“Oscillazioni di neutrini alle nuove macchinebettoni/gdl/Mezzetto_cern_2904.pdf ·...

Mauro Mezzetto

Istituto Nazionale di Fisica Nucleare,

Sezione di Padova

“Oscillazioni di neutrini alle nuove macchine ”

• Oscillazioni di neutrini

• Come e quando

• Descrizione delle possibili facilities.

• Physics reach e qualche confronto.

CERN, 29 aprile 2004.M. Mezzetto, CERN, 29 aprile 2004. . 1

ν oscillations are the most important discovery in hep of the last 15 years.

They measure fundamental parameters of the standard model. Mixing angles, neutrino

masses and the CP phase δCP are fundamental constants of the standard model.

They are a probe of the GUT scales . The smallness of neutrino masses is connected to

the GUT scale through the see-saw mechanism.

They are directly linked to many fields in astrophysics and cosmology : baryogenesis,

leptogenesis, galaxies formation, dynamic of supernovae explosion, power spectrum of

energy anisotropies, etc.

They open the perspective of the measure of leptonic CP violation.

M. Mezzetto, CERN, 29 aprile 2004. . 2

If you are skeptical about that ....

Experimental articles with more than 500 cites in the last 15 years in the

QSPIRES database (at 04/04/03):

1 SK Evidence for Oscillation of Atmospheric Neutrinos. 17052 SCP Measurements of Ω and Λ from 42 High Redshift SN. 1311

3 SST Observational Evidence from SuperNovae for an

Accelerating Universe and a Cosmological Constant.

1293

4 COBE Structure in the COBE DMR First Year Maps. 1036

5 CDF Observation of TOP Quark Production in p− p Collisions. 930

6 D0 Observation of the Top Quark. 889

7 SK Atmospheric νµ/νe Ratio in the MultiGeV Energy Range. 751

8 Chooz Initial Results from CHOOZ. 6839 Boomerang A Flat Universe from High Resolution Maps of the CMB. 644

10 Chooz Limits on Neutrino Oscillations from the CHOOZ

Experiment.

635

11 Kamiokande Observation of a Small Atmospheric νµ/νe Ratio. 628

12 CLEO First Measurement of the Rate for the Inclusive b —> sγ. 618

13 SNO Measurement of the rate of νe + d –> p + p + e- ... 592

14 Homestake Measurement of the Solar νe Flux ... 565

15 LSND Evidence for νµ —> νe Oscillations from LSND. 56316 SK Measurement of a Small Atmospheric νµ/νe Ratio. 561

17 CDF Evidence for TOP Quark Production in p − p .... 550

18 SK Study of the Atm. ν Flux in the MultiGeV Energy Range. 547

19 IMB The νe and νµ Content of the Atmospheric Flux. 53520 SK Solar Neutrino Data Covering Solar Cycle 22. 504

21 LSND Neutrino Oscillations from LSND. 500


Most of the parameters are waiting to be measured

δm

m

m2

223

12 12

23

13

CP

θ

θ

νΣ

Mass hierarchy

Dirac/Majorana

θ

δ

ATMOSPHERICS

δ

δm223 = (2.0 +/- 0.4) 10 eV

2

SOLARS+KAMLAND

δm212

= (7 +/- 1) 10 eV2-5

ATMOSPHERICS

0.9 < sin22( 23θ ) < 1

SOLARS+KAMLAND

0.2 < sin2( 12θ ) < 0.5

CHOOZ LIMIT

13θ < 14 0

Addressed by a SuperBeam/Nufact experiment

BETA DECAY END POINT

mνΣ < 6.6 eV

-3


I Leptoni nel modello standard hanno caratteristiche MOLTO diverse dai quark

u ∼ 5 MeV c ∼ 1 GeV t ∼ 175GeV

d ∼ 8 MeV s ∼ 0.1 GeV b ∼ 5GeV

e ∼ 0.5 MeV µ ∼ 0.1 GeV τ ∼ 2GeV

νe ≤ O(1 eV ) νµ ≤ O(1 eV ) ντ ≤ O(1 eV )

Com’e’ possibile nello stesso modello generare rapporti di massa cosi’ diversi? ⇒ See-saw mechanism

Solar+Atmospherics indicano una matrice di mixing quasi bi-maximal, MOLTO DIFFERENTE dalla matrice CKM

(quasi diagonale)!

U =

⎛⎜⎜⎝

1 0 0

0 c23 s23

0 −s23 c23

⎞⎟⎟⎠

⎛⎜⎜⎝

c13 0 s13e−iδ

0 1 0

−s13eiδ 0 c13

⎞⎟⎟⎠

⎛⎜⎜⎝

c12 s12 0

−s12 c12 0

0 0 1

⎞⎟⎟⎠ ,

θ13 → 0 ⇒ La matrice 3x3 rimane un semplice prodotto di due matrici 2x2.

θ13 drives νµ → νe subleading transitions ⇒the necessary milestone for any subsequent search:

neutrino mass hierarchy and leptonic CP searches.


