21 march 2007 LAUNCH Heidelberg Alain Blondel SYSTEMATIC ERRORS for accelerator-based long baseline experiments -- cross-sections -- matter effects From HARP/K2K/T2K… to Neutrino Factory

21 march 2007 LAUNCH Heidelberg Alain Blondel Mid-energy region: QE+ 1  + n  Super beam (Numi off, T2KK, CNGS+) high Energy beta-beam (CERN highQ or SPS+) WATER CHERENKOV (Mton) TASD (NOvA), Larg TPC Low energy region: QE dominates Low energy super beam (T2K, T2HK, T2KK, Frejus) Low energy beta-beam (CERN baseline scenario) WATER CHERENKOV (Mton) High-energy region: DIS Neutrino Factory Magnetized Iron Emulsion large magnet around: emulsion, TASD, Larg

21 march 2007 LAUNCH Heidelberg Alain Blondel JPARC- ~0.6GeV beam 0.75 MW 50 GeV PS (2009  ) Kamioka J-PARC SK: 22.5 kt Phase II: 4 MW upgrade Phase II HK: 1000 kt K2K ~1.2 GeV beam 0.01 MW 12 GeV PS (1999  2005) (1999  2005) K2K & T2K

21 march 2007 LAUNCH Heidelberg Alain Blondel K2K ran GeV protons WBB flux X cross-sections poorly known from first principles measured in near detectors: Most useful turned out to be -- scibar (water + scint) -- MRD

21 march 2007 LAUNCH Heidelberg Alain Blondel    event Sci Fi

21 march 2007 LAUNCH Heidelberg Alain Blondel Far flux different from near flux (solid angle) neutrino cross-sections poorly known at low energies near detector is also a cross-section measurement device, PROVIDED FLUX IS KNOWN ==> hadron production measurements far/near ratio

21 march 2007 LAUNCH Heidelberg Alain Blondel Hadron production on nuclear targets is a) complicated b) uninteresting for hadronic physics c) difficult to measure well d) absolutely mandatory for neutrino beam experiments ==> data are sparse and Monte-Carlos are very uncertain measure! GeV/c, H2  Pb incl Al 12.9 GeV/c, (K2K) Be 8.9 GeV/c (MiniBooNE)

21 march 2007 LAUNCH Heidelberg Alain Blondel HARP approved 2000 built in 17 months run sept > nov triggers at each of these settings Beam line PID Forward detectors --> neutrino beams - K2K, - Miniboone, - atmospheric, - Low energy SPL superbeam Large Angle detectors -->neutrino factory

21 march 2007 LAUNCH Heidelberg Alain Blondel

MINIBOONE!!!!! hep-ex/

21 march 2007 LAUNCH Heidelberg Alain Blondel Figure 9 Muon neutrino fluxes in the K2K experiment as a function of neutrino energy E, as predicted by the default hadronic model in the K2K beam Monte Carlo simulation (dotted histograms),and by the HARP  + production measurement (filled circles with error bars). Left: unit-area normalized flux predictions at the K2K near (top) and far (bottom) detector locations,  near and  far ; right : the far – to – near flux ratio (empty squares with error boxes show the K2K model results), showing the precision improvement brought by the HARP data.

21 march 2007 LAUNCH Heidelberg Alain Blondel no oscillation flux*0.6 best osc. fit reconstructed « single ring » Quasi-elastics in SuperKamiokande ==> spectral shape + normalization show oscillation K2K final results (using HARP input + near detectors 4.1 -> 4.4  C.L. improved by factor 3) arXiv:hep-ex/ v2 sept 06

21 march 2007 LAUNCH Heidelberg Alain Blondel CC Quasi-elastic From PCAC The axial form-factor; the standard dipole form M A is a free parameter (the only one) and it is obtained from experiments. Limited by systematic errors… it is a tough measurement!. CVC – use electron scattering data for the dipole and form factors.

21 march 2007 LAUNCH Heidelberg Alain Blondel MA= Measurement of Quasi Elastic events in the SciFi near detector

21 march 2007 LAUNCH Heidelberg Alain Blondel CC Quasi-elastic Knowledge of CC-QE cross- section is poor. It is also not covering the threshold. This could be important for low energy neutrino experiments. Note the different threshold for Electron, muon …and tau neutrinos

21 march 2007 LAUNCH Heidelberg Alain Blondel 3 CC channels for neutrino reactions: Dominant contribution s comes from: CC-1  They can be related by isospin relations except for nuclear corrections. Theory is built as a mixture of electron data, free parameter and theory as in CCQE.

