tsearch v1 6

Transcript

tsearch v1 6

Neutrino Oscillations

Neutrino oscillations depend from



νe
ν1




 νµ  = U  ν3 




ντ
ν3
• 3 mixing angles, θ12 , θ23 , θ13
• 2 mass differences: ∆m212 , ∆m223
• 1 CP phase δ

−iδ

c13 s12
s13 e
c13 c12


iδ
iδ

U (θ12 , θ23 , θ13 , δ) =  −c23 s12 − s13 s23 c12 e
c23 c12 − s13 s23 s12 e
c13 s23 

s23 s12 − s13 c23 c12 eiδ −s23 c12 − s13 c23 s12 eiδ c13 c13
In vacuum:
P (να → νβ ) = −4
2
jk
2 ∆mjk L
k>j Re[Wαβ ] sin
4Eν
±2
2
jk
2 ∆mjk L
k>j Im[Wαβ ] sin
2Eν
2 neutrinos : P (να → νβ ) = sin2 2θ · sin2 (1.27∆m2αβ [eV 2 ]L[km]/E[GeV ])
M. Mezzetto, Lezioni Dottorato di Ricerca, Padova, aprile 2003.
1
α = e, µ, τ
j = 1, 2, 3
jk
∗
∗
Wαβ
= Uαj Uβj
Uαk
Uβk
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.
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
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
SK
SCP
SST
Evidence for Oscillation of Atmospheric Neutrinos.
Measurements of Ω and Λ from 42 High Redshift SN.
Observational Evidence from SuperNovae for an
1705
1311
1293
COBE
CDF
D0
SK
Chooz
Boomerang
Chooz
Accelerating Universe and a Cosmological Constant.
Structure in the COBE DMR First Year Maps.
Observation of TOP Quark Production in p − p Collisions.
Observation of the Top Quark.
Atmospheric νµ /νe Ratio in the MultiGeV Energy Range.
Initial Results from CHOOZ.
A Flat Universe from High Resolution Maps of the CMB.
Limits on Neutrino Oscillations from the CHOOZ
1036
930
889
751
683
644
635
Kamiokande
CLEO
SNO
Homestake
LSND
SK
CDF
SK
IMB
SK
LSND
Experiment.
Observation of a Small Atmospheric νµ /νe Ratio.
First Measurement of the Rate for the Inclusive b —> sγ .
Measurement of the rate of νe + d –> p + p + e- ...
Measurement of the Solar νe Flux ...
Evidence for ν µ —> ν e Oscillations from LSND.
Measurement of a Small Atmospheric νµ /νe Ratio.
Evidence for TOP Quark Production in p − p ....
Study of the Atm. ν Flux in the MultiGeV Energy Range.
The νe and νµ Content of the Atmospheric Flux.
Solar Neutrino Data Covering Solar Cycle 22.
Neutrino Oscillations from LSND.
628
618
592
565
563
561
550
547
535
504
500
3
Most of the parameters are waiting to be measured
2
12
δm
θ12
SOLARS+KAMLAND
-4
-5
2
5 10 <δm12<3 10 eV
2
SOLARS+KAMLAND
2
0.2 < sin ( θ 12 ) < 0.5
Addressed by a SuperBeam/Nufact experiment
δm
2
23
δm
2
23
= 2.6 +/- 0.4 eV
θ 13
δCP
Σ mν
θ23
ATMOSPHERICS
2
ATMOSPHERICS
0.9 < sin 2( θ23 ) < 1
2
CHOOZ LIMIT
θ 13
< 14 0
Mass hierarchy
BETA DECAY END POINT
Σ m ν < 6.6 eV
Dirac/Majorana
4
Neutrino Oscillation Experiments
Palo Verde
Minos
LSND
Mini Boone
???? Numi off-axis ????
SNO
Kamland
K2K
JHF Fase I
Fase II (?)
Super Kamiokande
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
Chorus
Opera
Nomad
Icarus
2008
2009
2010
GNO
2012
2013
2014
2015
Nufact ?
Macro
Chooz
2011
Borex
5
The capital importance of θ13
Present limit from CHOOZ: sin2 2θ13
≤ 0.1. Both solar and atmospheric results are compatible with θ13 = 0.
Solar+Atmospherics favor a near bi-maximal mixing matrix (VERY DIFFERENT from CKM matrix!)