Sub leading νµ − νe oscillations

L (km)

<E >=1.00 GeVsin2(2θ13)=0.01sin2(2θ12)=0.8δm 2

13 =2.5E-3 eVδm 2

12 =7.E-5 eVδ=0

0 5000 10000 15000 20000 25000 30000

Solar peak

θ peak13

L (km)

δ=-π/2

JHFequivalentbaseline

CNGSequivalentbaseline

p(ν µ

ν e)

TotalSolarθ13CPevenCPodd

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0 50 100 150 200 250 300 350 400 450 500

p(ν µ

ν e)

22

p(νµ → νe) developed at the first order of matter effects

p(νµ → νe) = 4c213s

213s

223 sin2 ∆m2

13L

4Eθ13 driven

+ 8c213s12s13s23(c12c23cosδ − s12s13s23) cos

∆m223L

4Esin

∆m213L

4Esin

∆m212L

4ECPeven

− 8c213c12c23s12s13s23sin δ sin

∆m223L

4Esin

∆m213L

4Esin

∆m212L

4ECPodd

+ 4s212c

213c2

13c223 + s2

12s223s

213 − 2c12c23s12s23s13cosδ sin

∆m212L

4Esolar driven

− 8c212s

213s

223 cos

∆m223L

4Esin

∆m213L

4E

aL

4E(1 − 2s2

13) matter effect (CPodd)

where a = ±2√

2GF neEν = 7.6 · 10−5ρ[g/cm3]Eν [GeV ] [eV 2]


Almeno 4 fasi di esperimenti Long Baseline

1) 2001-2010. K2K, Opera, Icarus, Minos. Ottimizzati per confermare

il risultato sperimentale di SuperKamiokande/atmosferici, attraverso

νµ disappearance o ντ appearance. Limitato progresso nella misura dei

parametri. Non ottimizzati per νe appearance (θ13 )

2) 2009-2015. T2K (approvato), Minos off-axis, Chooz II. Ottimizzati per la

misura di θ13 (Chooz × 20) attraverso νe appearance o νe disappearance.

Misura di precisione dei parametri atmosferici. Sensitivita sulla fase di CP

δ molto limitata, anche combinando assieme i loro eventuali risultati.

3) 2015 - 2025. SuperBeam e/o Beta Beam. Migliore sensitivita su θ13 (Chooz × 200). A queste sensitivita θ13 e δ

sono cosi’ fortemente accoppiate che ogni sensitivita va definita nel piano (θ13 ,δ). Sensitivita su δ e mass hyerarchy.

4) Pericolosamente vicino al mio orizzonte temporale. Neutrino Factories. Ultimate sensitivity sulla fase δ.

Misura di precisione di tutti i parametri dell’oscillazione di neutrini.


JHF-Japan Hadron Facility at Jaeri

Neutrino beam from the 50 GeV - 0.75 MW

proton beam at the Hadron Facility at Jaeri,

Japan.

Taken off-axis to better match the oscillation

maximum at the SuperKamiokande location

(295 km).

K2K T2K

6 · 1012 Protons per pulse 3 · 1014

2.2 s Cycle 3.4 s

12 GeV Proton energy 50 GeV

40 Events in SK per year (no osc.) 2200

1.5 Mean neutrino energy 0.8

0

50

100

150

200

250

300

350

400

0 1 2 3 4 5Eν (GeV)

ν µ N

CC (

/100

MeV

/22.

5kt/y

r)

ON AXIS

OA 20

OA 30


T2K νe appearance

OAB 2 νµ CC νµ NC νe CC Osc. νe

Generated in F.V. 10713.6 4080.3 292.1 301.61R e-like 14.3 247.1 68.4 203.7e/π0 separation 3.5 23.0 21.9 152.20.4 GeV< Erec < 1.2 GeV 1.8 9.3 11.1 123.2

05

1015202530354045

0 1 2 3 4 5Reconstructed E ν (GeV)

Expected Signal+BG

Total BG

BG from νµ

Sensitivity to θ13

10-4

10-3

10-2

10-1

10-3

10-2

10-1

1

90% C.L. sensitivities

JHF 5yearsWBBOAB 2deg.NBB 2GeVCHOOZ excluded

sin22θµe

∆m2 (

eV2 )

x20


After T2K, in the standard scenario

• θ13, discovery or precision measure

• Mass hierarchy

• Leptonic CP violation

Any major improvement of T2K will be extremely expensive:

• The proton driver is a next generation machine

• The detector is 10 times bigger of the second biggest: Minos.

• The designed close detectors system is very ambitious.

IPNS

1000

10000

100

10

1

0.01

0.1

0.1 1 10 100 1000 10000Energy (GeV)

AGS

CERN-PSFNAL-MI

U70

SPS

ISISTRIUMF

PSI(CW)

KEK-12GeV PS

Tevatron

This Project3 GeV

ExistingUnderconstruction

Power

KEK-500MeVBooster

Cur

rent

(A

)

SNS

Proposed

Materials-LifeSciences

1 MW

0.1 MW

ESS

Nuclear-ParticlePhysicsThis Project50 GeV

THE θ13 DILEMMAThe knowledge of θ13 is necessary to guarantee the conditions to measure δ and to optimize the facility.

