A study on different configurations of Long Baseline Neutrino Experiment

Transcription

1 A study on different configurations of Long Baseline Neutrino Experiment Mehedi Masud HRI, Allahabad (With V.Barger, A.Bhattacharya, A.Chatterjee, R.Gandhi and D.Marfatia Phys.Rev. D89 (2014) 1, and arxiv: )

2 What is LBNE? A proposed Long Baseline Neutrino Experiment Beam is sent through earth along a baseline of 1300 Km

3 Physics questions to be tackled by LBNE Mass hierarchy (MH): Normal hierarchy (Δm 31 2 > 0) or Inverted hierarchy (Δm 31 2 < 0) Octant degeneracy for θ23 : Higher octant (θ 23 > 45 ) or Lower octant (θ 23 < 45 ) CP violation (CPV) due to δcp Other physics studies: Supernova neutrinos, proton decay etc..

4 Our Objective Study sensitivity of LBNE to MH, octant and CPV for different possible cases: 1. Keeping the far detector (FD) on surface or taking it underground (thus bringing atmospheric neutrinos into account) 2. Augmentation of the FD with a near detector (ND) 3. Increase of the mass of the FD 4. Change of beam power of the LBNE source 5. Magnetisation of the FD volume 6. Sensitivity to the precision of the measured value of θ 13 ( 8.93 ) 7. Addition of data from NOvA and T2K experiments

5 Long baseline Analysis (Using GLoBES) 120 Gev 700 kw beam with 1300 km baseline Energy bin : 1 10 Gev each of 1 Gev width 5 years neutrino + 5 years anti-neutrino running Channels : ν e appearance & ν μ disappearance ND(Near Detector) systematics : ν e : 1% signal & 1% background ν μ : 1% signal & 5% background NND(No Near Detetor) systematics : ν e : 5% signal & 10% background ν μ : 5% signal & 45% background

6 Combined Analysis We sum the fixed parameter χ 2 obtained from Atmospheric and long baseline analysis in our C++ code Marginalization was done over the parameters θ13, θ 23, Δm 31 2, δ CP Multi-minimization was done in the parameter space to get the minimized χ 2

7 MH & 350 kt-yr FD (unmagnetized) MH sensitivity as a function of true δ CP. Magnetized 350 kt-yr LiAr FD

8 Effect of magnetisation on MH

9 Exposure analysis for MH

10 Mass Hierarchy : Conclusion (Atm + Beam) with ND gives best sensitivity as expected The effect of ND is most pronounced in the favourable δcp region Atmospheric contribution increases sensitivity slightly, but not important because beam itself resolves over 5σ (or 3σ, in case of 100 kt-yr exposure) for all values of true δ CP for 350 kt-yr exposure For a beam only analysis a 3σ determination of MH is possible for any value of δ CP in about 50 kt-mw-yr exposure Inclusion of NOvA and T2K provides minor improvement for hierarchy

11 CP Violation (unmagnetized 350 kt-yr FD)

12 Exposure analysis for CP violation

13 CP Violation : Conclusion Negligible atmospheric contribution: magnetisation of the FD volume does not affect CPV Beam only analysis with ND is better than the combined one without ND. For CPV, using an ND is a better option than taking the FD underground 350 kt-yr exposure lifts the sensitivity to above 3σ for a significant range of δ CP Exposure curves get saturated: CP violating effects cannot be probed for more than about 80% region of the δ CP parameter space

14 Octant degeneracy (unmagnetized 350 kt-yr FD)

15 Octant Sensitivity & θ 13 prior Octant sensitivity as a function of true δ CP for a magnetized 100 kt-yr LiAr FD. Thick lines : σ(θ 13 ) = 0.05sin 2 (2θ 13 true) Thin lines : σ(θ 13 ) = 0.01 Significant improvement on octant sensitivity with increasing precision in the measurement of θ 13

16 Exposure analysis for LO

17 Octant Sensitivity : Conclusion The improvement on combining atmospheric data is more pronounced in NH than in IH Beam only analysis with ND gives roughly smilar sensitivity of combined analysis without ND The more precise the measurement on θ13, the better the sensitivity to octant degeneracy

18 Summary MH can be determined with 350 kt-yr exposure, to a high significance using beam analysis alone For CP violation, augmentation of ND gives significantly better sensitivity For octant also, ND has a substantial effect on sensitivities

19 Thank You!

20 Backup

21 Atmospheric Analysis Standard binned fluxes(honda et. al.) are used Energy bin : 1 10 Gev each of 1 Gev width Cosθ bin : 18 bins, [-1.0, -0.1] μ events: distinguish between particle and anti-particle events over all energies e events: 20% discrimination till 5 GeV, no discrimination thereafter Resolution functions are integrated over Em and Ω m by Gaussian Quadrature Integration over Et and Ω t are carried out by VEGAS Monte Carlo algorithm in our C++ code

22 Atmospheric Analysis Uncertainties : Flux(20%), Cross Section(10%), Zenith angle(5%), Tilt(5%), Overall Systematics(5%)

23 Beam Analysis Comparison Left : LBNE 2010 interim report Right: Our result using same flux

24 Mass Hierarchy(MH) & true θ 13 (Magnetised 100 kt-yr FD) MH sensitivity as a function of true θ 13 for a magnetised 100 kt-yr LiAr FD. The beam power is 700 kw Combined without ND does better than beam only with ND

25 MH & 100 kt-yr FD (unmagnetized) MH sensitivity as a function of true δ CP for un-magnetised 100 kt-yr LiAr FD

26 Exposure analysis for HO

27 CP Violation & enhanced beam (2.3 MW) CP violation sensitivity as a function of true δ CP with enhanced beam power(2.3 MW) for magnetized 100 kt-yr LiAr FD.Comparison Beam only analysis Sensitivity is raised to well over 3σ even without using ND