−iδ
0 s13 e
1
0
0
c13



U =
0
1
0
 0 c23 s23  
−s13 eiδ 0
0 −s23 c23
c13
θ13 → 0
⇒


c12 s12 0


  −s12 c12 0  ,


0
0 1
The 3x3 matrix is a trivial product of two 2x2 matrixes.
θ13 drives νµ → νe subleading transitions ⇒
the necessary milestone for any subsequent search:
neutrino mass hierarchy and leptonic CP searches.
6
Subleading νµ
p(νµνe)
<E >=1.00 GeV
2
sin (2θ 13)=0.01
sin2(2θ 12)=0.8
δm 213 =2.5E-3 eV 2
2
δm 12 =7.E-5 eV 2
δ=0
− νe oscillations
Solar peak
p(νµ → νe ) developed at the first order of matter effects
p(νµ → νe ) =
θ13 peak
0
5000
10000
15000
20000
25000
30000
p(νµνe)
L (km)
Total
Solar
θ13
CPeven
CPodd
0.008
0.007
0.006
0.005
δ =-π/2
JHF
equivalent
baseline
CNGS
equivalent
baseline
0.004
0.003
4c213 s213 s223
∆m213 L
sin
4E
2
θ13 driven
∆m213 L
∆m212 L
∆m223 L
+
sin
sin
CPeven
− s12 s13 s23 ) cos
4E
4E
4E
∆m213 L
∆m212 L
∆m223 L
2
− 8c13 c12 c23 s12 s13 s23 sin δ sin
sin
sin
CPodd
4E
4E
4E
∆m212 L
2 2
2 2
2 2 2
+ 4s12 c13 {c13 c23 + s12 s23 s13 − 2c12 c23 s12 s23 s13 cosδ} sin
solar driven
4E
∆m213 L aL
∆m223 L
− 8c212 s213 s223 cos
sin
(1 − 2s213 ) matter eﬀect (CP odd)
4E
4E 4E
√
where a = ±2 2GF ne Eν = 7.6 · 10−5 ρ[g/cm3 ]Eν [GeV ] [eV 2 ]
8c213 s12 s13 s23 (c12 c23 cosδ
0.002
0.001
0
0
50
100
150
200
250
300
350
400
450
500
L (km)
7
The hunting for θ13
• Possibilities of the next Long Baseline experiments.
• Possible experimental approaches.
• Proposals for new initiatives
8
Possible experimental approaches to θ13 , Part I
Long Baseline Experiments
Detect νµ
→ νe transitions via νe appearance in a
not so pure νµ beam.
Experimental backgrounds:
• Beam νe contamination (∼ 0.5%)
• π ◦ production in NC νµ interactions.
• νµ → ντ → τ → e− ν e ντ
(N.B. ντ production ∝ (∆m223 )2 , very difficult
to normalize in absence of a precise measure
of ∆m223 )
MINOS
Twice the Chooz sensitivity, limited by the coarse
granularity of the detector and by the systematics.
ICARUS
Five times the Chooz sensitivity in 8 years of data
Upgrade CHOOZ
(Mikaelyan et al.
hep-ph/0109277,
D. Nicoló at NO-VE 2001)
The cleanest approach to θ13 is
2
p(νe → νe ) ∝ 1 − sin
not influenced by δ or MSW effects.
Chooz can be improved by a factor 5 if:
• Use a detector as big as 10× the Chooz detector.
• Use a close detector, to be placed underground ⇒
σsys 0.5%
• Measure backgrounds at reactor off ⇒
σstat 0.5%
taking with a 3 kton detector. Computed neglecting
systematic errors (but no close detector in the
CNGS beam).
2
2 ∆matm L
2θ13 sin
,
4E
9
Possible experimental approaches to θ13 , Part II
Atmospheric Neutrino MSW resonance in the Earth
(Bernabeu et al.
hep-ph/0102184, Monolith internal
SuperNovae
notes)
The resonance is described by