Waiting for the T2K results (or Numi Off-Axis or Reactors) implies a 10 years delay.

If we wait and θ13 remains undetected we should consequently stop any further neutrino oscillation initiative (because of

the cost).

Any future initiative should have enough physics potential besides neutrino oscillations to justify the risk of starting the

Leptonic CP violation searches without any guarantee.


Leptonic CP

Two conditions to make Leptonic CP detectable:

• Solar LMA confirmed (Done! now 5 < sin2 2θ12 < 10 · 10−5 eV 2 (3σ))

• θ13 ≥ 0.50 (see the following).

A big step from a θ13 search:

from p(νµ → νe ) = 0 to

⎧⎨⎩

p(νµ → νe ) = p(νµ → νe ) (direct CP)

p(νµ → νe ) = p(νe → νµ ) (T search)

This will require:

1. Neutrino beams of novel conception.

Super Beams

Neutrino Factory

Beta Beams

2. Detectors of unprecedent mass

3. Improved control of systematics ⇒ Dedicated experiments on neutrino cross-section, hadron

production, particle ID.


Detecting the δ phase at the Neutrino Factories

Aδ = [P (νe → νµ , δ = +π/2) − P (νe → νµ , δ = 0)]/[P (δ = +π/2) + P (δ = 0)]

Compare the measured νe → νµ oscillation probability, as a function of the neutrino energy Eν , to a “Monte-Carlo”

prediction of the spectrum in absence of δ-phase.

Problems: it’s model dependent, requires a precise knowledge of the other oscillation parameters, possible degeneracy

between solutions and strong correlation with the θ13 parameter.

ACP(δ) = [P (νe → νµ , δ) − P (νe → νµ , δ)]/[P (νe → νµ , δ) + P (νe → νµ , δ)]

Compare the appearance of νµ (νµ ) in a beam of stored µ+( µ−)decays as a function of the neutrino energy Eν .

Problems It must compete with the fake CP from matter effects. Run time is more than doubled: ν cross sections are half

the ν cross section and matter effects disfavor ν oscillations.

AT(δ) = [P (νe → νµ , δ) − P (νµ → νe , δ)]/[P (νe → νµ , δ) + P (νµ → νe , δ)]

Compare the appearance of νµ in a νe beam AND νe in a νµ beam as a function of the neutrino energy Eν .

Problems Electron charge must be measured in case of a neutrino factory experiment. Systematics of muon and electron

efficiencies must be kept to very small values.


Phase 3 Players

Facility Momentum Power Baseline Events Bacgkr.

Super Beams firing to a 20x SuperKamiokande like detector

BNL AGS 28 GeV/c 1 MW 2500 or 2990 Km 1115 126

JPARC Phase II 50 GeV/c 4 MW 295 Km 8237 1378

CERN SPL 2 GeV 4 MW 130 Km 3137 454

Beta Beams firing to a 20x SuperKamiokande like detector

νe 348 0.5

νe 3358 198

Neutrino Factories 40582 112

Event numbers are νe appearance at the Chooz limit (sin2 2θ23 = 0.12), δ = 0, 5 yrs running. JPARC phase II and

Nufact are taken from P. Huber, EPS 2003.


SuperBeams - JPARC phase 2

Upgrade the proton driver from 0.75 MW

to 4 MW

Upgrade SuperKamiokande by a factor

∼ 20 =⇒ HyperKamiokande

Both upgrades are necessary to address

leptonic CP searches.

Systematics at 2% are tight

4 MW at 50 GeV/c are tight

Target and optics at 4 MW are tight and

will require some compromise

T. Kobayashi, J.Phys.G29:1493(2003)

0

2

4

6

8

10

12

14

0 0.2 0.4 0.6 0.8 1sinδ

sin2 2

13 (x

10−2

)

m232=2.8x10-3

m122=6.9x10-5

23= /412=0.594

4MW, 540kt2+6.3years

θ

∆∆

θθ

π

No

syst

. err

.

2% o

n ba

ckgr

.

2% o

n ba

ckgr

. and

sig

nal


SuperBeams - BNL

• The very far detector detects the first and the second

oscillation maximum.

• The comparison of the two maxima can allow the

detection of θ13 , δ and sign(∆m2), without the need of

an antineutrino run.

• An original and powerful method to extract the mixing

matrix parameters

HOWEVER

• The very long baselines wastes the most critical

parameter of SuperBeams: statistics

• The spectrum analysis requires good control of energy

reconstruction in a critical energy range for Water

Cerenkov detector and for the cross section knowledge

• First maximum neutrinos are pion daughters while second

maximum neutrinos are kaon daughters.

