In this talk I compare the physics potential of possible future neutrino
oscillation experiments from CERN to a Mt scale water Cerenkov detector at
Frejus (MEMPHYS) and of the T2HK proposal in Japan, where for the CERN
experiments an SPL Superbeam and a $\gamma=100$ Beta Beam are considered.Comment: Talk given at NOW 2006, 9-16 Sep 2006, Conca Specchiulla, Otranto,
  Italy, 3 pages, 2 figure

Autin

Barger

Benedikt

Bouchez

Campagne

Casper

de Bellefon

Huber

Itow

Kobayashi

Mezzetto

Nakamura

NUANCE event generator (v3)

Thomas Schwetz

English

arXiv

Crossref

Comparison of the CERN–MEMPHYS and T2HK neutrino oscillation experiments

In this talk I compare the physics potential of possible future neutrino oscillation experiments from CERN to a Mt scale water Cerenkov detector at Frejus (MEMPHYS) and of the T2HK proposal in Japan, where for the CERN experiments an SPL Superbeam and a $\gamma=100$ Beta Beam are considered.In this talk I compare the physics potential of possible future neutrino oscillation experiments from CERN to a Mt scale water Cerenkov detector at Frejus (MEMPHYS) and of the T2HK proposal in Japan, where for the CERN experiments an SPL Superbeam and a $\gamma=100$ Beta Beam are considered