• ER = ± cos 2θ13 2
• ΓR =
∆m2
√ 13
2GF Ne
∆m2
2 sin 2θ13 2√2G 13N .
F e
This latter can measure
a good
θ13 , having a detector with
L/E resolution, as for instance Monolith.
neutrinos
MSW
in
the
Earth
(Smirnov-Lunardini. hep-ph/01006149)
Three big Supernovae detectors are running: SK, SNO,
LVD in three different contintents.
In case of a galactic (∼
10 Mpc) SuperNova explosion,
it’s very likely that one detector can measure the
1.4
SN neutrino spectrum undistorted, while another can
1.2
measure the ν after they have crossed the Earth’s Core.
1
The first one normalizes the spectrum, the second
0.8
can directly measure the MSW distortion to the
0.6
spectrum.
0.4
Model independent measurement of sign(∆m212 ) at 2-3
0.2
0
10
2
10
3
L/E (km/GeV)
σ and a verification that sin2 2θ13 ≥ 10−5 (otherwhile
the transition cannot happen).
200 kton/year ⇒ 2× Chooz
400 kton/year ⇒ 4× Chooz (scales with sin 2θ13 )
10
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).
NCC (/100MeV/22.5kt/yr)
400
Energy of the max. of oscillation
according to SK 90% allowed region
350
Off Axis 1 degree
300
0
OA 2 250
200
K2K
6 · 1012
JHF
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
Wide Band Beam
150
100
OA 30
50
0
0
1
11
2
3
4
5
E (GeV)
Off Axis Neutrino Beams. BNL-E889 proposal: http://minos.phy.bnl.gov/nwg/papers/E889
Decay Kinematics
ν(Εν)
A qualitative argument:
0.06
θ
π (mπ,pπ)
• Transverse
momentum,
0.03
(GeV/c)
µ (mµ,pµ)
From momentum energy conservation:
m2π − m2µ
Eν =
2(Eπ − pπ cosθ)
invariant:
momentum is Lorentz
boosted.
-0.03
• At
an angle θ there is an
0
1
2
3
(GeV/c)
θ = 0 mrad
θ = 7 mrad
θ = 14 mrad
θ = 27 mrad
mπ − mµ .
• Longitudinal
0
-0.06
15
Lorentz
accumulation of lower
energies neutrinos
Eν (GeV)
• Maximum neutrino flux at 0◦ .
• Off axis is the most efficient way to have a narrow band
10
beam.
• νe come from 3 body decays (kaons or muons) while
off-axis is optimized on the pion 2 body decay⇒ the
νe contamination below the peak is reduced.
5
0
0
10
20
Eπ (GeV)
30
40
12
JHF (continued)
Precision measure of the atmospheric parameters:
• δm223 with a resolution of 10−4 eV2 .
• sin2 2θ23 at 1 ÷ 2 %.
Sensitivity to θ13
90% C.L. sensitivities
-1
∆m2(eV2)
10
1
-2
10
x20
10
-1
-3
10
0
1000
2000
3000
JHF 5years
WBB
OAB 2deg.
NBB 2GeV
CHOOZ excluded
E (MeV)
ν
Ratio of the measured
νµ spectrum with respect to the
-4
10
10
-3
10
-2
non-oscillation prediction in case of oscillation (5 years).
13
10
-1
sin22θµe
1
δ m2 = 3 × 10
5 ears
1)
2)
3)
4)
2
enerated in F
1 e li e
0
e π0
se aration
0 4 e E ec
45
40
35
30
25
20
15
10
5
0
1.2
e
3
e
2
and sin2 2θ0
µe = 0.05
νµ C C ν µ C
10713 6 4080 3
14 3
247 1
35
23 0
18
93
eam νe
292 1
68 4
21 9
11 1
scillated νe