νµ DISAPPEARANCE

0

50

100

150

200

250

0 1 2 3 4 5 6 7 8 9 10

Reconstructed ν Energy (GeV)

Eve

nts/

bin

BNL-HS 2540 km

sin22θ23 = 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

νe APPEARANCE

0

20

40

60

80

100

0 1 2 3 4 5 6 7 8 9 10

Reconstructed ν Energy (GeV)

Eve

nts

/bin

BNL-HS 2540 kmsin22θij (12,23,13) = 0.86/1.0/0.04∆mij

2 (21,32) = 7.3e-5/2.5e-3 eV2

1 MW, 0.5 MT, 5e7 sec

CP 135o: 591 evts

CP 45o: 449 evts

CP -45o: 300 evts

Tot Backg.: 146 evts

νe Backg.: 70 evts


SuperBeams - SPL ν beam at CERN

A feasibility study of the CERN possible developments

Decay Tunnel

νν

Possible Low Energy Super Beam Layout

Far Detector

Near Detector

20 m

130 km

10 6

10 7

10 8

10 9

10 10

10 11

10 12

10 13

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Eν(GeV)

ν/10

0 m

2 /20

MeV ν Flux Eν(GeV) (%)

νµ 3.23E+14 0.27

νe 2.16E+12 0.32 0.668

νµ 5.16E+12 0.28 1.598

νe 1.24E+10 0.29 0.004

Flux intensities at 50 km from the target

Flavour Absolute Flux Rel. Flux 〈Eν〉(ν/1023pot/m2) (%) (GeV)

νµ 3.2 · 1012 100 0.27

νµ 2.2 · 1010 1.6 0.28

νe 5.2 · 109 0.67 0.32

νe 1.2 · 108 0.004 0.29


H- RFQ1 chop. RFQ2RFQ1 chop. RFQ2 RFQ1 chop. RFQ2DTL CCDTL RFQ1 chop. RFQ2β 0.52 β 0.7 β 0.8 LEP-II dump

Source Low Energy section DTL Superconducting section

45 keV 7 MeV 120 MeV 1.08 GeV 2.2 GeV

3 MeV 18MeV 237MeV 389MeV

13m 78m 334m 345m

PS / Isolde

Stretching andcollimation line

Accumulator Ring

MW-Linac: SPL (Superconducting Proton Linac)

Re-use superconductingLEP cavities

EKIN = 2.2 GeVPower = 4 MWProtons/s = 1016

10 protons/year23


R. Garoby

Proposed RoadmapConsistent with the content of a talk by L. Maiani at the “Celebration of the Discovery of the

W and Z bosons”. Contribution to a document to be submitted to the DecemberCouncil (“CERN Future Projects and Associated R&D”).

Assumptions:• construction of Linac4 in 2007/10 (with complementary resources, before end of

LHC payment)• construction of SPL in 2008/15 (after end of LHC payments)

Task NameLINAC4

Design ref inmentConstructionCommissioningStart operation with PSB

SPLDesign ref inmentConstructionLinac4 displacement + commissioningStart operation as PS Injector

12/31

12/30

2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

Linac 4approval SPL

approvalLHC

upgrade


The Megaton detector

• Fiducial volume: 440 kton: 20 times SuperK.

• 60000 PMTs (20”) in the inner detector,

15000 PMTs in the outer veto detector.

• Energy resolution is poor for multitrack

events but quite adequate for sub-GeV

neutrino interactions.

• It would be hosted at the Frejus laboratory,

130 km from CERN, in a 106 m3 cavern to

be excavated.

The ultimate detector for proton

decay, atmospheric neutrinos, supernovae

neutrinos.


The Frejus project

• Italy and France actively involved in

promoting the construction of a million cubic

meter laboratory under the Frejus

• The rock caracteristics and the distance to

CERN make Frejus a unique opportunity to

build such a detector.

• The only possibility to build such a detector

is to have a worldwide collaboration,

including japanese and americans from

SuperKamiokande. (only one detector of

this size is reasonable in the world)

• The second highway tunnel excavation will

be finished in 2008

• This opens the possibility to dig the

laboratory at a very reduced price

• 3+3 years since then is the (optimistic)

schedule to have the detector ready.

-> a very large Laboratory to allow the installation of a Megaton-scale Cerenkov Detector ( 106 m3)

Present Tunnel

Future Safety Tunnel

Present Laboratory

Future Laboratory with Water Cerenkov Detectors


Interesting features of a low energy conventional neutrino beam.

ν beam:• 〈Eνµ 〉 0.25 GeV

• νe production by kaons largely suppressed by threshold effects.

νe in the beam come only from µ decays.

π+ −→ µ+νµe+νeνµ

⇒

they can be predicted from

the measured νµ CC

spectrum both at the close

and at the far detector with

a small systematic error of

∼ 2%.

Detector Backgrounds• Good e/π0 separation following the large π0 → γγ opening angle

• Good e/µ separation in a Cerenkov detector because µ are produced

below or just above the Cerenkov threshold.

• Charm and τ production below threshold.

Less exiting aspects of a lowenergy neutrino beam• Cross sections are small ⇒

large detectors are necessary in

spite of the very intense neutrino

beam.

• νµ production is disfavored for

two reasons:

– Smaller π− multiplicity at the

target.

– νµ /νµ cross section ratio is

at a minimum (1/5).

• Visible energy is smeared out by

Fermi motion


A comparison of CP sensitivities: Nufact vs. SuperBeam

CP sensitivity, defined as the capacity to separate at 99%CL max

CP (δ = π/2) from no CP (δ = 0).

Nufact and SPL-SuperBeam sensitivities computed with the same

conditions.

