Diapositiva 1

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NOW 2008 (5th Neutrino Oscillation Workshop)
Conca Specchiulla 6-13 September 2008
V. Antonelli, G. Battistoni, P. Ferrario1, S.
Forte (Università degli Studi di Milano e
I.N.F.N. Sezione di Milano e 1Università di
Valencia) (Nucl. Phys. B Proc. Suppl. 168 (2007)
192-194 IFAE 2007, pagg.271-274)
Neutrino physics and the Standard Model
Precision measurements with future neutrino
beams
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Standard Model and neutrino physics

• Neutrino (n) interacts only weakly ideal
  candidate to test e.w. interactions
• S.M. and n physics up to now.Parallel history
  since 60s
• - Standard Model strong confirmations
  precision tests (LEP, high energies)
• - n physics. Relevant role in the past
  Gargamelle, discovery of neutral currents
  possible measurement of Weinberg angle proof of
  neutrino masses and mixing need
  to modify Standard Model theories beyond the
  S.M.

Future ?

• Search of physics beyond the S.M., 2 ways
• 1) Higher energy
• 2) High intensity (Low energy tests of S.M.
  search for rare processes measurements of S.M.
  parameters with low E and very high intensity n
  beams)

Fu
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Open Problems in Neutrino Physics

• Despite the relevant recent results,
• Still many open problems
• - Nature of neutrino (Dirac o Majorana)
• Absolute value and hierarchy of masses (direct,
• inverse or quasi-degenere)
• Exact determination of mixing parameters
• ?130 or ?13 ? 0
• - Search for CP violation

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ROLE OF ACCELERATOR n EXPERIMENTS

• Up to now main results from solar and atmospheric
  n. Recent contributions from K2K and MINOS
  (accelerator) and KamLAND (reactor).
• All results from disappearance exp. only claim
  from appearance was LSND disproved by MiniBOONE.
  
• Why ?
• - Solar n scale below kinematical threshold
  for muon production
• - Atmospheric scale nm nt leading
  oscillation . t identification needed, difficult
  task (CNGS)
• nm ne oscillation (suppressed by
  q13 high intensity source needed) . Future
• CNGS (1st run August 2006) search for nt
  appearance , very few events. Possible
  improvement of q13 limit (from 11 to 7)
• The q13 puzzle
• - if q13 10 no need for new accelerators
  
• - if q13 gt than 3 need for new detectors
  (Mton water Cerenkov) and superbeams
• - if q13 1 new generation of experiments
  needed b beams and n factories
• - if q13 lt 1 CP phase not accessible with
  terrestrial experiments

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Future of neutrino physics (from accelerators)

• 1st stage Conventional n beams from a secondary
  meson beam (K2K, MINOS, CERN/G.Sasso, T2K 1st
  phase) and Double Chooz (reactor)
  partial improvement of ?13 Not enough to study
  the leptonic CP violation
• 2nd stage Superbeams (T2K 2nd phase, No?A,
  CERN)
• beam luminosity increase ?13 precise
  measurement and/or (eventual) CP violation
• search
• - T2K (Japan, 2009) 2nd phase ?? beam from
  JParc to SuperK (L295 Km)
• - No?A (USA) use the beam of NuMI at FNAL,
  detector at about 800 Km
• -CERN possible superbeam exploiting the CERN SPL
• 3rd stage (end of next decade) n from primary
  beam decays
• Neutrino factories ? from decay of muons (tens
  of GeV) in accumulation rings
• ( )
• Beta beams ? beams from ? decays?(few GeV or
  lower E)

6He for anti-v beam and 18Ne for ? beams
Example
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WEINBERG ANGLE
Electroweak unification SU(2) x U(1) simmetry
invariance ? weak and e.m. forces mixed
couplings
SU(2) ? g
U(1) ? g
Elas
n-e- elastic scattering competitive for Weinberg
angle measurement at high energy n factories
at lower energies the lower cross sections
compensated by high intensities. For E MN
(quasi) elastic contributions to n-nucleon
interactions are sizable (see figure).
ela
n-
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Neutral current scattering amplitudes
FORM FACTORS introduction
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Weinberg angle determination

• 6 cross sections neutrino (antineutrino) neutral
  currents on proton (neutron) and neutrino
  (antineutrino) charged currents
• Fixing the values of the electric form
  factors there are 6 parameters left Weinberg
  angle and 5 form factors
• (GpM, GnM , GSM , GA , GSA)
• Analytical study System of 6 equations coupled 2
  by 2 The equation for Weinberg angle can be
  solved analytically in terms of measurable
  quantities (cross sections combination and
  kinematical variables)
• Simultaneous fit of Weinberg angle and hadronic
  form factors is feasible.

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Numerical study

• From data analysis simultaneous fit of the values
  of Weinberg angle and hadronic form factors.

• Experimental requirements and caveat
• Select the QE (Quasi elastic) scattering. Elastic
  and quasi elastic cross sections optimal region
  around 1 GeV (ex. T2K)
• Neutral currents must be identified only
  recoiling proton can be measured, no NC on
  neutron from 6 to 4 cross sections, loss
  of information.
• Different Q2 bins should be investigated good
  kinematic reconstruction neeeded.

