A long-baseline experiment with the IHEP neutrino beam Y. Efremenko detector Presented by

Prospects to measure neutrino oscillation pattern with very large area underground detector at very long baselines V. Ammosov, V. Garkusha, A. Ivanilov, V. Kabachenko, E. Melnikov, F. Novoskoltsev, A. Soldatov, A. Zaitsev IHEP, Protvino, Russia hep-ph/

5.1 km Concept Measurement of  disappearance with a very large baseline UNK tunnel - huge scintillator based muon counter (not calorimeter !) Surrounding soil is a neutrino target TOF and segmentation gives direction to the neutrino source Location at 50 m underground gives good cosmic ray background suppression Energy scan with Narrow Band neutrino beam to see oscillation pattern UNK tunnel (Left from terminated accelerator project at the IHEP, Protvino, Russia)

Location ~7600 km ~7000 km ~2000 km

Range for oscillation This set of L/E will let us to: Observe the oscillation pattern Give as precise measurement of  m 2 and mixing Measure asymmetry in P(  ) v.s. P(anti-  ) due to matter effect   and  13 measurement test CPT violation For beam energy 1-15 GeV GSI, and JHF (or FNAL) are in right place to cover at least one full oscillation wave

Concept of neutrino beam Needed energy resolution Blue line – mono energeticGreen line -  E /E =15% Red line-  E / E =40%  E / E =15% (Narrow band beam) is adequate to see full oscillation wave

2 graphite target H1,H2 - 3 m parabolic horns ( 200 kA ) B1,B2 - 2 m dipoles with 400 mm gap 400 m decay region ( 40 m target area)  2 m decay pipe Energy setting is tuned by scaling dipole current and adjustment of target location Neutrino focusing system

Proton energy 50 GeV Beam Simulations 1.7, 3.5, 7.0, 10.5 and 14.0 GeV energy settings  CC events -solid lines anti-  CC events - dashed lines M

Concept of the Detector Extruded polystyrene sc. plates (production in IHEP) PMMA Kumarin-30 doped WL shifters light collection from both ends via PMTs or APD 10 ph. el. per MIP TDC and ADC for each readout channel Not all parts of the tunnel is equally efficient. Some optimization is possible

Detector Acceptance (MC study) Conclusions: background from NC as well as from ν τ and ν e is at a level of a few % Ratio of an acceptances for neutrino and antineutrino does not depends of the energy Selection criteria: Two hits in different scintillator modules Time difference between hits is greater than 10 ns (tunnel diameter 5 m.) Angle between neutrino and "track" directions is less than 30 0 Only up going tracks

Expected Statistics Let consider How many POT we need to detect 1000  CC events (no oscillation) for the following beam settings ~10 21 Protons on Target is enough !!! Mixing Realistic NB beam

Background SourceValue for 10 7 s Cosmic  within accepted solid angle 0.8 (  > 92 0 ) Secondaries from cosmic muon interactions ~40 from MACRO data  from wrong TOF ID 0.2 (6  of TOF ) Cosmic background < 50 events/year Caveat: tunnel radioactivity have to be measured If we can deliver POT during 10 7 sec, with fact extraction, Effective Detector life time could be ~ 1-10sec!

For  m atm 2 in the range of ev 2 <  m 2 < ev 2 Expected accuracy in parameters measurements For GSI:   m 2 = 2.7  ev 2,  Sin 2 2  = 0.01 For JHF:   m 2 = 1.5  ev 2,  Sin 2 2  = 0.01 This is ~1% error !!! If we can do the same for antineutrinos say with 2% accuracy, then: Test of CTP on the 3% level by compare  m 2 for neutrinos with  m 2 for antineutrinos Sensitivity to matter effects on the 3% level For  = P(  ) -- P(anti-  ) Expected Sensitivity

Terrestrial Matter Effects |  m 32 2 | = 2.5·10 -3 eV 2  23 = 40 o  13 = 13 o (s 13 2 = 0.05)  m 21 2 = 1.4·10 -4 eV 2  12 = 35 o Calculations correspond to: Conclusions: Beam spread  E/E = 0.15 is sufficient. There are “significant” terrestrial effects For 7000 km baseline matter effects become dramatic! GSI JHF vacuum, no smearing Vacuum, smearing  E/E = 0.15 matter  matter anti- 

TME: asymmetry A CPT Black:  m 32 2 > 0 Blue:  m 32 2 < 0 Solid:  = 0 o Dashed:  = 180 o GSI JHF Conclusions: determination of the sign of  m 32 2 by the sign of asymmetry A CPT is possible Some information of the CP phase could be obtained as well

Conclusion Observation of oscillation patterns for  and anti-  disappearance in the range 0.5·10 -3 <  m 2 < 6.0·10 -3 eV 2 Measurement of  m 2 and I  with accuracy of ~ 1% Search for genuine CPT violation in neutrino sector with accuracy of ~ 3% for the  =  m 2 (  )-  m 2 (anti-  ) Observation of the matter effects Unambiguous determination of the sign of  m 32 2 by the sign of asymmetry A CPT For the very long baseline, narrow band beam, coarse Mt size detector, and ~10 21 POT it is possible to:

Phase vs. Theta 13 TME:  vs. s 13 2 measurement: at E = 1 GeV in dependence on  and s 13 2 for  m 21 2 = 1.4·10 -4 and 2.7· eV 2 eV 2 One point corresponds to s 13 2 = 0 (black circle) and five points with  = 0 o, 45 o, 90 o, 135 o and 180 o (marked by the same symbols) are plotted for the values of s 13 2 = 0.01 (boxes), 0.03 (circles) and 0.05 (diamonds). Straight line grid presents A CPT = 0 (blue line),  0.04,  0.08, … (brown lines). Errors are for point (s 13 2 = 0.03,  = 45 o ) and correspond to statistics of 10 3 events in the absence of oscillations. Conclusion:  and s 13 2 can be measured with the use of A CPT (terrestrial effect)