0

0.5

1

0 1 2 3 4 5 6 7 8

θ13

∆m

122 (

x10-4

) eV

2

Nufact

SuperBeam

Best LMA, hep-ph/0212127

(degrees)

The limiting factors for the SuperBeam at small

θ13 values are:

• The low flux of ν and their small cross

section. This limits the overall statistic.

• The beam related backgrounds that increase

the statistical errors, hiding the CP signal.

As an example for θ13 =3, δm212 =

0.7 · 10−4 eV 2, sin2 2θ12 = 0.8:

νµ beam νµ beam2 years 8 years

µCC (no osc) 36698 23320Oscillated events (total) 45 133Oscillated events (cp-odd) -84 53Intrinsic beam background 140 101Detector backgrounds 36 49


Conventional neutrino beams will hit their ultimate limitations.

BCT1

BCT2

SEMs Reflector

TunnelDecay

Iron Shield

Muon Pits

Earth

Al Collimator

Horn

TDX collimatorBe Target

450 GeV/c protons NOMAD

CHORUS

In a conventional neutrino beam, neutrinos are produced by pions (and kaons) generated by the proton beam interaction

on the target. Given the short life time of the pions (2.6 · 10−8s), they can only be focused (and charge selected) by means

of magnetic horns. Then they are let to decay in a decay tunnel, short enough to prevent most of the muon decays.

• Beside the main component (νµ ) at least 3 other neutrino flavours are present (νµ , νe , νe ), generated

by wrong sign pions, kaons and muon decays.

• Hard to predict the details of the neutrino beam starting from the primary proton beam, since it derives

from hadronic interactions.

• Difficult to tune the energy of the beam in case of ongoing optimizations.

• Difficult to manage the targets at very high proton intensities (Super Beams: conventional neutrino

beams where conventional targets would be evaporated).

All these problems are overcome if the neutrino parents can be collected, focussed and accelerated at a given energy.

This is impossible within the pion lifetime, but can be tempted within the muon lifetime (Neutrino Factories) or within some

radioactive ion lifetime(Beta Beams).


Beta Beam (P. Zucchelli: Phys. Lett. B532:166, 2002)

M. Lindroos and collaborators, see http://beta-beam.web.ch/beta-beam

SPL

Isol target& Ion source

DECAY RING

B = 5TL = 2500 m

PSB

EURISOL Existing at CERN

New RFQ

SPS

PS Linac

• 1 ISOL target to produce He6, 100 µA, ⇒ 2.9 · 1018 ion decays/straight session/year. ⇒ νe .

• 3 ISOL targets to produce Ne18, 100 µA, ⇒ 1.2 · 1018 ion decays/straight session/year. ⇒ νe .

• The 4 targets could run in parallel, but the decay ring optics requires:

γ(Ne18) = 1.67 · γ(He6).M. Mezzetto, CERN, 29 aprile 2004. . 24

Fluxes

0

500

1000

1500

2000

2500

3000

3500

4000

4500

x 10 7

0 0.2 0.4 0.6 0.8 1

Eν (GeV)

ν/m

2 /20

meV

SPL νµ

SPL ν−

µ

Beta ν−

e (He6)

Beta νe (Ne18)

CC Rates

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 0.2 0.4 0.6 0.8 1

Eν (GeV)ν

CC

/kto

n/y

ear

SPL νµ

SPL ν−

µ

Beta ν−

e (He6)

Beta νe (Ne18)

Fluxes @ 130 km < Eν > CC rate (no osc) < Eν > Years Integrated eventsν/m2/yr (GeV) events/kton/yr (GeV) (440 kton × 10 years)

SPL Super Beamνµ 4.78 · 1011 0.27 41.7 0.32 2 36698νµ 3.33 · 1011 0.25 6.6 0.30 8 23320

Beta Beamνe (γ = 60) 1.97 · 1011 0.24 4.5 0.28 10 19709νe (γ = 100) 1.88 · 1011 0.36 32.9 0.43 10 144783


Distinctive features of the Beta Beam

Just one neutrino flavour in the beam. No intrinsic contamination.

Short baseline: no subtraction of the fake CP violating matter effects.

Tunable: easy to adapt to the optimal ∆m223.

In the proposed scheme the νe channel is completely background free!

Neutrino fluxes are completely defined by the beta decay properties of the parent ion and by the

knowledge of the number of ions in the decay ring. This assures very small systematic errors and

a powerful measure of neutrino cross-sections in the close detector.

The νe and νe beams allow for the disappearance channel with a very good control of the systematics,

with a direct access to θ13 . Their comparison offers a tool to investigate CPT.

When combined with the νµ and νµ SPL beams, the νe and νe Beta Beams allow for CP, T, and

CPT searches.


Beta Beam Backgrounds

Computed with a full simulation and reconstruction program. (Nuance + Dave Casper).

π from NC interactions

The main source of background comes from pions

generated by resonant processes (∆++ production) in NC

interactions.

Pions cannot be separated from muons.

However the threshold for this process is 400 MeV.

