tracking planes, particle identification, calorimetry and muon identification. The dipole filed between 0.4-0.7 T can provide good muon momentum resolution.

R&D plans are not very well defined at the moment

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