21 march 2007 LAUNCH Heidelberg Alain Blondel The overall cross sections for CC1  (with the W ≤ 2 GeV cut): CC-1  It is not well measured and it depends on the W cut (higher mass resonances –up to 18- and non-resonant region)

21 march 2007 LAUNCH Heidelberg Alain Blondel Very little is known about NC pion production: (NC π 0 and  +- production are important backgrounds!) NC-1 

21 march 2007 LAUNCH Heidelberg Alain Blondel CC-1  and NC-1  in T2K 50% of background in e appearance is due to NC-1  0

21 march 2007 LAUNCH Heidelberg Alain Blondel    Single ring events in super KamiokaNDE    Nuclear reinteractions

21 march 2007 LAUNCH Heidelberg Alain Blondel T2K neutrino experiment at JPARC Approved since 2003, first beam in April Priorities : 1. search for, and measurement of,   e appearance  sin 2 2  precise measurement of    disappearance  sin 2 2  23 and  m (Longer term) precise measurement of   e,   e Matter effects and CP violation

21 march 2007 LAUNCH Heidelberg Alain Blondel T2K Physics Goals 2 Measurement of  m 2 23 with accuracy of 3% mixing angle with accuracy of 1%  (sin 2 2  23 )  0.01  (  m 2 23 ) < 1  eV 2 3 Search for sterile components by NC events 1 Search for     e appearance sensitivity sin 2 2  13  0.01

21 march 2007 LAUNCH Heidelberg Alain Blondel T2K Scheme: Neutrino oscillations: measured neutrino events in SK prediction without oscillations (flux.  ) -- the near detector neutrino flux is not identical to far detector neutrino flux (geometry)  resulting uncertainties in the near/far ratio are thus not well known (up to 20%) -- there is no absolute secondary hadron flux measurement available on the T2K beam line  cross-sections cannot be measured -- there exist no measurement of particle production off carbon with 30 GeV protons 30 (->50) GeV protons on 90 cm carbon target   (disappearance) CC  near/far ratio is *not* flat  ,K,K p 110 m

21 march 2007 LAUNCH Heidelberg Alain Blondel near/far ratio for backgrounds (esp. e ) are not constant either plots from Max Fechner’s thesis CC  e  e flux important for   e appearance search: signal cross-section, backgrounds requires measurement of      

21 march 2007 LAUNCH Heidelberg Alain Blondel Near Detectors at 280 m Off-axis (~2 o ) On-axis (0 o )  19m Super-K Beam center 37m ND280m hall Accuracy of beam direction 0.18 mrad

21 march 2007 LAUNCH Heidelberg Alain Blondel NA-49 Set-up beam TPC ToF NA49-future: Study of hadron production in collisions of protons and nuclei at the CERN SPS Run in 2007 has been approved

21 march 2007 LAUNCH Heidelberg Alain Blondel Improvement that the NA49 data could bring to the T2K results on atmospheric oscillation parameters: 90%CL   2 = 4.7

21 march 2007 LAUNCH Heidelberg Alain Blondel 300 MeV  Neutrinos small contamination from e (no K at 2 GeV!) A large underground water Cherenkov (400 kton) UNO/HyperK or/and a large L.Arg detector. also : proton decay search, supernovae events solar and atmospheric neutrinos. Performance similar to J-PARC II There is a window of opportunity for digging the cavern stating in 2009 (safety tunnel in Frejus) CERN-SPL-based Neutrino SUPERBEAM Fréjus underground lab. target!

21 march 2007 LAUNCH Heidelberg Alain Blondel CERN:  -beam baseline scenario PS Decay Ring ISOL target & Ion source SPL Cyclotrons, linac or FFAG Decay ring B = 5 T L ss = 2500 m SPS ECR Rapid cycling synchrotron Nuclear Physics Same detectors as Superbeam ! Also: 8 Li and 8 B  8 Be (larger Q) target! Stacking! neutrinos of E max =~600MeV

21 march 2007 LAUNCH Heidelberg Alain Blondel -- Neutrino Factory -- CERN layout --    e + e   _ interacts giving   oscillates e     interacts giving    WRONG SIGN MUON Golden Channel p/ s  s =  yr e  yr   yr  yr target! cooling! acceleration! also (unique) e      Silver channel

21 march 2007 LAUNCH Heidelberg Alain Blondel 1.Both (BB+SB+MD) and NUFACT outperform e.g. T2HK on most cases. 2. combination of BB+SB is really powerful. 3. for sin 2 2   below 0.01 NUFACT as such outperforms anyone 4. for large values of   systematic errors dominate. Matter effects for NUFACT, cross-sections for low energy beams. This is because we are at first maximum or above,  CP asymmetry is small! matter effect for NUFACT