Detector choice Liquid Argon TPC - Pro in
principle p down to 50 MeV can be identified. -
Con Difficult to assemble a large mass nuclear
reinteractions in Ar are more important than in
water. For p gt 300 MeV Q2 gt 0.1
GeV2 , about 75 of the events surviving.
Measurements at near detector already competive
with detector below kton (around 500 ton)
Interesting possibility, mainly for superbeams
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Numerical analysis and results

• 1st possible approach
• Assume the form factors expressions known and
  perform a simultaneous fit of Weinberg angle and
  hadronic form factors
• -Possible to reach a good level of accuracy
• -Confirmation that the dipole approximation is
  not enough for the magnetic and electric form
  factors of nucleons
• 2 kind of analysis (blind analysis)
• - We make no assumptions on the functional form
  of form factors and riproduce them by means of a
  neural network.
• Studied different possible combinations of form
  factors to fit simultaneously with the Weinberg
  angle
• The network works quite well and the results of
  the fit are satisfactory

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A simple example (1st KIND OF ANALYSIS)

• Simultaneous determination of sin2qW and
  GMS(Q2)

GSA known with bad accuracy (about 30), but
cross sections weekly dependent on GSA. We assume
dipole form and take 1s variation for forward
value GSA(0) -0,13 0.09

• - Using for neutrino energy En 1 GeV
• - Detector 10 ktons Liquid Ar
• - Assuming in data generation sin2qw
  0.2312
• - From simultaneous fit of sin2qw and GMS,
  varying GAS, we get
• sin2qw 0.2309 0.0019 (stat) 0.0024
  (syst)

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Analysis with Neural Network

• Simultaneous fit of sin2qW and magnetic form
  factor GMS (one of the less known)
• The form factor is very well reproduced by the
  neural network
• Accuracy of the angle fit is satisfactory, even
  if it is very sensitive to the value of the
  magnetic form factor.
• Experimental value sin2qW 0.23120
  Result of the fit sin2qW 0.231290.00018
• Simultaneous fit of sin2qW and magnetic form
  factor for proton or neutron (GMP or GMN )
• GMP reproduced quite well (despite some problems
  in low Q2 bins).
• Weinberg angle fit is satisfactory.
• Simultaneous fit of sin2qW and different
  combinations of form factors attention to
  possible correlations and possible existence of
  fake solutions .

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CONCLUSIONS

• Standard Model working very well up to the
  electroweak scale
• Useful to improve parameters knowledge at
  medium-low energies.
• Role of n physics and future experiments with
  high intensity beams
• n(anti-v)-nucleon interactiondependent from
  Weinberg angle and hadronic form fac.
• Analytical study and estimate of accuracy in
  sin2?W determination
• Numerical analysis of the problem
• Examples b beams and superbeams potentiality
• Measurements realistic with present Icarus
  technology
• Examples of numerical analysis
• assuming a known functional form for hadronic
  form factors
• with no assumptions on hadronic form factors
• Measurement at energies low with respect to LEP
  is interesting to
• verify theory consistency and/or eventual signals
  of physics beyond S.M.

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Beta-Beams
PRO

• Only 1 flavor in the beam
• Well known and determined energy (kinematics
  well known
• and nucleon recoil negligible)
• Beams well collimated and with value of (?/ECM)
  higher than
• ? factories

• Proposals
• - Cern- Frejus (L about 130 Km low beam E)
• - Higher E beams and longer baselines
  (Cern-G.Sasso/Canarie)

• proposed for neutrino physics, but useful also
  to study Standard
• Model ?

• Analysis already available for neutrino
  factories

Interesting to extend it to beta-beams
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T2K

• Neutrino beam from protosinchrotron of 50 GeV,
  0.75 MW at JParc
• Off-axis beam to SuperKamiokande (L 295 Km) .
  Begins spring 2009
• Main goals
• - sin2 ?13 measurement with sensitivity 20 times
  better than Chooz
• Measurement of ?m232 and sin2 ?23 (atmospheric
  parameters) at 1-2
• (?? disappearance)
• - search?for sterile ? (weak currents
  disappearance)
• Tests of Standard Model parameters low
  energy measurements, different from LEP eventual
  possibility of signals of new physics

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Beta-Beams
PRO

• Only 1 flavor in the beam
• Well known and determined energy (kinematics
  well known
• and nucleon recoil negligible)
• Beams well collimated and with value of (?/ECM)
  higher than
• ? factories

• Proposals
• - Cern- Frejus (L about 130 Km low beam E)
• - Higher E beams and longer baselines
  (Cern-G.Sasso/Canarie)

• proposed for neutrino physics, but useful also
  to study Standard
• Model ?

• Analysis already available for neutrino
  factories

Interesting to extend it to beta-beams
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Detector alternatives

• Water Cherenkov
• Pro there is the possibility of assembling a
  very large mass (some MTon)
• Con the Cherenkov threshold prevents the
  detection of recoiling protons with plt1 GeV.

2) Liquid Argon TPC Pro in principle p down to
50 MeV can be identified. Con Difficult to
assemble a large mass nuclear reinteractions in
Ar are more important than in water For p gt 300
MeV Q2 gt 0.1 GeV2 , about 75 of the
events surviving. Measurements at near detector
already competive with detector below kton
(around 500 ton)

Interesting possibility mainly for superbeams