very long baseline experiment with a 1 mw neutrino beam brookhaven national laboratory

July 22, 2003 M. Diwan

Very Long Baseline experiment with a 1 MW Neutrino Beam

Brookhaven National Laboratory(work of the BNL neutrino working groupUpenn, Utexas, StonyBrook, Princeton)

Presented to theBSA Review committee

(Ref: Diwan et al., PRD68, 012002, 2003)

Milind V. Diwan

Brookhaven National Laboratory

New York, NYJuly 22, 2003


Physics Importance of Neutrino Oscillations

Complete measurement of the neutrino oscillation parameters is a physics goal of fundamental importance:

Neutrinos are fundamental particles whose full description in terms of

mass and mixing parameters is basic to the progress of particle physics

Neutrinos may have a unique role in particle physics:

They allow direct measurement of the fundamental.

Their mass scales and other properties are so different that perhaps

they allow us to understand Plank scale physics.

If neutrinos are observed to violate CP in a big way then they may be

driving the much smaller CP-violation in the quark sector and the

Baryon Asymmetry of the Universe.


Current neutrino picture

• Large mixings except for Ue3.

• No information on Ue3

• No knowledge of phases in the mixing.


Mass differences

• Absolute scale of neutrino mass known to be less than 2 – 3 eV.

• Known from atmospheric neutrino data: m2

31=m23-m2

1~ (+/-)0.0025 eV2

• Known from solar neutrinos and reactors: m2

21=m22-m2

1~ 0.000073 eV2

• Both with large errors and no knowledge of sign of m2

31


Physics Goals of the BNLVery Long Baseline Neutrino Program

We introduce a plan to provide the following goals in a single facility:

precise determination of the oscillation parameters m322 and sin2223

detection of the oscillation of e and measurement of sin2213

measurement of m212 sin2212 in a e appearance mode, can be

made if the value of 13 is zero

verification of matter enhancement and the sign of m322

determination of the CP-violation parameter CP in the neutrino sector

The use of a single neutrino intense 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 sin2213 happens to be larger than

~0.01, then all the parameters, including CP-violation can be determined in

the BVLB program presented here.

BNL-Very-Long-BaseLine (BVLB)


Competing ideas

• Use narrow band beam to observe e

• Make neutrino factory to observe e

• Both approaches focus on lowering background using a better beam.

• Disadvantage: neither will see oscillatory pattern in energy spectrum. Will most likely need another step to achieve sufficient physics breadth.

• For the next stage of CP violation both must run with antineutrinos and also build detectors at multiple baselines.


BNL Homestake 1 MW Neutrino Beam

2540 km

Homestake BNL

28 GeV protons, 1 MW beam power500 kT Water Cherenkov detector5e7 sec of running, Conventional Horn based beam


Neutrino spectrum from AGS

• Proton energy 28 GeV• 1 MW total power• ~10

14 proton per pulse• Cycle 2.5 Hz• Pulse width 2.5 mu-s• Horn focused beam with

graphite target• 5x10-5 /m2/POT @ 1km• 52000 CC events.• 17000 NC events.


Advantages of a Very Long Baseline

DISAPPEARANCE

0

50

100

150

200

250

0 1 2 3 4 5 6 7 8 9 10

Reconstructed Energy (GeV)

BNL-HS 2540 km

sin2223 = 1.0

m2 32 = 2.5e-3 eV2

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(m322 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

m322 to be precisely measured

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


VLB Application to Measurement of m322

the multiple node method of the BVLB measurement is illustrated by comparing the BNL 5-year measurement precision with the present Kamiokande results and the projected MINOS 3-year measurement precision; all projected data include both statistical and systematic errors there is no other plan, worldwide, to employ the BVLB method (a combination of target power and geographical circumstances limit other potential competitors) other planned experiments can’t achieve the BVLB precision


e Appearance Measurements

a direct measurement of the

appearance of e is important;

the VLB method competes well with any proposed super beam concept

for values > 0.01, a measurement

of sin2213 can be made (the

current experimental limit is 0.12)

for most of the possible range of

sin2213, a good measurement of

13 and the CP-violation parameter

CP can be made by the BVLB

experimental method


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 sin2213

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


Comparisons to other projects

• BNL-HS has reach to lower Dm2 and a larger physics agenda.

