STATUS OF BNL SUPER NEUTRINO BEAM PRORAM W. T. Weng Brookhaven - - PowerPoint PPT Presentation

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 ∆m32

2 and sin22θ23

• detection of the oscillation of νµ → νe and measurement of sin22θ13
• measurement of ∆m21

2 sin22θ12 in a νµ → νe appearance mode,

independent of the value of θ13

• verification of matter enhancement and the sign of ∆m32

2

• determination of the CP-violation parameter δCP 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

• f neutrino measurements. If the value of sin22θ13 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

νµ DISAPPEARANCE

50 100 150 200 250 1 2 3 4 5 6 7 8 9 10

Reconstructed ν Energy (GeV)

BNL-HS 2540 km sin22θ23 = 1.0 ∆m2 32 = 2.5e-3 eV 2 1 MW, 0.5 MT, 5e7 sec No oscillations: 13290 evts With oscillations: 6538 evts Background: 1211 evts

• neutrino oscillations result from

the factor sin2(∆m32

2 L / 4E)

modulating the ν flux for each flavor (here νµ disappearance)

• the oscillation period is directly

proportional to distance and inversely proportional to energy

• with a very long baseline actual
• scillations are seen in the

data as a function of energy

• the multiple-node structure of the

very long baseline allows the ∆m32

2 to be precisely measured

by a wavelength rather than an amplitude (reducing systematic errors)

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 δCP

• the CP-violation parameter δCP can

be measured in the VLB exp. And is relatively insensitive to the value

• f sin22θ13
• the mass-ordering of the neutrinos

is determined in the VLB exp; ν1 < ν2 < ν3 is the natural order but ν1 < ν3 < ν2 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

0.0E+00 2.0E+19 4.0E+19 6.0E+19 8.0E+19 1.0E+20 1.2E+20

Jan-93 Jan-94 Jan-95 Jan-96 Jan-97 Jan-98 Jan-99 Jan-00 Jan-01 Jan-02 accelerated protons ( red = SEB , blue = FEB )

0.8 × 1020 0.6 × 1020 0.4 × 1020 0.2 × 1020 Total accelerated protons 1.0 × 1020 1.2 × 1020

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

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 0.2 s 200 MeV 1.2 GeV superconducting linac extension for direct injection of ~ 1 × 1014 protons

low beam loss at injection; high repetition rate possible further upgrade to 1.5 GeV and 2 × 1014 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

Linac Section LE ME HE Av Beam Pwr, kW 7.14 14.0 14.0 Av Beam Curr, mA 35.7 35.7 35.7 K.E. Gain, MeV 200 400 400 Frequency, MHz 805 1610 1610 Total Length, m 37.82 41.40 38.32 Accel Grad, MeV/m 10.8 23.5 23.4 norm rms ε, π mm-mr 2.0 2.0 2.0

Proton Driver Parameters

Item Value Total beam power 1 MW Protons per bunch 0.4×1013 Beam energy 28 GeV Injection turns 230 Average beam current 38 mA Repetition rate 2.5 Hz Cycle time 400 ms Pulse length 0.72 ms Number of protons per fill 9.6 ×1013 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

1.

Raise SCL energy to 1.5 GeV, AGS repetition rate to 5Hz with 2 x 1014ppp.

2.

Add post AGS accelerator to 40 GeV, raise AGS rep rate to 5 Hz with 1.4 x 1014ppp.

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.