301 6
203 7
152 2
123 2
Expected Signal+BG
Total BG
BG from νµ
0
1
2
3
4
5
Reconstructed Eν(GeV)
80
70
60
50
40
30
20
10
0
20
17.5
15
12.5
10
7.5
5
2.5
0
0∝
0
0.5
0e
0
0.5
1
60
50
40
30
20
10
0
cos00e
1
cos00e
90
80
70
60
50
40
30
20
10
0
0∝
0
100
200
8
7
6
5
4
3
2
1
0
-500
200
25
20
15
10
5
0
-500
inv. mass (MeV)
100
0
0∝
500
14
12
10
8
6
4
2
0
likelihood difference
0e
0
0∝
0
0e
inv. mass (MeV)
0
0.25
0.5
E(02)/(E(01)+E(02))
0e
500
likelihood difference
25
20
15
10
5
0
0
0.25
0.5
E(02)/(E(01)+E(02))
o t e an tities sed in t e e/ 0 separation
e eam is t e o
2 de ree eam and
events are a ter t e sin le rin e li e selection pper isto rams corresponds to µ ac ro andis events and t e lo er
isto rams correspond to t e e si nal events
e arro s in t e
re s o t e c t positions sed in t e anal sis
Fi ure 9: istri tions
14
Separazione ντ
− νsterili
Tag
delle
correnti
◦
neutre con i π (metodo Vissani-Smirnov), usato anche
in SK (ν
+ N → ν + N + π◦ )
π 0+ e-like events
1000
900
ν µν τ
800
700
600
Le sistematiche sulla sezione d’urto di produzione
◦
500
π in eventi di NC verranno fortemente
400
ridotte dal close detector di K2K e dai close detectors
300
di JHF.
200
risonante di
Limite alla frazione di νs a circa 0.1 (90% CL).
ν µν s
100
0
10
390 +/− 44
-4
10
-3
15
10
-2
∆m
2
10
-1
What about Numi and CNGS off-axis?
CNGS off-axis (Dydak’s talk at Neutrino 2002)
NuMi off-axis (LoI of 05/06/2002)
• Use NuMi Medium Energy beam
• Place a detector at ∼ 730 km, 9 km off-axis (0.7◦ ),
that means NOT deep underground.
• The far detector is not yet well specified however it
should be:
– 20 kton, fiducial = 85% of total.
– Good
π◦ rejection in the 1-3 GeV energy range
(π ◦ bacground must be reduced below the level
of beam νe contamination)
– Cost below 100 M$
– Ready in 2008 (the JHF clock!)
Under these conditions it could have a θ13 sensitivity
similar to JHF.
• Modify the CNGS in order to have a mean energy
of 3.5 GeV (renouncing to any tau appearance
experiment at LNGS or waiting for 2011).
• Place a detector underwater, off-axis, in the Gulf
of Taranto, in TWO positions corresponding to the
SECOND oscillation maximum and minimum.
• The detector should be made by 4000 PMTS, in a
grid of 6m side, equipping a cone of 1 Mton of water
(radius 110m, height 25 m).
• With a coverage of 2% of the surface (SK has 40%)
it should reduce the π◦ background to less than 1%
of the νµCC (SK has 2.5% of π◦ with not optimized
algorithms).
• It should cost 100 M$ (???)
• It should be ready in 2008 to compete with JHF
16
Leptonic CP
Two conditions to make Leptonic CP detectable:
• Solar LMA confirmed
• θ13 ≥ 0.50 (see the following).
A big step from a θ13 search:

