Very Long Baseline experiment with a Super Neutrino Beam Brookhaven National Laboratory

April 7, 2003 M. Diwan

Very Long Baseline experiment with a Super Neutrino Beam

Brookhaven National Laboratory(work of the neutrino working group)

Presented to theDPF 2003, Philadelphia

(Ref: hep-ph/0303081)

Milind V. Diwan(Stephen Kahn)

Brookhaven National Laboratory

Philadelphia, PAApril 7, 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

the mass scales among the neutrinos may help us understand the

evolution of all particle masses down from the Planck scale

if CP-violation is observed in the neutrino system, it will be quite large

and may drive the much smaller CP-violation in the quark sector

the early universe implications of large CP-violation in the neutrino

sector might help explain the mass asymmetry in the present universe


Physics Goals of theVery 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 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 sin2213 happens to be larger than

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

the VLB program presented here.


BNL Homestake Super 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


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)


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


Prob( to e) through earth

• Above 3 GeV matter enhancement by about factor of 2.

• 1-3 GeV : small matter effect, large CP effect.

• <1.5 GeV: m221

contribution increases at low energy.

• Very long baseline separates physics effects.


VLB Application to Measurement of m322

the multiple node method of the VLB 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 VLB method (a combination of target power and geographical circumstances limit other potential competitors) other planned experiments can’t achieve the VLB 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 VLB

experimental method


e Appearance Measurements (Cont.)

even if sin2213 = 0, the current

best-fit value of m212 = 7.3x10-5

induces a e appearance signal

the size of the e appearance signal

above background depends on the

value of m212; the figure left

indicates the range of possible

measured values for the e

yields above background for various assumptions of the final value of

m212


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


Possible limits on sin2213 versus CP

• For normal mass ordering limit on sin2213 will be 0.005 for no CP

Any experiment with horn focused beam is unlikely to do better.

• If reversed mass ordering then need to run antineutrinos


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.


Resolution on CP phase

• Resolution gets better rapidly as m21

2 becomes larger.

• Resolution of 20 deg as long as signal sufficiently above background.


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


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

the half-megaton detector was not detailed in this presentation but

we note that the UNO detector has all the properties needed for the VLB

neutrino program and offers important and compelling physics beyond

the neutrino oscillations work.

neutrino only running, low sensitivity to systematics,

high sensitivity to mass ordering, broad spectrum of physics.

This plan received high marks from HEPAP facilities committee in February.


Questions From the Subcommittee

What size collaboration is needed to construct the accelerator and to construct and do physics with the detector?

The accelerator upgrades and most of the technical design and construction work for the BNL site work would be accomplished by the staff of the C-A Department;

the equivalent questions for the detector are left to Prof. Jung; we have estimated15% EDIA, or $33 M over 5 years, amounting to an average design/construction professional staff of 66 FTE (physicists are not counted in the EDIA budget). The detector collaboration is expected to number between 300 and 500 physicists (estimated by Prof. Jung).

What is the timeline/schedule for the accelerator and beamline?

The technically (not budget) limited schedule would comprise a 3-year R&D period (FY04-06) followed by a 5-year construction period (FY07-FY11); the critical path

would definitely be the R&D to develop the superconducting RF cavities and RFpower system. All the other systems would require less R&D time. There are nonovel or unproven technologies in the accelerator and neutrino beam concept.


Questions From the Subcommittee (Cont.)

What is the estimated total project cost (including the proton driver, beamline, and detector = UNO)? Please give the basis of the cost estimate.

AGS Upgrade & SC Linac $156.8M (C-AD staff, recent SNS and BNL experience)Neutrino Beam Cost 61.7M (C-AD/Phys. Dept. staff, recent BNL experience)EDIA, Conting., Proj. G&A 150.0M (BNL project experience and current rates)

Total Estimated Cost (TEC) $368.5M (fully burdened)

3 yrs R&D ($1M, 3M, 5M) 9.0M (estimated accelerator R&D in FY04, 05, 06) Pre-ops, starting in FY09 12.0M (this would accomplish the needed pre-ops)

Total Project Cost (TPC) $389.5M (fully burdened)

These estimates are provided in FY 2003 dollars and are for the Accelerator and Super Neutrino Beam elements only. Prof. Jung will provide the cost estimate forthe UNO Detector which we use as the basis for our physics calculations.

The basis of estimate comprises current costs that C-AD and BNL engineers and physicists derive from recent and ongoing BNL projects. The level of EDIA isscaled from recent BNL projects in HENP areas of DOE.

Very Long Baseline experiment with a Super Neutrino Beam Brookhaven National Laboratory

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