Presentation on theme: "The Low-Energy Neutrino Factory Alan Bross, Malcolm Ellis, Steve Geer, Olga Mena, Silvia Pascoli “Olga and Silvia did all the clever stuff ” IPPP/06/85;"— Presentation transcript:
The Low-Energy Neutrino Factory Alan Bross, Malcolm Ellis, Steve Geer, Olga Mena, Silvia Pascoli “Olga and Silvia did all the clever stuff ” IPPP/06/85; DCPT/06/170; Roma-TH-1443; FERMILAB-PUB-07-021-E
Alan Bross IDS Meeting RAL January 16, 20082 Neutrino Factory – ISS Preliminary Design Proton Driver Target, Capture, Decay Bunching, Phase Rotation u Reduce E Cooling Acceleration 103 MeV 25 & 50 * GeV Storage/Decay ring * Still under study Why Study Low-Energy Neutrino Factory?
Alan Bross IDS Meeting RAL January 16, 20083 Well, Cost is Certainly a Motivation ISS Preliminary Going from 25 GeV (maybe 50) to 4 GeV u Eliminates FFAGs u Fewer RLAs u Smaller and possibly cheaper storage ring(s) u Saves 25-40% s $1B USD?
Alan Bross IDS Meeting RAL January 16, 20084 Up to now, the NFMCC has focused on neutrino factories with energies of 20-50 GeV The collaboration has not studied lower energy neutrino factories because, until recently, the proposed NF detectors have had muon energy thresholds (for measuring wrong-sign muons with adequate background rejection) of a few GeV, which imposes a minimum threshold on the desirable neutrino energy, and hence a minimum NF energy ~20 GeV. In the ISS there was progress on understanding how to reduce the detector thresholds for measuring wrong-sign muons … so we can now consider lower energy neutrino factories. But, Can the Physics Goals be Accomplished with a LE-NF?
Alan Bross IDS Meeting RAL January 16, 20085 Fine-Resolution Totally Active Segmented Detector Simulation of a Totally Active Scintillating Detector (TASD) using No a and Miner a concepts with Geant4 3 cm 1.5 cm 15 m u 3333 Modules (X and Y plane) u Each plane contains 1000 slabs u Total: 6.7M channels Momenta between 100 MeV/c to 15 GeV/c Magnetic field considered: 0.5 T Reconstructed position resolution ~ 4.5 mm 15 m 150 m B = 0.5T
Alan Bross IDS Meeting RAL January 16, 20086 “Special” Detector Has to be Magnetized Magnetized Totally Active Sampling Calorimeter 25kT Magnets 15m X 15m long -0.5T u Times 10! u Cost estimate s $140-680M –Conventional SC New Ideas u High T c SC s No Vacuum Insulation u VLHC SC transmission line s Technically proven s Might actually be affordable
Alan Bross IDS Meeting RAL January 16, 20087 Superconducting Transmission Line makes this concept possible (affordable) SCTL not a “concept” – prototyped, tested and costed for the VLHC Project at Fermilab
Alan Bross IDS Meeting RAL January 16, 20088 Parameters $1000/m $50M 100 kA op demonstrated
Alan Bross IDS Meeting RAL January 16, 20089 TASD Performance Event Reconstruction Efficiency Muon charge mis-ID rate Excellent E
Alan Bross IDS Meeting RAL January 16, 200810 E of TASD With the expected energy resolution of TASD it, can fully exploit the rich oscillation pattern at low energy 0.5 to 1.5 GeV (and go to E threshold of 0.5 GeV)
Alan Bross IDS Meeting RAL January 16, 200811 Detector Performance Issues What are the sensitivities to detector backgrounds? At low energy background rates grow substantially How does this affect the sensitivity of the analysis and the potential physics reach? and K decay in flight become the main background concerns u 1-5 X 10 -4 level. Figure of merit u Ratio of particle decay lengths to interaction lengths. s For TASD R= 1; for the Magnetized Fe-Scintillator detector it is 8. s So TASD 10 times worse than in Fe-Scint But, TASD will have vastly superior kink detection (40 hits on track before decay, continuous dE/dx meas. better E s We believe that these properties will allow us to control backgrounds to the 10 -3 level or better.
Alan Bross IDS Meeting RAL January 16, 200812 The Physics Study Baseline: 1480km (FNAL-Henderson) u Also did Homestake to Fermilab Choose NF Energy ~ 4 GeV (Actually 4.12 GeV). This is motivated by the realization that for baselines O(1000km), if 13 is not very small, the oscillation pattern is extremely rich below ~4 GeV. Will divide the simulated data into 3 energy bins, and fit the wrong-sign muon rates for each bin with positive- & negative- muons stored in the ring (6 rates to fit). Can also fit 6 right-sign muon rates. Energy bins: En = [0.8,1.5], [1.5,3.5], [3.5,4.12] GeV. Bins chosen to optimize ability to resolve degenerate solutions.