21 march 2007 LAUNCH Heidelberg Alain Blondel for NUFACT:  work on systematic errors on matter effect A preliminary study was made by E. Kozlovskaya, J. Peltoniemi, J. Sarkamo, The density distribution in the Earth along the CERN-Pyhäsalmi baseline and its effect on neutrino oscillations. CUPP-07/2003  the uncertainties on matter effects are at the level of a few% J. Peltoniemi

21 march 2007 LAUNCH Heidelberg Alain Blondel

Errors in density location length“a priori”“best” Continental 2500 km4.7%2.9% Oceanic 2500 km2.6%1.7% Continental 9000 km2.0%1.7% Oceanic 9000 km1.8%1.5% Errors are ~2 sigma (but not really Gaussian) Avoid perturbed terrain (europe or US to Japan, across the alps, etc…) Dedicated study would reduce errors to below 2%  2% is standard hypothesis for Nufact studies

21 march 2007 LAUNCH Heidelberg Alain Blondel near detector constraints for CP violation = A CP  sin 2    solar term… sin  sin (  m 2 12 L/4E) sin   sin   P( e   ) - P( e   ) P( e   ) + P( e   ) Near detector gives e diff. cross-section*detection-eff *flux and ibid for bkg BUT: need to know  and  diff. cross-section* detection-eff with small (relative) systematic errors.  knowledge of cross-sections (relative to each-other) required  knowledge of flux! interchange role of e and  for superbeam ex. beta-beam or nufact:

21 march 2007 LAUNCH Heidelberg Alain Blondel need to know this: experimental signal= signal cross-section X efficiency of selection + Background and of course the fluxes… but the product flux*  sig is measured in the near detector this is not a totally trivial quantity as there is somethig particular in each of these cross-sections: for instance the effects of muon mass as well as nuclear effects are different for neutrinos and anti-neutrinos while e.g. pion threshold is different for muon and electron neutrinos

21 march 2007 LAUNCH Heidelberg Alain Blondel 3.5 GeV SPL  beam -- low proton energy: no Kaons  e background is low --region below pion threshold (low bkg from pions) but: low event rate and uncertainties on cross-sections

21 march 2007 LAUNCH Heidelberg Alain Blondel Uncertainties in the double ratio (Sobczyk at RAL meeting) 1. problem comes from compound of Fermi motion and binding energy with the muon mass effect. the double ratio calculation is very insensitive to variations of parameters … but

21 march 2007 LAUNCH Heidelberg Alain Blondel at 250 MeV (first maximum in Frejus expt) prediction varies from 0.88 to 0.94 according to nuclear model used. Hope to improve results with e.g. monochromatic k-capture beam Sobzyk

21 march 2007 LAUNCH Heidelberg Alain Blondel FLUX in NUFACT will be known to see CERN YELLOW REPORT this was studied including -- principle design of polarimeter, and absolute energy calibration -- principle design of angular divergence measurement -- radiative corrections to muon decay -- absolute x-section calibration using neutrino – electron interactions (event number etc… considered) this is true for Polarization (t) Fourier transform  dN(E)/dE

21 march 2007 LAUNCH Heidelberg Alain Blondel Neutrino fluxes  + -> e + e    e ratio reversed by switching      e spectra are different No high energy tail. Very well known flux (10 -3 ) - absolute flux measured from muon current or by  e - ->    e in near expt. -- in triangle ring, muon polarization precesses and averages out (preferred, -> calib of energy, energy spread) -- E&s E calibration from muon spin precession -- angular divergence: small effect if  < 0.2/ , can be monitored  polarization controls e flux:  + -X> e in forward direction

21 march 2007 LAUNCH Heidelberg Alain Blondel storage ring shielding the leptonic detector the charm and DIS detector from the precision of this sketch, it can be concluded that a lot remains to be done. for instance: is shielding necessary at all? Polarimeter Cherenkov

21 march 2007 LAUNCH Heidelberg Alain Blondel CONCLUSIONS Total and differential cross – section measurements will take place in the near detectors as a necessary by-product of the long baseline neutrino experiments. There are a number of such projects covering the lower energy part of the spectrum: -- T2K (E= MeV) ND280 and perhaps 2km -- MINERvA (E=1.5-3 GeV) In each case the knowledge of the flux requires hadroproduction experiments. HARP achieved a global precision of 5-8% (short of the aim of 1%!). MIPP at FNAL and NA49-future CERN will try to do the same at GeV and 5-85 GeV respectively These experiments are more difficult than one naively expects, partly because they donc provide fundamental physics results of their own. A global precision of +- 5% may be expected On longer time scale beta-beam and neutrino factory (Storage decay ring facilities) will allow flux control to a fraction of a percent. Control of cross-sections will become possible at one order of magnitude better than now. Matter effects can me mastered with a precision of about +- 2% but require dedicated study in collaboration with geophysicists.

