Transcript EuroNu_Near_Detector_Soler - Indico

Near Detector Tasks
EuroNu Meeting, CERN
26 March 2009
Paul Soler
Near Detector and Beam Diagnostics aims
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Beam diagnostics (needed for flux measurement) – Neutrino Factory
– Number of muon decays
– Measurement of divergence
– Measurement of Muon polarization
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Near detector measurements needed for neutrino oscillation systematics:
– Flux control for the long baseline search.
– Measurement of charm background – also search for taus from NSI?
– Cross-section measurements: DIS, QES, RES scattering
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Other near detector neutrino physics (electroweak and QCD):
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sin2W - sin2W ?
Unpolarised Parton Distribution Functions, nuclear effects
Polarised Parton Distribution Functions – polarised target
Lambda (L) polarisation
S from xF3 - S?
_
Charm production: |Vcd| and |Vcs|, CP violation from D0/ D0 mixing?
Beyond SM searches – (taus?)
EuroNu Meeting, CERN
…
26 March 2009
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Beam Diagnostics (ISS report)
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Beam Current Transformer (BCT) to be included at entrance of
straight section: large diameter, with accuracy ~10-3.
Cherenkov
BCT
shielding?
Polarimeter
Radiation
simulations
the charm and DIS detector
the
leptonic detector
storage ring
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Beam Cherenkov for
divergence measurement?
Could affect quality of
beam.
EuroNu Meeting, CERN
26 March 2009
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Beam Diagnostics (ISS report)
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Muon polarization:
Build prototype of polarimeter
Fourier transform of muon energy spectrum
amplitude=> polarization
frequency => energy
decay => energy
spread.
EuroNu Meeting, CERN
26 March 2009
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Flux Measurement at Near Detector
 Best possibility: Inverse Muon Decay scattering off electrons in the near
detector
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
νe + e  ν μ + μ
  + e   e + μ 
Well known cross sections in Standard Model (with 0.1% accuracy)
2
F
s  m 
2 2
μ
G
π
s
2 2
2

s

m
2GF
1

μ 

σ ( e e ) =
E
E
+
E
E

e
μ
ν1 ν2 
2
π
s
3


σ (  e  ) =
EuroNu Meeting, CERN
26 March 2009
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Flux Measurement at Near Detector
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Energy spectra for νμ (green) and anti νe (blue) for 1021  decays/year,
Mass ~1 ton, 400 m long section.
E = 40 GeV.
  + e  e + μ 
E = 40GeV , P = 1
E = 40GeV , P = -1
E = 30GeV , P = 1
E = 30GeV , P = -1
E = 20GeV , P = 1
E = 20GeV , P = -1
νe + e   ν μ + μ 
6.87x105
5.81x105
1.67x106
6.97x104
2.02x105
1.97x105
5.89x105
1.60x104
CERN
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1.83x104 EuroNu Meeting,
1.14x10
26
March
2009
7.83x104
7.76x102
N
1.92x109
2.81x109
1.32x109
1.91x109
8.07x108
1.14x109
Need to redo:
• E=25GeV
• Baseline
storage ring
straight section
(755 m)
• Perform proper
event selection
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Flux Observed by Near Detector
 Near Detector sees a line source (755 long decay straight)
 Far Detector sees a point source

ND
1 km
ND
130 m
e
ND
130 m

e
ND
1 km
EuroNu Meeting, CERN
26 March 2009

FD
2500 km
e
FD
2500 km
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Near Detector flux used to extract Pe
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Original idea: use matrix method with Near Detector data (even if spectrum
not identical in near and far detector!) to extract oscillation probability:
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P e   M 21 MM1 M nOsc
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Two matrix inversions!
Where: M1=matrix relating event rate and flux of e at ND (x-section + det)
M2=matrix relating event rate and flux of  at FD (x-section + det)
M=matrix relating measured ND e rate and FD  rate (measured!)

MnOsc=matrix relating expected e flux from ND to FD
(extrapolation)
Method works well
but two inversions
affects fit convergence
Probability of oscillation
determined by matrix
method under
“simplistic” conditions.
Need to give more
realism to detector and
matter effects.
EuroNu Meeting, CERN
26 March 2009
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Near Detector flux used to extract Pe
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Now we calculate in stages: ND simulated data to predict ND flux
1
sND/E ~35%/√E
ND ,predict  M1` NND
where: M1=matrix relating event rate and flux of e at ND
Extrapolate ND flux to FD: MnOsc=matrix relating e flux from ND to FD
 FD  M nOsc  ND ,predict
Extract FD interaction rate: NFD  M2P e  FD
No oscillations
M2=matrix relating event rate and flux of  at FD, sFD/E ~55%/√E
P e  = prob oscillation
Assume
Flux
from“true”
ND flux
• There is only one matrix
inversion and fit to Pe
seems to be more robust.
• Hardly any change in
error contours by adding
ND information.
• Still need to extract syst
error from method
EuroNu Meeting, CERN
26 March 2009
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Charm measurement
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Motivation: measure charm cross-section to
validate size of charm background in wrong-sign
muon signature
Charm cross-section and branching fractions
poorly known, especially close to threshold
CHORUS
2008
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Semiconductor vertex detector
only viable option in high
intensity environment (emulsion
too slow!)
EuroNu Meeting, CERN
26 March 2009
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Cross section measurements
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Measure of cross sections in DIS, QE and RES.
Coherent p
Different nuclear targets: H2, D2
Nuclear effects, nuclear shadowing, reinteractions
What is expected crosssection errors from
MiniBoone, SciBoone,
T2K, Minerva, before
NUFACT?
At NUFACT, with modest
size targets can obtain very
large statistics, but is <1%
error achievable?
EuroNu Meeting, CERN
26 March 2009
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Other physics: Parton Distribution Functions
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Unpolarised and Polarised
Parton Distribution Functions
S from xF3
Sum rules: e.g. Gross-Llewelyn
Smith
L polarization: spin transfer from
quarks to L
— NOMAD best data
— Neutrino factory ~1000 times
more data
EuroNu Meeting, CERN
26 March 2009
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Near Detector Design
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Overall design of near detector(s): more than one detector?
– Near Detector could be a number of specialised detectors to perform
different functions (ie. lepton and flux measurement, charm
measurement, PDFs, etc.) or larger General Purpose Detector
EM calorimeter
Hadronic
Calorimeter
Muon chambers
EuroNu Meeting, CERN
26 March 2009
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Near Detector Design
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Near Detector elements:
– Vertex detector: Choice of Pixels (eg. Hybrid pixels, Monolithic Active
Pixels …) or silicon strips
– Tracker: scintillating fibres, gaseous trackers (TPC, Drift chambers, …)
– Other sub-detectors: PID, muon ID, calorimeter, …
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Tasks:
– Simulation of near detector and optimisation of layout: benefit from
common software framework for Far Detector
– Flux determination with inverse muon decays, etc.
– Analysis of charm using near detector
– Determination of systematic error from near/far extrapolation
– Expectation of cross-section measurements
– Test beam activities to validate technology (eg. vertex detectors)
– Construction of beam diagnostic prototypes
EuroNu
Meeting,
CERN with theory community
– Other physics studies: PDFs,
etc.
(engage
14 for
26 March 2009
interesting measurements)