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Oscillation Physics at INO
Debasish Majumdar (On behalf of INO collaboration) Saha Institute of Nuclear Physics Kolkata Sattelite workshop on INO, IITB, Mumbai, 1-2 Aug. 2005
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India-based Neutrino Observatory
An underground facility in India for neutrino physics The proposed detector is an Iron CALorimeter (ICAL) detector ICAL consists of iron plates stacked horizontally interleaved with glass RPC detectors
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Purpose of INO To see the actual oscillation of neutrinos
Study of matter effects through electric charge identification To identify the mass hierarchy (normal or inverted) To measure the 13 mixing angle 13 Study of CP and CPT violation A) Study atmospheric neutrinos B) End detector of a long base-line experiment
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P() = 1 - sin22 sin2 [1.27 m2 (L/E)]
For 3- Flavours cij=cos ij sij =sin ij For 2- Flavours P() = 1 - sin22 sin2 [1.27 m2 (L/E)]
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Two flavour oscillation formula:
P() = 1 - sin22 sin2 [1.27 m2 (L/E)], L in Km, E in GeV For oscillation studies one should have L the path-length of the E the energy of the +Z d R L L = (R-d)cos2() + [R2 - (R-d)2sin2()]
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In the absence of oscillation Up-going events = Down going events
P() = 1 - sin22 sin2 [1.27 m2 (L/E)], In the absence of oscillation Up-going events = Down going events In presence of oscillation Down-going neutrinos suffers no or negligible oscillation [as they traverse shorter length (L)] Up-going neutrinos traverse longer length (L) Oscillates effectively plot shows oscillatory behaviour
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Mirroring of down going events
For no oscillation Down going Down going events in any direction Up going events from opposite direction True L Detector Due to oscillation Up going events < down going events in the opposite direction - Earth + Atm L= mirrored L Up going “Mirror” down going ’s with angle - consider them no oscillation standard for up going ’s at angle Measure of oscillation
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Detector Configuration
Horizontal alignment : (ICAL-H) No. of Chambers = 8 along y axis No. of Modules = 16 along x axis No. of Layers = 140 along z axis Dimension : 32m 16m 12m Mass = 32 kTon For 100 kTon Horizontal stacking dimension is changed as x = 96m, y = 16m, z = 12m
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SIMULATIONS WITH ICAL DETECTOR a) NUANCE event generator Given the detector specifications and atmospheric neutrino flux (Burtol and/or Honda) it generates neutrino events at ICAL (product particles and their production vertex at ICAL) b) GEANT 3.2 Simulation Code The outputs of NUANCE are the inputs to GEANT GEANT propagates the product particles through ICAL and Gives as outputs, their hit points, momenta, time information etc. c) Analyse the GEANT output
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Case I: Oscillation incorporated inside NUANCE itself
GENERATING OSCILLATED EVENTS USING NUANCE Output details : Event no., particle id, x, y, z, px, py, pz Oscillation probability P() = 1 - sin22 sin2 [1.27 m2 (L/E)], m2 =2.0 10-3 eV2, sin22 =1 Case I: Oscillation incorporated inside NUANCE itself Case II: From NUANCE output , prob. of each event is calculated using the oscillation formula Now after each event call a random number. If prob.> Random number, then that event survives. If prob.< Random number, then that event is ignored Resulting Output is Oscillated Nuance Data
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SIMULATION USING GEANT 3.2 CODE
A GEANT based simulation programme is written A 3-D cartesian coordinate system is used with Origin at the centre of ICAL Z-axis pointing upwards Detector dimensions -1600 cm < x < cm -800 cm < y < +800 cm -600 cm < z < +600 cm (32 m x 16 m x 12 m) Magnetic Field Bx = 0 = By, Bz = 1 Tesla Programmes are also written to read a mapped magnetic field in x-y plane (Bx, By, 0) and use it for GEANT simulation Contd….
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Output of GEANT based simulation programme
Co-ordinates of the successive hit points and their momenta at every hit point (i.e. x,y,z, px, py, pz) of the product particles (mainly ’s and hadrons), propagating through ICAL) From (x,y,z) coordinates tracks (trajectories) are constructed Trajectories are helical for charged particles (due to B) with continuously shrinking radius due to energy loss Y (cm) Y (cm) X (cm) X (cm)
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Finding L and E of incident from GEANT simulated tracks
Two types of analyses Analysis with fully contained (FC) events only Analysis with both FC and partially contained (PC) events L is calculated by finding the zenith (polar angle) L = (R-d)cos2() + [R2 - (R-d)2sin2()] is calculated from the track and it’s projection on x-y plane Energy E is calculated in two ways FC events From average path length FC + PC events Using the track geometry (bending due to magnetic field B)
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Track Selection FC events
i) A neutrino event must have a track with 12 hits or more ii) The event has no more than two tracks FC + PC events Number of hits > 9 Zenith angle cuts L/E Resolution We define Resolution function in terms of (L/E)reso = {(L/E)true – (L/E)ex}/(L/E)true Where, L/E(true) : Parameter estimated from the NUANCE output only () L/E(exp) : Parameter estimated after passing through GEANT
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Up/Dn vs L/E plot showing oscillation
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Up/Dn vs L/E plot showing oscillation
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Resolution Plots
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Resolution Plots
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Resolution Plots
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Extraction of oscillation parameters through 2 analysis
The 2 is defined as, 2= {[(Up/down)theory – (Up/Down)Expt.]/Error}2 Theory: Data obtained from NUANCE output folded with resolution. Expt.: Results obtained from GEANT simulation.
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Contour Plot
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Contour Plot
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Oscillation Physics at INO with 3 ’s
(Three mixing angles and two mass square differences) INO will address Observance of oscillation and precise measurement of oscillation parameters (study of matter effects) Sign of Determination of Probing CP violation STUDY A) Atmospheric Neutrinos B) Neutrinos from neutrino factories
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3 Direct (Normal) hierarchy atm 32 > 0 2 solar ij = mij 1 2 solar 1 atm Inverted hierarchy 32 < 0 3
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For 32 0, For neutrinos For anti-neutrinos For 32 0, just the reverse
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Determination of sign of 32
(From matter induced asymmetry) AN is different for normal mass hierarchy (32 > 0) and inverted mass hierarchy (32 < 0)
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Probing neutrino beam from neutrino Factories
( ICAL as end detector of long baseline experiment) Beam from storage rings with long straight sections Intense, high luminosity neutrino beams from decaying in the straight section , Look for wrong sign Sign of 32 Determination of 13 Probing CP violation in the leptonic sector
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PUSHEP Magic baseline ~ 7250 km (No CP) Rammam JHF (4828) JHF (6556)
CERN (6871) CERN (7145) FERMILAB (10480) FERMILAB (11300) Magic baseline ~ 7250 km (No CP)
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Wrong sign events vs 32 For small 13 and 32 > 0 e enhanced
Baseline from JHF (A~ E/ 32)
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The achievable sin13 at INO vs threshold energy of detection
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The ratio of wrong sign events and opposite sign events for the
storage ring vs base length Probing CP vs
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Discussions 1) INO has the potential to measure oscillation dip
and the oscillation parameters 2) ICAL at INO is capable of probing the measure of 13 and sign of 23 from atmospheric neutrinos 3) ICAL at INO can be a very effective far end detector for long baseline experiments 4) With its charge discrimination capability ICAL at INO can be very efficient to determine not only oscillation but also mixing angle 13 and the mass hierarchy (thus substantiating the atmospheric neutrino measurements) And most importantly 5) Probing the CP violation-the holy grail of Physics in the lepton sector
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INO marches ahead Have a good day
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