STATUS OF BNL SUPER NEUTRINO BEAM PRORAM W. T. Weng Brookhaven National Laboratory NBI2003, KEK November 7-11, 2003
OUTLINE Physics Reach from a Very Long Baseline Neutrino Beam AGS High Intensity Performance AGS Upgrade (1MW): AGS Upgrade (4MW) Chronology of BNL Super Neutrino Beam Program Conclusion
Physics Goals of the Very Long Baseline Neutrino Program We introduce a plan to provide the following goals in a single facility : • precise determination of the oscillation parameters ∆ m 32 2 and sin 2 2 θ 23 • detection of the oscillation of ν µ → ν e and measurement of sin 2 2 θ 13 2 sin 2 2 θ 12 in a ν µ → ν e appearance mode, • measurement of ∆ m 21 independent of the value of θ 13 • verification of matter enhancement and the sign of ∆ m 32 2 • determination of the CP-violation parameter δ CP in the neutrino sector The use of a single neutrino super beam source and half-megaton neutrino detector will optimize the efficiency and cost-effectiveness of a full program of neutrino measurements. If the value of sin 2 2 θ 13 happens to be larger than ~0.01, then all the parameters, including CP-violation can be determined in the VLB program presented here.
Advantages of a Very Long Baseline • neutrino oscillations result from ν µ DISAPPEARANCE 2 L / 4E) the factor sin 2 ( ∆ m 32 modulating the ν flux for each flavor (here ν µ disappearance) BNL-HS 2540 km 250 • the oscillation period is directly sin 2 2 θ 23 = 1.0 proportional to distance and ∆ m 2 32 = 2.5e-3 eV 2 200 inversely proportional to energy 1 MW, 0.5 MT, 5e7 sec • with a very long baseline actual No oscillations: 13290 evts 150 oscillations are seen in the With oscillations: 6538 evts data as a function of energy Background: 1211 evts 100 • the multiple-node structure of the very long baseline allows the 2 to be precisely measured ∆ m 32 50 by a wavelength rather than an amplitude (reducing systematic 0 0 1 2 3 4 5 6 7 8 9 10 errors) Reconstructed ν Energy (GeV)
Baseline Length and Neutrino Energy • for a fixed phase angle, e.g. π /2, the ratio of distance to energy is fixed (see sloped lines in Figure) • the useful neutrino energy range in a beam derived from a proton production source is restricted: below ~1 GeV by Fermi mom. in the target nucleus above ~8 GeV by inelastic ν interactions background • these conditions prescribe a needed baseline of greater than 2000 km from source to detector • by serendipity, the distance from BNL to the Homestake Mine in Lead, SD is 2540 km
Mass -ordering and CP-violation Parameter δ CP • the CP-violation parameter δ CP can be measured in the VLB exp. And is relatively insensitive to the value of sin 2 2 θ 13 • the mass-ordering of the neutrinos is determined in the VLB exp; ν 1 < ν 2 < ν 3 is the natural order but ν 1 < ν 3 < ν 2 is still possible experimentally; VLB determines this, using the effects of matter on the higher-energy neutrinos
AGS Intensity History 1 MW AGS
Total Accelerated Protons at the AGS 1.2 × 10 20 1.2E+20 red = SEB , blue = FEB ) 1.0 × 10 20 Total accelerated protons 1.0E+20 0.8 × 10 20 8.0E+19 0.6 × 10 20 6.0E+19 accelerated protons ( 0.4 × 10 20 4.0E+19 0.2 × 10 20 2.0E+19 0 0.0E+00 Jan-93 Jan-94 Jan-95 Jan-96 Jan-97 Jan-98 Jan-99 Jan-00 Jan-01 Jan-02 Slow extracted beam (Kaon decay) Fast extracted beam (g-2) Note: Lower total accelerated protons in later years due to much shorter running time
AGS Upgrade to 1 MW To RHIC To Target Station High Intensity Source plus RFQ 200 MeV Drift Tube Linac BOOSTER AGS 1.2 GeV → 28 GeV 200 MeV 0.4 s cycle time (2.5 Hz) 400 MeV Superconducting Linacs 800 MeV 1.2 GeV 0.2 s 0.2 s � 1.2 GeV superconducting linac extension for direct injection of ~ 1 × 10 14 protons low beam loss at injection; high repetition rate possible further upgrade to 1.5 GeV and 2 × 10 14 protons per pulse possible (x 2) � 2.5 Hz AGS repetition rate triple existing main magnet power supply and magnet current feeds double rf power and accelerating gradient further upgrade to 5 Hz possible (x 2)
AGS 1 MW Upgrade and SC Linac Parameters Superconducting Linac Parameters Proton Driver Parameters Linac Section LE ME HE Item Value Total beam power 1 MW Av Beam Pwr, kW 7.14 14.0 14.0 0.4 × 10 13 Av Beam Curr, mA 35.7 35.7 35.7 Protons per bunch K.E. Gain, MeV 200 400 400 Beam energy 28 GeV Frequency, MHz 805 1610 1610 Injection turns 230 Total Length, m 37.82 41.40 38.32 Average beam current 38 mA Accel Grad, MeV/m 10.8 23.5 23.4 Repetition rate 2.5 Hz norm rms ε , π mm-mr 2.0 Cycle time 400 ms 2.0 2.0 Pulse length 0.72 ms 9.6 × 10 13 Number of protons per fill Chopping rate 0.75 Number of bunches per fill 24 Linac average/peak current 20/30 mA
Neutrino Beam Production •1 MW He gas-cooled Carbon- carbon target •New horn design •Target on down-hill slope for long baseline experiment •Beam dump well above ground water table to avoid activation
Neutrino Spectrum at 1 km Low Z (Carbon) target seems feasible for 1 MW, 28 GeV proton beam. Thin low Z target minimizes reabsorption which increases flux of high energy neutrinos
Upgrade to 4MW Raise SCL energy to 1.5 GeV, AGS repetition rate to 5Hz 1. with 2 x 10 14 ppp. Add post AGS accelerator to 40 GeV, raise AGS rep rate to 2. 5 Hz with 1.4 x 10 14 ppp.
Chronology of BNL Super Neutrino Beam Program 1. June/01 US Feasibility Study-II of a Neutrino Factory 2. Dec/01 Establishment of BNL Neutrino Working Group for 2MW neutrino superbeam 3. April/02 Presentation of HIHB Hadron Beam Workshop at FNAL 4. June/02 Presentation of NuFact 2002 Workshop, London 5. Oct/02 BNL NWG Report-I 6. Feb/03 HEPAP Facility Subcommittee presentation
Chronology of BNL Super Neutrino Beam Program (cont’d.) 7. April/03 BNL NWG Report-II 8. Aug/03 Phys. Rev. D68, 012002 (2003) 9. Nov/03 NBI2003, KEK 10. Dec/03 UCLA Workshop on Detector 11. April/04 BNL Workshop on Source
Conclusions 1. The VLBL approach is capable of resolving most of the neutrino physics issues, including that of cp violation. 2. The feasibility has been demonstrated for a 1MW upgrade for the AGS 3. It is possible to further upgrade the AGS to 4MW Such a high power proton driver is essential for very long base line neutrino experiment and also for the neutrino factory.
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