Angular cuts have not be considered.

e/µ mis-identification

The full simulation shows that they can be kept well below

10−3 applying the following criteria:

• One ring event.

• Standard SuperK particle identification with likelihood

functions.

• A delayed decay electron.

Atmospheric neutrinos

Atmospheric neutrino background can be kept low only by

a very short duty cycle of the Beta Beam. A reduction

factor bigger than 103 is needed.

This is achieved by building 10 ns long Ion bunches.


Optimizing the Lorentz Boost γ (L=130 km): preferred values: γ = 55 ÷ 75

Higher γ produce more CC interactions

More collimated

neutrino production and higher cross sections.

γ

CC

Rat

e (a

.u.)

2.5

5

7.5

10

12.5

15

17.5

20

60 80 100 120 140

Background rate rises much faster than CC

interactions

From resonant pion production in νe NC interactions

ν flux must match the CP-odd oscillating term

Eν (GeV)

a.u

.

0

0.2

0.4

0.6

0.8

1

1.2

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Detection efficiency as function of ν energy

100 150 200 250 300 350 4000

0.2

0.4

0.6

0.8

1.0

Eff

icie

ncy

Neutrino Energy (MeV)

Std. Particle ID

+ decay electron


The SuperBeam - BetaBeam synergy: θ13 sensitivity

Computed for 5 years running, no signal in the experiment.

• No way to disentangle θ13 from δ in a high sensitivity experiment.

• The full information of experiment sensitivity is given by a bidimensional θ13 vs δ plot.

• Beta Beam can measure θ13 both in appearance and in disappearance mode. All theambiguities can be removed for θ13 ≥ 3.4

δCP

(deg.)

Sin

22

θ 13

CHOOZ excluded

CNGS combined

Beta Beam Disappearance (1% syst.)

BNL

J-Parc

SPL+Beta Beams

BetaBeam

SPL

10-4

10-3

10-2

10-1

-150 -100 -50 0 50 100 150

sin22θ

13

∆m2 2

3 (

eV

2)

SPL-SB

Beta Beam

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

x 10-2

10-3

10-2

10-1

Chooz excluded

J-Parc

0.5

%

1%

2%

CN

GS

Min

os

Assuming δ=0

Assuming ∆m = 2.5 10 223

−3eV

2


Beta Beam - Super Beam synergy: CP sensitivity

SUPER BEAM ONLY

-150

-100

-50

0

50

100

150

0 1 2 3 4 5 6 7 8

θ13

δ

θ13

δ

θ13

δ

θ13

δ

SUPER BEAM + BETA BEAM

-150

-100

-50

0

50

100

150

0 1 2 3 4 5 6 7 8

θ13

δ

θ13

δ

θ13

δ

θ13

δ

δm212 = 7 · 10−5 eV 2, θ13 = 3, δCP = π/2,

sign(∆m2) = +1

Beta Beam SPL-SB

6He 18Ne νµ νµ

(γ = 60) (γ = 100) (2 yrs) (8 yrs)

CC events (no osc, no cut) 19710 144784 36698 23320

Oscillated at the Chooz limit 612 5130 1279 774

Oscillated 44 529 93 82

δ oscillated -9 57 -20 12

Beam background 0 0 140 101

Detector backgrounds 1 397 37 50

δ-oscillated events indicates the difference between the oscillated events

computed with δ = 90 and with δ = 0.


A comparison of CP sensitivities: Beta Beam vs. Nufact

CP sensitivity, defined as the

capacity to separate at 99%CL max

CP (δ = π/2) from no CP (δ = 0).

Nufact sensitivity as computed in J.

Burguet-Castell et al., Nucl. Phys. B

608 (2001) 301:

• 50 GeV/c µ.

• 2 · 1020 useful µ decays/year.

• 5+5 years.

• 2 iron magnetized detectors, 40

kton, at 3000 and 7000 km.

• Full detector simulation, including

backgrounds and systematics.0

0.5

1

10-4

10-3

10-2

sin2θ13

∆m122

(x10

-4)

eV2

JParc sensitivity

Best LMA after SNO Salt

Nufact

BetaBeam

SPL SB

SPL+Beta

SB+BB, 1Mton

1

1 2

2

3

34

45

5


δ sensitivity: Nufact vs SPL SuperBeam + Beta Beam.

Minimum value of δ at 3σ from zero as function of θ13 . ∆m212 = 7 · 10−3 eV2.

JParc as computed by T. Kobayashi, J.Phys.G29:1493(2003)

Nufact curve is silver+gold, preliminary, courtesy of O. Mena. Its extension below 2 is under investigation.

0

20

40

60

80

10-4

10-3

10-2

sin2θ13

δ (d

eg.)

SB + BB, 440 kton

Nufact, gold+silverJparc phase II


Is the γHE = 60, γNE = 100 the absolute optimal configuration?Suggestion of P. Hernandez and J.J. Gomez-Cadenas

• The present SPS configuration allows max. 139 GeV/u. In this scenario the γHE = 60 − γNE = 100, baseline=130

km is the optimal configuration.

• Relaxing the SPS constrain and allowing for higher energies:

– The resonant NC single pion productions cross section saturates.

– The signal/background ratio starts to be favorable again.