Schwetz, Thomas

CERN Document Server

arXiv:hep-ph/0611261 v1   20 Nov 2006 CERN-PH-TH/2006-241Comparison of the CERN–MEMPHYS and T2HK neutrino oscillationexperiments∗Thomas SchwetzaaCERN, Physics Department,Theory Division, CH-1211 Geneva 23, SwitzerlandIn this talk I compare the physics potential of possible future neutrino oscillation experiments from CERN toa Mt scale water Cˇerenkov detector at Fre´jus (MEMPHYS) and of the T2HK proposal in Japan, where for theCERN experiments an SPL Superbeam and a γ = 100 Beta Beam are considered.1. INTRODUCTIONNeutrino oscillation physics is now entering theera of precision experiments [1]. The main aimof the upcoming generation of experiments willbe to establish a non-zero value of the mixingangle θ13 or to push further the bound. On atime scale of 5 to 10 years decisions on a subse-quent generation of high precision neutrino oscil-lation facilities will have to been taken, and cur-rently active investigations on comparing variousoptions are performed [2]. Along these lines, inthis talk I consider three particular setups whichare comparable in size and time scale, namelytwo CERN based neutrino oscillation experimentsconsisting of a Beta Beam (βB) [3] with γ = 100and a Superbeam (SPL) [4], as well as the phaseII of the T2K experiment in Japan (T2HK) [5].All three configurations use a Mt scale waterCˇerenkov detector [6]: MEMPHYS [7] at Fre´jusor the Hyper-Kamiokande [8] detector in Japan.The main characteristics of the setups are dis-played in Tab. 1. The results presented here arebased on the work [9], where details on the calcu-lations, references, and more physics results anddiscussions can be found.2. SENSITIVITY TO θ13 and CPVAs performance indicators for the consideredexperiments we use the potential to establish anon-zero value of θ13 and the sensitivity to CP∗Talk given at NOW 2006, 9–16 Sep 2006, Conca Spec-chiulla, Otranto, ItalyβB SPL T2HKDet. mass 440 kt 440 kt 440 ktBaseline 130 km 130 km 295 km〈Eν〉 [MeV] 400 300 760Time (ν/ν¯) 5/5 yr 2/8 yr 2/8 yrBeam 5.8 (2.2) · 1018 4 MW 4 MWSystematics 2–5% 2–5% 2–5%Table 1Summary of default parameters used for thesimulation of the βB, SPL, and T2HK experi-ments. For the βB the beam intensity is givenin 6He(18Ne) decays/yr.violation (CPV). The θ13 sensitivity is shown inFig. 1 (left) as a function of the value of the CPphase δCP: above the curves θ13 = 0 can be ex-cluded at more than 3σ CL (i.e., with ∆χ2 ≥ 9),whereas Fig. 1 (right) shows the region in theθ13 − δCP plane where CPV can be established at3σ.One finds from these plots that SPL and T2HKperform rather similar. In fact, the experimen-tal setups of these two configurations are similar(Superbeam technology, multi-MW beam power,detector, L/Eν), the main differences being theshorter baseline of SPL which implies lower neu-trino energies (compare Tab. 1), as well as theuse of an on-axis (off-axis) configuration for SPL(T2HK). The lower energies for SPL imply thatthe cross section is completely dominated byquasi-elastic (QE) scattering which allows a goodreconstruction of the neutrino energy, whereas at120 pi/2 pi 3pi/2 2pitrue δCP10-410-310-2sin2 2θ 13Sensitivity to a non-zero θ13 at 3σβBT2HKSPL10-4 10-3 10-2 10-1true  sin22θ130pi/2pi3pi/22pitrue  δCPT2HKSPLβB Sensitivity to CP violation at 3σσsyst = 2%−5%∆χ2 (δCP = 0, pi) = 9Figure 1. Left: 3σ sensitivity to sin2 2θ13 for βB, SPL, and T2HK as a function of δCP. Right: CPVdiscovery potential for βB, SPL, and T2HK: for parameter values inside the ellipse-shaped curves CPconserving values of δCP can be excluded at 3σ (∆χ2 > 9). The width of the bands corresponds to valuesfor the systematical errors between 2% and 5%. The dashed curves show the sensitivity of the βB whenthe number of ion decays/yr are reduced by a factor of two with respect to the values given in Tab. 1.T2HK energies non-QE events contribute signif-icantly. On the other hand in the low energyregime Fermi motion becomes important whichlimits energy reconstruction. In our analysis wehave taken these issues into account by a mi-gration matrix between true and reconstructedneutrino energies based on detailed event simula-tions [9].Within our standard setup the βB performsclearly better than the Superbeams. For theβB a crucial parameter is the total number ofion decays. The conservative numbers from theEURISOL βB studies [10], which are two timessmaler than our standard values, lead to the sen-sitivites shown as dashed curves in Fig. 1.The widths of the curves in the figures showsthe effect of varying the (uncorrelated) system-atical uncertainties on signal and backgroundsbetween 2% and 5%. One can see that theβB is practically