Superbeams Deborah Harris Fermilab July 26, 2004 NuFact’04 Osaka University

Superbeams

Deborah HarrisFermilab

July 26, 2004NuFact’04

Osaka University

26 July 2004 Deborah Harris, Superbeams, NuFact04 2

Outline of this Talk

• Goals for the Next Steps• Why Superbeams are a Challenge• Beamline Strategies• Detector Strategies (see Strolin tomorrow!)• Prospects

– Near Term: T2K and NOA

– Why Two Beams are better than one…

– Far Term: Lots of other ideas…

• Summary


What do we want to know?

• Known:– Two large mixing angles, maybe one small– 3 independent mass splittings, one is positive– Absolute neutrino mass limits

• Unknown:– Absolute Mass Scale– How many ’s are there?– Mass Hierarchy?– Is CP Violated?– Are ’s their own antiparticles?

Mena&Parke, hep-ph/0312131


Definition of Mixing Angles

• Need to measure e to transitions at atm-scale baseline/energy


What happens when e’s pass through the earth?

22

22

22

)2cos(2sin

)2cos(2sin

2sin2sin

xLL

x

M

M

“Raises potentialEnergy for e’s andAnti-e’s separately”

nm

EnGx eF

2

22

electron densityin the earth

Wolfenstein, PRD (1978)


Designing a Neutrino Experiment

• Currently: pin down or eliminate m2

• Next: look for e / transitions at m2atm

– CP violation in absence of matter effects

– Matter effects in absence of msol2

13

2

sin

sin

)()(

)()(

E

Lm

PP

PPsol

ee

ee

Ree

ee

E

E

PP

PP

2)()(

)()(

GeVE

nG

mE

R

eF

atmR

11

22

2


Making a Neutrino Beam

• Conventional Beam

• Beta Beam

• Neutrino Factory

Detector Needs


Conventional Beam Challenges

• CHOOZ tells us it’s a small effect (<5%)

• Unavoidable contamination of e in beam

– From decays– At high enough p energies, K enters too!

• KL→ e –e and KL→ e +e

• Can mistake

0, or ± for e

What is so hard about →e


Two Approaches: Narrow and Broad

• Narrow Band Beams– Lower backgrounds under peak from e and NC– But flux is narrower than oscillation maximum!– Most sensitive limits per MW*kton– Examples: T2K, NOA, CNGT

• Broad Band Beams– Higher event rates – In some cases actually measure shape of oscillations – Higher e backgrounds at any one energy– Examples: BNL LOI, FeHo, CERN SPL


“Off Axis” Neutrino Beams

• First Suggested by Brookhaven (BNL 889)• Take advantage of Lorentz Boost and 2-body

decays• Concentrate flux at one energy• Lower NC and e backgrounds at that energy (3-body decays)


Detector Options

• Water Cerenkov

• Scintillator Calorimetry

• Liquid Argon TPC


Water Cerenkov

• Excellent particle ID for single-ring events• Most massive detector built to date• More problematic for multi-ring events• Multi- events can fake single-ring events

Being consideredfor higher and higher energies

because of low energy

capabilities…(see Strolin’s talk)

0 o

r e?

SuperK event displays courtesy Mark Messier


Scintillator Calorimetry• Calorimeter with <X0

sampling can do – e/ separation by looking for

gaps after event vertex

– e/ separation from track characteristics

• Can see all particles, good energy reconstruction at all energies

• Events at right: all scintillator, 1 cell equals:– 4.9 cm horizontal axis

– 4.0 cm vertical axis

+ A -> p + 3± + 0 +

e+A→p + - e-

+ A -> p +-

Cooper, June 2004 PAC


Liquid Argon TPC

• Electronic Bubble Chamber

• Lots of recent progress with

event reconstruction

• Test runs at Pavia and CERN producing lots of pretty events

• Looking forward to seeing how detector measures CNGS beam

• Looking to “industrialize” design

AB

BC

K+

µ+

Run 939 Event 46

A

B

C

D

K+

µ+

e+

e-, 15 GeV, pT=1.16 GeV/c R

ubbi

a, N

uIN

T04


In Praise of Near Detectors

• To make precise measurements,need – Background cross sections

– Signal (CC!) cross sections

MINERA event display

Need Dedicated Measurements in fine-grained detectors

(see D.Casper’s talk on Friday)

Dat

a co

mpi

led

by G

.Zel

ler,

hep

-ex/

0312

061

proton

A→

A

N→

pN

’


First Step: seeing if 13 is non-zero

• T2K Tokai to Kamioka– 295km, 1st osc. maximum– 50kton Water Cerenkov (SK)– New 0.8MW proton Source:

J-PARC

OAB2.0degOAB2.5degOAB3.0deg

December, 2003

12/2003 Exp’t approved2008 Accelerator operating2009 Physics Running


T2K Detector Suite

Several jobs, several detectors:

1. Verify beam direction2. Measure and e fluxes

with high statistics 3. Measure background and

signal cross sections4. Eventually, verify

background rates in “identical” detector at 2km

Hay

ato,

20

04


T2K Physics ReachH

ayat

o,

2004


NOA• Use Existing NuMI beamline• New Detector 12km off axis• 820km shows best compromise

between reach in 13 and matter effects

• PAC recommendation “The Committee strongly endorses the

physics case for the NOA detector, and would like to see NOA proceed on a fast track that maximizes its physics impact.”