• As for the neutrino factories the number of events per kton/year increases as Eν when computed at the optimal

baseline. In this energy range is even more favorable because below 1 GeV neutrino cross sections raise faster that

E+1ν .

• At higher energies it is possible to bin the events in energy bins.

The γHE = 360, γNE = 600 configuration, baseline=732 km, is still comfortable as far as concerns energy

reconstruction in a water Cerenkov detector and would have a ∼ 10 increase in CC rates.

This would require something like a SPS to Tevatron upgrade (that means replace all the magnets with a 2-3 years stop of

operations) or the usage of LHC as a third stage accelerator.

The fluxes in these configurations are not yet been studied.

M. Mezzetto, “Beta Beam”, NOVE 03, Venezia, 3-5 December 2003 18

Comment on BB cost estimatesEducated guess on possible costs USD/CHF 1.60UNO 960 MCHFSUPERBEAM LINE 100 MCHFSPL 300 MCHFPS UPGR. 100 MCHFSOURCE (EURISOL), STORAGE RING 100 MCHFSPS 5 MCHFDECAY RING CIVIL ENG. 400 MCHFDECAY RING OPTICS 100 MCHF

TOTAL (MCHF) 2065 MCHFTOTAL (MUSD) 1291 MUSD

INCREMENTAL COST (MCHF) 705 MCHFINCREMENTAL COST (MUSD) 441 MUSD

A. Jansson, Rencontres de Moriond 2003

Estimated losses–CERN scenario6He

18Ne

Machine Ions extracted Batches Loss power Power/lengthSource+Cyclotron 2 e6 /s 52.5 msStorage ring 1.0 e12 1 3.0 W 19 mW/mFast cycling syncrotron 1.0 e12 16 7.4 W 47 mW/mPS 1.0 e13 1 765 W 1.2 W/mSPS 0.9 e13 inf 3.63 kW 0.41 W/mDecay ring 2.0 e14 * 157 kW 8.9 W/m

Machine Ions extracted Batches Loss power Power/lengthSource+Cyclotron 8 e11 /s 52.5 msStorage ring 4.1e10 1 0.18 W 1.1 mW/mFast cycling syncrotron 4.1 e10 16 0.46 W 2.9 mW/mPS 5.2 e11 1 56.4 W 90 mW/mSPS 5.9 e11 inf 277 W 32 mW/mDecay ring 9.1 e12 * 10.6 W 0.6 W/m

These numbers assumes 8s rep rate and only include decay losses from the beta beam!

(lost on inside)

(lost on outside)

limit

* denotes equilibrium intensity in decay ring

Introducing Neutrino Factories

• The dream beam of every neutrino physicist.

• The first case in which the whole neutrino production chain,

including proton acceleration, is accounted on the budget of

the neutrino beam construction.

• Beam intensities predicted to be two orders of magnitude

higher than in traditional neutrino beams.

• No hadronic MonteCarlos to predict neutrino fluxes.

• Oscillated events Nosc at a distance L:

Nosc ∼ Flux × σν × Posc ∼ E3ν

L2sin2 L

Eν

∝ Eν

Nosc increases linearly with the beam energy. Optimal energy:

as high as possible.

• Neutrino beams from muon decays contain ONLY two types of

neutrinos of opposite helicities (νe νµ or νe νµ ). It is possible

to search for νµ → νe transitions characterized by the

appearance of WRONG SIGN MUONS, without intrinsic

beam backgrounds.

0.2 0.4 0.6 0.8 1

Polarization= +1

P= -1

P= 0

P= +0.3

P= −0.3

0.2 0.4 0.6 0.8 1

P= -1P= −0.3

P= +0.3

νµ

νe

Eν/EµN

umbe

r of

cha

rged

cur

rent

inte

ract

ions

_


The basic concept of a neutrino factory (the CERN scheme)

• High power (4 MW) proton beam onto a liquid

mercury target.

• System for collection of the produced pions

and their decay products, the muons.

• Energy spread and transverse emittance

have to be reduced: “phase rotation” and

ionization cooling

• Acceleration of the muon beam with a LINAC

and Recirculating Linear Accelerators.

• Muons are injected into a storage ring (decay

ring), where they decay in long straight

sections in order to deliver the desired

neutrino beams.

• GOAL: ≥ 1020 µ decays per straight

section per year


Alain Blondel, Venice, March 2003

Detector

Iron calorimeterMagnetized

Charge discriminationB = 1 T

R = 10 m, L = 20 mFiducial mass = 40 kT

Baseline

3500 Km732 Km 3.5 x 107

1.2 x 106

5.9 x 107

2.4 x 106

1.1 x 105

1.0 x 105

CC νe CC signal (sin2θ13=0.01)

Events for 1 year

Also: L Arg detector: magnetized ICARUSWrong sign muons, electrons, taus and NC evts

(cf 40 in JHF-SK)

νµ


Can genuine CP effects be separated from matter effects?

Genuine CP-odd, δ driven effects can be

decoupled from matter effects, but paying a

high price:

1. The experiment must be run at a baseline

shorter than the optimal one.