 p(ν → ν ) =
p(ν µ → ν e ) (direct CP)
µ
e
from p(νµ → νe ) =
0 to
 p(νµ → νe ) =
p(νe → νµ ) (T search)
This will require:
Super Beams
1. Neutrino beams of novel conception.
Neutrino Factory
Beta Beams
2. Detectors of unprecedent mass
3. Improved control of systematics
⇒ Dedicated experiments on neutrino cross-section, hadron
production, particle ID.
17
Detecting the δ phase at the Neutrino Factories
AÆ = [P (ν → ν , δ = +π/2) − P (ν → ν , 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.
A (δ) = [P (ν → ν , δ) − P (ν → ν , δ)]/[P (ν → ν , δ) + P (ν → ν , δ)]
Compare the appearance of νµ (ν µ ) 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.
A (δ) = [P (ν → ν , δ) − P (ν → ν , δ)]/[P (ν → ν , δ) + P (ν → ν , 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.
18
Are CP-odd effects detectable?
ACP
sin 2θ12
P (ν e → ν µ ) − P (νe → νµ )
∆m212 L
=
· sin δ · sin
P (ν e → ν µ ) + P (νe → νµ )
sin θ13
4E
ACP vanishes in the limit ∆m212 → 0
ACP ∝ sin 2θ12
Only the solar LMA solution allows a detectable ∆CP
Latest SNO results are very much in favor of LMA, but the final
worlds will come from the Kamland experiment, that’s running.
LSND scenario: CP violation arises from interference between:
• LSND frequency ∼ 0.3 to 2 eV 2 .
• Atmospheric frequency ∼ 3 · 10−3 eV 2 .
Amplitudes comparable at atmospheric baseline
Near 100% CP asymmetry is possible
19
The delightful news from solar neutrino experiments
2 YEARS AGO
NOW, AFTER SNO and KAMLAND
2
δm12
2
δm12
LMA - II
LMA
LMA - I
Preferred by
CP searches
LOW
QUAS I
VACUUM
maxima l mixing line
maxima l mixing line
2
2
tan θ12
sin θ12
20
δ and θ13 interplay.
P (ν → ν ) ∝ sin2 2θ13
A ∝
1
sin 13
⇓
sin2 2θ13 ≤ 10−3
⇒ practically impossible to detect CP
through νµ → νe transitions (see later).
P (ν → ν ) ∝ sin2
To detect
νµ
∆2
23 4
→ νe transitions with high
sensitivity are needed:
sin2 2θ13 small ⇒ small statistics but big asymmetry.
sin2 2θ13 big ⇒ high statistics but small asymmetry
⇓
Very clean neutrino beams.
Very intense neutrino beams:
The
CNGS
beam
The two effects tend to balance BUT detector requirements are
intensity is about two orders of magnitude
very different in the two cases: high mass and reduced resolution
smaller to what needed to run a CP search at
against ”small” mass but high resolution.
the appropriate baseline (∼
8000 km) with
enough statistics in a 50 kton detector.
Very risky to start a CP search without knowing the real value of
θ13 , certainly without knowing that sin2 2θ13 ≥ 10−3
21
δ and θ13 interplay (II).
On the other hand any θ13 experiment not sensitive to CP can see the effect but cannot precisely measure θ13 .
p(νe → νµ ) in the case of the JHF experiment, from
hep-ex/0106019
Contributes to
10
JHF
2
295 km
10% syst. on backgrounds
δ uncertitude
δ m231 eV2
mass hyerarchy
uncertitude
10
3
10
22
3
10 2
sin2 2θ
2 13
10
1
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
• Oscillated events Nosc at a distance L:
Nosc ∼ Flux × σν × Posc ∼
Eν3
L2
sin2
L
∝ Eν
Eν
Nosc increases linearly with the beam energy. Optimal energy:
as high as possible.
• Beam intensities predicted to be two orders of magnitude
higher than in traditional neutrino beams.
• No hadronic MonteCarlos to predict neutrino fluxes.
• Neutrino beams from muon decays contain ONLY two types of
neutrinos of opposite helicities (ν e νµ or νe ν µ ). It is possible
to search for νµ → νe transitions characterized by the
Number of charged current interactions
the neutrino beam construction.
_
νµ
P= +0.3
P= 0
P= −0.3
P= -1
0.2
0.4
νe
0.6
0.8
1
P= -1
P= −0.3
P= +0.3
0.2