21 march 2007 LAUNCH Heidelberg Alain Blondel Systematic uncertainties due to the hadron production model F/N ratio difference among hadron production models: ~ E 1GeV Syst. error due to F/N Goal of T2K  Impossible to achieve T2K GOAL! It is difficult to evaluate the validity of the hadron production model !!  The uncertainty is probably not less than the difference among several models inspired by similar data sets   momentum   flux G-FLUKA vs. MARS vs. FLUKA up to ~20% difference! e appearance  disappearance e appearance  disappearance Ratios of F/N ratios  (sin 2 2  23 )~  0.01,  (  m 23 2 )<~  3 10  5 eV 2  (sin 2 2  23 )~  ,  (  m 23 2 )<~   5 eV 2 MARS/G-FLUKA FLUKA/G-FLUKA

21 march 2007 LAUNCH Heidelberg Alain Blondel T2K with and without NA49: I.  13 discovery: GOAL: search down to sin 2  13 ~0.008 (90%CL) (signal ~ 10 / 20 bkg, ~20% stat. error) NC  0 and CC e backgrounds will be predicted from the near detector Achieving the above goal requires  (N/F) (all sources of errors) < 10% ==> requirement on  (N/F) from hadro-production: <2-3% This can be achieved in NA49 with 10% precision on pion rates and K 0 / , K  /  ratio. NA49 has achieved 3% on both in the past. present status: -- no 30 GeV p-Carbon data -- interpolation between 12 GeV p-C (HARP, no K yet, no K 0 ) and 158 GeV (NA49!) required -- anomalous behaviour of K/pi ratio (3 to 7%) observed in nearby nuclei ==> errors on hadro-production are at least % level and uncertain Without NA49, uncertainties in the particle production would yield the largest error on the background estimate to   e search and preclude to achieve the aspired systematics. The T2K experiment is still limited by statistics and sensitivity would be worsened by ~10-20%. This is as much an issue of reliability than of precision.

21 march 2007 LAUNCH Heidelberg Alain Blondel T2K with and without NA49: II. Atmospheric oscillation parameters sin 2 2  23,  m 2 23 Statistical accuracy:  sin 2 2  23 ~0.01,  (  m 2 23 ) = eV 2 (1%) statistics nonQE/QE (20%) Energy scale (4%) 10% on flux 10% on flux width flux slope (20%) In the presently favored region of  m 2 23 the flux related errors are important wrt statistical accuracy. The 20-30% uncertainties on particle production would lead to up-to-20% errors on N/F ratio and would spoil the measurements, with syst. errors as large as  sin 2 2  23 ~ ,  (  m 2 23 ) = eV 2 An NA49 measured precision of 10% per bin would lead to a N/F ratio error of 2-3% and render these small. Without NA49-T2K, ill-defined flux-errors would be worse than the statistical precision, and spoil the atmospheric parameters measts

21 march 2007 LAUNCH Heidelberg Alain Blondel INO ~7000 km (Magic distance)

21 march 2007 LAUNCH Heidelberg Alain Blondel A revealing comparison: A detailed comparison of the capability of observing CP violation was performed by P. Huber (+M. Mezzetto and AB) on the following grounds -- GLOBES was used. -- T2HK from LOI: 1000kt, 4MW beam power, 6 years anti-neutrinos, 2 years neutrinos. systematic errors on background and signal: 5%. -- The beta-beam He dk/year Ne dk/year (5 +5yrs) The Superbeam from 3.5 GeV SPL and 4 MW. Same 500kton detector Systematic errors on signal efficiency (or cross-sections) and bkgs are 2% or 5%. --NUFACT  + and  + per year for 10 years 100 kton iron-scintillator at 3000km and 30 kton at 7000km (e.g. INO). (old type!) The matter density errors of the two baselines (uncorrelated): 2 to 5% The systematics are 0.1% on the signal and 20% on the background, uncorrelated. all correlations, ambiguities, etc… taken into account

21 march 2007 LAUNCH Heidelberg Alain Blondel  [ ]  [ ]

21 march 2007 LAUNCH Heidelberg Alain Blondel  [ ]  [ ] NB: 3sigma = 6 0 means that +-1 sigma =