• No conventional beam experiments can beat the background from beam contamination

• Plot ignores CP, multi-node, matter effects


Important Observations

• If signal is well above background CP resolution is indep. of sin2213

• Wide band beam and 2540 km eliminate many parameter correlations.

• For 3-generation mixing only neutrino running is needed.


AGS Target Power Upgrade to 1 MW

the AGS Upgrade to provide a source for the 1.0 MW Super Neutrino Beam will cost $265M FY03 (TEC) dollars


AGS 1 MW Upgrade and SC Linac Parameters

Proton Driver Parameters

Item Value

Total beam power 1 MWProtons per bunch 0.41013

Beam energy 28 GeVInjection turns 230Average beam current 38 mARepetition rate 2.5 HzCycle time 400 msPulse length 0.72 msNumber of protons per fill 9.6 1013

Chopping rate 0.75Number of bunches per fill 24Linac average/peak current 20/30 mA

Superconducting Linac Parameters

Linac Section LE ME HE

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


1 MW Target for AGS Super Neutrino Beam

1.0 MW He gas-cooled, Carbon-Carbon target for the Super Neutrino Beam


Super Neutrino Beam Geographical Layout

BNL can provide a 1 MW capable Super Neutrino Beam for $104M FY03 (TEC) dollars

the neutrino beam can aim at any site in the western U.S.; the Homestake Mine is shown here

there will be no environmental issues if the beam is produced atop the hill illustrated here and the beam dumped well above the local water table construction of the Super Neutrino Beam is essentially de-coupled from AGS and RHIC operations


3-D Neutrino Super Beam Perspective


Detector

• Requirements: – 500 kTons fiducial mass– ~10 % energy resolution on quasielastic events– Muon/electron discrimination at <1%– 1, 2, 3 track event separation– Showering NC event rejection at factor of ~15


NC events have a shape that falls in Q2 and visible energy regardless of neutrino energy.

A 1-4 GeV neutrino beam and 2500 km ideal because background is naturally low at 3 GeV peak.


Detector choices

• Liquid Argon TPC– 100 kT module never

been built. Too large a step from current 300ton.

– Needs detailed simulations to make sure there are no hidden pitfalls, but should perform adequately.

• Water Cherenkov– 50 kT SuperK is

existence proof.– Current understanding

of background rejection: need another factor of 3 to 5 in the 1-2 GeV range.

– Could additional imaging capability help? (Aquarich concept by Ypsilantis)


Conclusions

• Measurement of the complete set of neutrino mass and mixing parameters is very compelling for the advance of particle physics

• The Very Long Baseline method, utilizing a 1 MW Super Neutrino Beam from BNL’s AGS, coupled with a half-megaton water Cerenkov detector

in the Homestake Mine in Lead, SD, offers a uniquely effective plan

• Work continues to understand the best detector design.

• Detector has applications far beyond neutrino oscillations.

• A deep underground 500 kT detector with the described performance

characteristics will be a unique facility for Physics.


Big Issues

• Do nothing but wait for JHF-SK ?

• Only do a sin2213 experiment. Doesn’t matter how long it takes ? >10 yrs.

• Perform a quick reactor based sin2213 experiment. Say 5 years ?

• Keep working on neutrino factory. Ignore all else.• What is the best thing for particle physics from

programmatic and funding point of view ?

very long baseline experiment with a 1 mw neutrino beam brookhaven national laboratory

Documents

bnl neutrino

neutrino factory

neutrino sectorthe use

atmospheric neutrino

oscillation of nm ne

focused beam

better beam

stage of cp violation