unaffected, whereas the Super-beam performances, and in particular the one ofT2HK, depend to some extent on the systemat-ics. The relevant systematic in this respect isthe uncertainty on the background. In the βBthe most important background comes from pionsproduced mainly in NC νe/ν¯e interactions whichare misidentified as muons. This background isefficiently reduced by requiring to see the Michelelectron from the muon decay. After applying allthe cuts roughly 300 background events remain.The reason why an uncertainty on this numberhas so little impact for the βB is that the back-ground has a very different shape than the signal.As visible in Fig. 2 it is peaked at low energies andtherefore spectral information makes the βB veryinsensitive to the systematical uncertainty.In contrast, for the Superbeams the back-ground comes mainly from the intrinsic νe/ν¯ecomponent of the beam and has a spectral shaperather similar to the signal, as illustrated in Fig. 2for the SPL. Therefore spectral information is notas efficient to distinguish the background from thesignal, as in the case of the βB.3. COMMENTS ON DEGENERACIESIn analyses of long-baseline experiments pa-rameter degeneracies play an important role.3050100150200events per bin0 0.2 0.4 0.6 0.8 1reconstructed Eν  [GeV]050100150200events per bin0 0.2 0.4 0.6 0.8 1reconstructed Eν  [GeV]Event spectra   (sin22θ13 = 0.01,  δCP = 0)βB (neutrinos)SPL (anti-neutrinos)SPL (neutrinos)βB (anti-neutrinos)signals backgroundFigure 2. Signal and background energy spectrafor SPL (top) and βB (bottom).There are three types of degeneracies [11], tra-ditionally referred to as intrinsic-, octant-, andsign(∆m231)-degeneracy. For the experiments dis-cussed here the intrinsic degeneracy is resolved byspectral information but the degeneracies relatedto the octant of θ23 and the neutrino mass hier-archy are present and lead to ambiguities in thedetermination of θ13 and δCP. However, thanksto the fact that the matter effect is rather small(due to the relatively short baselines) the degen-eracies have very little impact on the sensitivityto CPV. In other words, if the true parametervalues are CP violating also the parameter valuesof the degenerate solutions will be CP violating.Moreover, as shown in Ref. [12] atmosphericneutrino data in Mt scale water Cˇerenkov de-tectors as considered here can be used to re-solve degeneracies (see also Ref. [9]). By combin-ing long-baseline and atmospheric data the masshierarchy can be identified at 2σ CL providedsin2 2θ13 & 0.02− 0.03, although none of the con-sidered experiments has sensitivity to the hierar-chy from long-baseline data alone. Furthermore,atmospheric data provides sensitivity to the oc-tant of θ23, and if combined with the νµ disap-pearance chanel available in the Superbeam ex-periments there is sensitivity to the octant for| sin2 θ23 − 0.5| & 0.05.ACKNOWLEDGEMENTSI thank J.-E. Campagne, M. Maltoni, andM. Mezzetto for collaboration on this topic.These results have been obtained using theGLOBES [13] and NUANCE [14] software pack-ages. The work of T.S. has been supported by the6th Framework Program of the European Com-munity under a Marie Curie Intra-European Fel-lowship at SISSA, Trieste, Italy.REFERENCES1. Contributions of M. Bonesini, A. Cabrera,Y. Declais, P. Huber, T. Kajita, I. Kato,S. Kopp, M. Lindner, B. Rebel, these pro-ceedings.2. See, e.g., International Scoping Studyhttp://www.hep.ph.ic.ac.uk/iss/3. M. Mezzetto, J. Phys. G 29 (2003) 1771;J. Bouchez, M. Lindroos, M. Mezzetto, AIPConf. Proc. 721 (2004) 37.4. J. E. Campagne and A. Cazes, Eur. Phys. J.C 45 (2006) 643; M. Baylac et al., Conceptualdesign of the SPL II, CERN-2006-006.5. Y. Itow et al., hep-ex/0106019; T. Kobayashi,Nucl. Phys. Proc. Suppl. 143 (2005) 303.6. S. Katsanevas, these proceedings.7. A. de Bellefon et al., hep-ex/0607026.8. K. Nakamura, Int. J. Mod. Phys. A 18 (2003)4053.9. J. E. Campagne, M. Maltoni, M. Mezzettoand T. Schwetz, hep-ph/0603172.10. B. Autin et al., J. Phys. G 29, 1785 (2003);M. Benedikt, A. Fabich, S. Hancock andM. Lindroos, Nucl. Phys. Proc. Suppl. 155(2006) 211.11. V. Barger, D. Marfatia and K. Whisnant,Phys. Rev. D 65, 073023 (2002).12. P. Huber, M. Maltoni and T. Schwetz, Phys.Rev. D 71 (2005) 053006 [hep-ph/0501037].13. P. Huber, M. Lindner and W. Winter,Comput. Phys. Commun. 167 (2005) 195,http://www.ph.tum.de/~globes14. NUANCE event generator (v3),http://nuint.ps.uci.edu/nuance/,D. Casper, Nucl. Phys. Proc. Suppl. 112(2002) 161.

Comparison of the CERN-MEMPHYS and T2HK neutrino oscillation experiments

Comparison of the CERN-MEMPHYS and T2HK neutrino oscillation experiments

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