Alan Bross IDS Meeting RAL January 16, 200813 NF performance: BASIC: (5 years) (3 10 20 useful decays/yr) (2 signs) (20Kt fid. Mass) = 3 10 22 Kt-decays (2 signs) BETTER: (10 years) (5 10 20 useful decays/yr) (2 signs) (20Kt fid. Mass) = 1 10 23 Kt-decays (2 signs) Detector efficiency =0 for E n 0.5 GeV Energy resolution – 30% (extremely conservative: NOVA ~ 6%, expect TASD to be better) Central values chosen: sin 2 12 = 0.29, m 2 21 = 8x10 -5 eV 2, m 2 31 = 2.5x10 -3 eV 2 and 23 = 40°. Input Parameters
Alan Bross IDS Meeting RAL January 16, 200814 L=1480 Km Simulate 13 =3 o, =0 then fit e & e rates Fits for 3 neutrino energy bins: 13 (degrees) (degrees) Dark: 0.8 – 1.5 GeV Cyan: 1.5 – 3.5 GeV Magenta: >3.5 GeV Each fit yields one correct & one additional (“intrinsic degeneracy”) solution … but the additional solutions for the 3 bins do not overlap Unique Solution ! Illustration of how it works: 90%, 95%, 99% CL Contours Solutions corresponding to correct sign m 2 Resolving Degeneracies
Alan Bross IDS Meeting RAL January 16, 200815 13 (degrees) (degrees) Illustration of how it works: Repeat, analysis, picking the wrong sign for m 2. The solutions for the 3 bins are no longer consistent Can determine mass hierarchy. There is a 3 rd degeneracy, arising from the same predicted rates for 23 & /2- 23 … can show similar plots to illustrate how this degeneracy gets resolved. 90%, 95%, 99% CL Contours Solutions corresponding to incorrect sign m 2 Resolving Degeneracies II
Alan Bross IDS Meeting RAL January 16, 200816 Disappearance Channel Central values used: sin 2 23 = 0.4 and 0.44 Maximal mixing rejected at 99% CL if sin 2 23 < 0.48 ( 23 < 43.8°) in the low luminosity case 90%, 95% & 99% (2 dof) CL contours resulting from the fits at L = 1480 km, 3 x 10 22 kton-decays. Only disappearance data have been used
Alan Bross IDS Meeting RAL January 16, 200817 Golden Channel e 90%, 95% & 99% (2 dof) CL contours resulting from the fits at L = 1480 km, 1 x 10 23 kton-decays. 13 = 1°, four central values for = 0°, 90°, -90° & 180° No Background Background @ 10 -3
Alan Bross IDS Meeting RAL January 16, 200818 Mass hierarchy can be determined for all , if 13 > 3 o (sin 2 2 13 > 0.01) Mass Hierarchy L=1480 Km Hierarchy - 99% CL (2 D.O.F.) Red (no backgrounds) u Dotted - 1 X 10 23 KT- years u Solid – 3 X 10 22 KT-years Black (Background @ 10 -3 ) u Short dash - 1 X 10 23 KT- years u Long dash – 3 X 10 22 KT- years
Alan Bross IDS Meeting RAL January 16, 200819 Reach -CP Reach 99% CL (2D.O.F.) Red (no backgrounds) u Dotted - 1 X 10 23 KT- years u Solid – 3 X 10 22 KT-years Black (Background @ 10 -3 ) u Short dash - 1 X 10 23 KT-years u Long dash – 3 X 10 22 KT- years
Alan Bross IDS Meeting RAL January 16, 200820 95% CL Error on 13 vs. Bkg 13 = 2 o 13 = 3 o 13 = 8 o No dependence on for the several values of that have been studied
Alan Bross IDS Meeting RAL January 16, 200821 95% CL Error on Solid: = 0 Dashed: = 90 o 13 = 2 o 13 = 3 o 13 = 8 o
Alan Bross IDS Meeting RAL January 16, 200823 Summary A Low-Energy Neutrino Factory (coupled with the right detector) gives excellent capability to measure leptonic CP violation and explore the full neutrino mixing matrix, even if the mixing angle 13 is very small ( 13 ~ 1°). In the absence of backgrounds, the neutrino mass hierarchy could be resolved down to sin 2 2 13 =0.002 (0.0003) in the low (high) luminosity scenario, regardless of the value of the CP violating phase . If we add a 10 -3 background, those limits translate into 0.005 and 0.001. The 99% CL (2 dof) error on the CP violating phase is 0.01 (0.001) in the most pessimistic (optimistic) scenario.
Alan Bross IDS Meeting RAL January 16, 200824 Summary The intrinsic degeneracy is resolved due to the energy binning analysis at the 99% CL. The 23 degeneracy is also solved in the range 2° < 13 < large as well as from 13 = 2° down to 13 = 0.5 ° in both the low and high luminosity scenarios due to the impact of the solar term at small energies and large distances. For the intermediate values 13 ~ 2°, the 23 degeneracy is present only at the 95, 99% CL (2 dof) in the low luminosity scenario, but it does not interfere with the measurement of CP violation. Maximal mixing is rejected at the 99% CL (2dof) if 23 > 43.8° just-by exploiting the disappearance data. Even if 13 -> 0, from the disappearance channel data, we could determine the neutrino mass hierarchy at the 95% CL (2 dof) in the high luminosity scenario.
Alan Bross IDS Meeting RAL January 16, 200825 Outlook A Low-Energy Neutrino Factory (coupled with the right detector) gives excellent capability in exploring the full neutrino mixing matrix and measure leptonic CP violation A finely segmented TASD is quite possibly the right analysis tool for a Low-Energy NF u Much more simulation/study needs to be done, but the initial results are promising A Low-Energy Neutrino Factory (4 GeV) is certainly cheaper than a 20-50 GeV facility ( -25-40%) Plus with proper planning a Low-Energy Neutrino Factory might be upgradeable to higher energy
Alan Bross IDS Meeting RAL January 16, 200826 Target, B-rot, Cool Mu2e 8GeV 4GeV NuFact MC-R&D Hall 0.2-4GeV mu-Linac To DUSEL Low Energy NF and Project X