1. STATUS OF BNL SUPER NEUTRINO BEAM PRORAM W. T. Weng Brookhaven National Laboratory NBI2003, KEK November 7-11, 2003

2. 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

3. 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  23  detection of the oscillation of   e and measurement of sin 2 2  13  measurement of  m 21 2 sin 2 2  12 in a   e appearance mode, independent of the value of  13  verification of matter enhancement and the sign of  m 32 2  determination of the CP-violation parameter  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  13 happens to be larger than ~0.01, then all the parameters, including CP-violation can be determined in the VLB program presented here.

4. Advantages of a Very Long Baseline  neutrino oscillations result from the factor sin 2 (  m 32 2 L / 4E) modulating the flux for each flavor (here  disappearance)  the oscillation period is directly proportional to distance and inversely proportional to energy  with a very long baseline actual oscillations are seen in the data as a function of energy  the multiple-node structure of the very long baseline allows the  m 32 2 to be precisely measured by a wavelength rather than an amplitude (reducing systematic errors)

5. Baseline Length and Neutrino Energy  for a fixed phase angle, e.g.  /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 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

6. Mass -ordering and CP-violation Parameter  CP  the CP-violation parameter  CP can be measured in the VLB exp. And is relatively insensitive to the value of sin 2 2  13  the mass-ordering of the neutrinos is determined in the VLB exp; 1 < 2 < 3 is the natural order but 1 < 3 < 2 is still possible experimentally; VLB determines this, using the effects of matter on the higher-energy neutrinos

7. AGS Intensity History 1 MW AGS

8. Total Accelerated Protons at the AGS 0.8  10 20 0.6  10 20 0.4  10 20 0.2  10 20 0 Total accelerated protons 1.0  10 20 1.2  10 20 Slow extracted beam (Kaon decay) Fast extracted beam (g-2) Note: Lower total accelerated protons in later years due to much shorter running time

9. AGS Upgrade to 1 MW 200 MeV Drift Tube Linac BOOSTER High Intensity Source plus RFQ Superconducting Linacs To RHIC 400 MeV 800 MeV 1.2 GeV To Target Station AGS 1.2 GeV  28 GeV 0.4 s cycle time (2.5 Hz) 0.2 s 200 MeV l 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) l 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)

10. AGS 1 MW Upgrade and SC Linac Parameters Proton Driver Parameters ItemValue Total beam power1 MW Protons per bunch0.4  10 13 Beam energy28 GeV Injection turns230 Average beam current38 mA Repetition rate2.5 Hz Cycle time400 ms Pulse length0.72 ms Number of protons per fill9.6  10 13 Chopping rate0.75 Number of bunches per fill24 Linac average/peak current20/30 mA Superconducting Linac Parameters Linac Section LE ME HE Av Beam Pwr, kW7.1414.014.0 Av Beam Curr, mA35.735.735.7 K.E. Gain, MeV200400400 Frequency, MHz80516101610 Total Length, m37.8241.4038.32 Accel Grad, MeV/m10.823.523.4 norm rms ,  mm-mr2.02.02.0

11. 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

12. 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

14. Upgrade to 4MW 1. Raise SCL energy to 1.5 GeV, AGS repetition rate to 5Hz with 2 x 10 14 ppp. 2. Add post AGS accelerator to 40 GeV, raise AGS rep rate to 5 Hz with 1.4 x 10 14 ppp.

15. 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

16. 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

17. 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.