2. A strong correlation between δ and θ13 .

3. The experimental result is affected by the

incertitude on the other parameters of the

mixing matrix and by the incertitude on the

matter density along the beam line.

From V. Barger et al., hep-ph/0003184.

Matter Effect

CP violationStat errors for10 decays21

Baseline (Km)

2000 4000 6000 8000

1

10

100

0.1

0.01

∆m >0232

∆m <0232


Simultaneous fits at δ e θ13 (from Nucl.Phys. B608(2001)301)

L = 732 Km

6 7 8 9 10

−150

−100

−50

0

50

100

150

*

*

*

*

*

θ13

δ

L = 2810 Km

2 4 6 8 10

−150

−100

−50

0

50

100

150

**

**

**

*

*

*

*

13

δ

L = 7332 Km

2 4 6 8 10

−150

−100

−50

0

50

100

150

**

**

**

*

*

*

*

θ13

δ

*

*

*

*

*

*

*

*

*

*

*

*

*

*

θ

2 4 6 8 10

−150

−100

−50

0

50

100

150

Λ 7332

13θ

δ

L = 2810 Km + L = 7332 Km

*

*

*

*

*

*

*

*


The δ, θ13 degereracy is better cured by the silver channel .

• From D. Autiero et al., hep-ph/0305185

• νe → νµ and νe → ντ oscillations

have opposite sign dependence from the

δ term a

• This behavior better solves the δ-θ13

ambiguities.

• νe → ντ oscillations can be

detected by an Opera/Icarus like like

detectors.

• Computation for a detector twice as big

as Opera (4 kton), at 732 km from

Nufact (CERN-LNGS), coupled to a 40

kton iron magnetic detector at 2810 km

(Cern-Canary Islands).

aThat can easily derived considering that

p(νe → νe ) cannot violate CP (is T invariant),

being 1-p(νe → νe ) =p(νe → ντ ) +p(νe →νµ ) , the δ terms of the last two terms must cancel.

−3 −1.5 0 1.5 ∆θ

−180

−90

0

90

180

δ

732 Km3000 Km

0 1 2 313

180

90

0

90

180

∆

best fit point

"clone"

−3 −2 −1 0 1 2 ∆θ

−180

−90

0

90

180

δ

goldensilver

0 1 2 313

180

90

0

90

180

∆

best fit point


Precision measurements at the Neutrino Factories

Improve up to 4 orders

of magnitude the Chooz

sensitivity on θ13

5107 106 5106 105 5105

sin2θ13

0.001

0.002

0.003

0.004

0.005

0.006

m232

732 km7332 km

3000 km

∆

Measure the ∆m223 sign

Measure the atmospheric

parameters at 1%.


NO-VE MICE Alain Blondel, 4/12/03

Neutrino Factory studies and R&D

USA, Europe, Japan have each their scheme. Only one has been costed, US study II:

Neutrino Factory CAN be done…..but it is too expensive as is.Aim: ascertain challenges can be met + cut cost in half.

+ detector: MINOS * 10 = about 300 M€ or M$

Synergy and not competition

The cost and the time scale of the two

facilities are different.

Their approach is completely

complementary.

Super(Beta)Beams are needed to eliminate

any parameter degeneracy in case

θ13 < 2.

The synergy of the two approaches must be

used to reach the ultimate sensitivity to the

leptonic CP violation.

Plot taken from A. Donini, hep-ph0310014,

golden is a magnetic detector of 40 kton at

2810 km, silver is an emulsion detector of 4

kton at 732 km, SPL SB is the CERN SPL

SuperBeam fired to a 400 kton Cerenkov

detector at 130 Km.

-2 -1.5 -1 -0.5 0 2θ13

1.5 1 0.5

150

100

50

0

-50

-100

-150

δ NF Golden (2810)150

100

50

0

-50

-100

-150

δ

-2 -1.5 -1 -0.5 0 2θ13

1.5 1 0.5

NF Golden + SPL SB

150

100

50

0

-50

-100

-150

δ

-2 -1.5 -1 -0.5 0 2θ13

1.5 1 0.5

NF Golden + Silver NF Golden + Silver + SPL SB

150

100

50

0

-50

-100

-150δ

-2 -1.5 -1 -0.5 0 2θ13

1.5 1 0.5


Ongoing activities in Europe

APEC design study (sub 2005)

mNeutrino factoryThe ultimate tool for neutrino oscillations

Very large underground labWater Cerenkov, Liq.Arg

m/neutrino Factory design study (sub 2005)

SPL Superbea

Beta beamEURISOL

Superbea

EURISOL design study (sub 2004)

HIPPI

SPL physics workshop: 25-26 May 2004 at CERNCERN SPSC Cogne meeting sept. 2004


Conclusions

• The neutrino oscillation roadmap predicts several tens years to be completed in the simplest

scenario.

• Leptonic CP violation searches require accelerators, detectors and cooperation at scales unknown

to the neutrino physicists.

• A working group on physics at the future neutrino beams is active in Europe, sponsored by ECFA

and the novel EU network BENE. The conveners are [email protected] and

[email protected], the web page is http://axpd24.pd.infn.it/nowg


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