• Beam ready first—start taking data with fraction of the detector

• New Studies show all scintillator has better reach per dollar

Assuming m2=2.5x10-3eV2

Messier, 2004


NOA Physics Reach

50kton baseline detector 50kton baseline

detector

Because of CP and matter effects, “reach” vs. sin2 213 will vary…

Fel

dman

, Asp

en P

AC

200

4


Oscillation Probabilities

• For any one energy and baseline, you don’t get the whole story…• Need two energies, or two baselines, and at least one baseline needs to be long

enough to see matter effects• First question: what do you get if you add more protons and detector to first

generation experiments?

P(→e)=P1+P2+P3+P4

Minakata &

Nunokaw

a JHE

P 2001


What does 2 get you that 1 doesn’t?

•J-PARC Upgrade:0.7 to 4MW proton source

Beamline preparations now

50kton to 500kton (Hyper-K)Study new light collection technology

•NOA Upgrade:0.25 to 2MW proton source

Proton Driver CD-0 Machine and Physics Study Possible second detector at 710km, 30km off axis

Feldman, Aspen 2004


CP Violation at T2Hyper-K

no BGsignal stat only

(signal+BG) stat only

stat+2%syst. stat+5%syst.

stat+10%syst.

CHOOZ excludedsin2213<0.12@m31

2~3x10-3eV2

T2K 3 discovery

3 CP sensitivity : ||>20o for sin2213>0.01 with 2% syst.

4MW, 540kt2yr for

6~7yr for

m212=6.9x10-5eV2

m322=2.8x10-3eV2

12=0.59423=/4

T2K-I 90%

Kobayashi, 2004


Next Steps depend on First Steps

• LSND Confirmed by MiniBooNE? – Lots of new shorter baseline beamlines needed– CP violation in →becomes more important

• Both T2K and NOA see no evidence for 13≠0?– Upgrade either (or both) to get most sensitive search

• Either T2K or NOA see a hint of 13≠0?– Lots of new ideas, depends on who sees what

• Is signal in neutrinos or antineutrinos?• Does one see it but not the other?

• No matter what we know we will need:– Need protons and targets that can accept them– Need better background rejection with high efficiency


Fermilab to Homestake• Based on 2MW at 120GeV, +2MW at

8GeV• Several off axis beams + 1 on axis

beam to give broad spectrum• May be easiest way to get to 4MW of

proton power• Very preliminary, more of a show of

flexibility given enough protons~200M

~8m

~4m

30 mR maximum off axis

120 GeV protons8 GeV

protons


Fermilab to Homestake Physics Reach

Considering Different Detectors1. 500kT Water Cerenkov (shown here)2. Liquid Argon TPC3. All-Scintillator Detector (NOA)

Michael, Snowmass 2004

Water Cerenkov

Disappearance

e Appearance

Water Cerenkov


Brookhaven to Homestake• 28GeV AGS upgrade to 1MW

(2MW) cf current 0.1MW• Wide band beam (0.5~6GeV)• L=2,540km• Mton UNO (alternative option:

Liquid Argon TPC)• ~13,000 CC/year/500kt• Cover higher osc. maxima

Recent ProgressAGS Upgrade path solidifiedCivil Construction DevelopedTargeting R&D Better WC simulations— investigating ways to overcome backgrounds(1 degree off-axis capability)

Chiaki Yanagisawa

Brett Viren


Brookhaven to Homestake Physics Reach

Studies with agressive Detector MC: even with only data, CP violation and mass hierarchy are visible

in some regions of parameter space.

Normal hierarchy Reversed hierarchy

But with both and running, CP precision much higher

Diwan, 3/2004 APS study meeting


Beta-Beam and SPL at CERN• 4MW 2.2GeV Superconducting

Proton Linac (SPL) @ CERN• Low energy wide band (E~0.3GeV)• L=130km• Water Cerenkov (400kt) or LAr TPC• ~18,000 nm CC/year/400kt• SPL in R&D, UNO in conceptual

design• Clear overlap between SPL target

and neutrino factory target

Beta beam uses knownIsolde technology…Progress on design, andradiation shielding

Schematic of Large detectors in Frejus tunnel (Mosca, CERN 2004)


Beta-Beam and SPL Physics Reach

Burguet-Castel et al,hep-ph/0312068

L(km) E(GeV)

60/100 130 0.23/0.37

350/580 730 1.4/2.2

1500/2500 3000 5.8/9.4

Results below for combining Conventional and beta-beams

But also physics study has been doneTo look at higher energy beta-beamsAs well—feasibility studies to follow…

Mezzetto, NuFact03


Summary• Two complementary steps right around the corner

– T2K– NOA

• After that, we know we need more protons—many proton driver

upgrade paths – Fermilab– J-PARC– Brookhaven– CERN SPL

• Plenty of important measurements to make along the way

– Cross Sections (MINERA,K2K Scibar)• Next superbeam to build depends on

what the first superbeams find

Documents

Superbeams Deborah Harris Fermilab July 26, 2004 NuFact’04 Osaka University