0.4
0.6
Eν/Eµ
appearance of WRONG SIGN MUONS, without intrinsic
beam backgrounds.
Polarization= +1
23
0.8
1
Why a Neutrino Factory is far more efficient of a conventional neutrino beam
BCT1
Al Collimator
SEMs
BCT2
Reflector
Horn
CHORUS
Muon Pits
Decay
Earth
Tunnel
Be Target
450 GeV/c protons
TDX collimator
Iron Shield
NOMAD
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 · 10−8 s), 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.
Hard to predict the details of the neutrino beam, since it derives from hadronic interactions. At least four neutrino flavours
are present (νµ , ν µ , νe , ν e )
In a neutrino factory pions decay inside a solenoid, and most of the muons are collected. Muons are longeval enough
(2.2 · 10−6 s) to open the possibility to collimate and accelerate them to the desired momentum.
Much more efficient way to produce neutrinos BUT a real challenge to accelerate, in a very short time, particles generated
with a large emittance .
Two possible solutions,
• Ionization cooling (stochastic cooling is too slow).
• Very large aperture accelerators (FFAG)
R&D.
No need of hadronic MC to predict the fluxes and only
two ν flavours in the beam
Both solutions have never been implemented and require
24
25
26
27
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
28
29
30
Detector
Iron calorimeter
Magnetized
Charge discrimination
B=1T
R = 10 m, L = 20 m
Fiducial mass = 40 kT
Also: L Arg detector: magnetized ICARUS
Wrong sign muons, electrons, taus and NC evts
Baseline
732 Km
3500 Km
Events for 1 year
CC
e CC
3.5 x 107 5.9 x 107
1.2 x 106 2.4 x 106
signal (sin2
1.1 x 105
1.0 x 105
13=0.01)
(cf 40 in JHF-SK)
Alain Blondel, Venice, March 2003 M. Mezzetto, Lezioni Dottorato di Ricerca, Padova, aprile 2003.
31
Possible detectors 2): Liquid Argon TPC
• The first 300 ton module is operational.
• Excellent energy resolution, tracking, particle
identification.
• Difficult to scale to a multi-10kton detector.
• Non trivial implementation of magnetic field:
downstream spectrometers.
The possibility to
magnetize large, multikiloton volume of Argon is
under study.
• Conceptual possibility to measure the charge of
electrons if the full volume is magnetized at 1 Tesla.
• The best solution if redundant searches of
oscillations are needed to overconstrain the mixing
matrix.
32
UNO detector
• Fiducial volume: 440 kton: 20 times SuperK.
• The
killer detector for proton decay, atmospheric
neutrinos, supernovae neutrinos.
• Energy resolution is poor for multitrack
events but quite adequate for sub-GeV
neutrino interactions.
• Difficult implementation of magnetic field:
downstream spectrometers.
33
A problem ...
Oscillated events Nosc at a distance L:
Nosc ∼ Flux × σν × Posc
Eν3 2 L
∼ 2 sin
∝ Eν
L
Eν
Nosc increases linearly with the beam energy. ⇒ Optimal energy: as high as possible.
⇓
High Neutrino Energies ⇒ Long Baselines ⇒ Matter Effects
34
Can genuine CP effects be separated from matter effects?
From
Genuine CP-odd,
V.
Barger
et
al.,
hep-ph/0003184.
δ driven effects can be
decoupled from matter effects, but paying a
high price:
100
10
2
∆m32<0
1. The experiment must be run at a baseline
much shorter than the optimal one.
2. A strong correlation between δ and θ13 .
3. The experimental result is affected by the
uncertitude on the other parameters of the
1
Matter Effect
0.1
0.01
2
∆m32 >0
CP violation
Stat errors for
21
10 decays
mixing matrix and by the uncertitude on the
matter density along the beam line.
2000
4000
6000
8000
Baseline (Km)
35
Simultaneous fits at δ e θ13 (from Nucl.Phys. B608(2001)301)
L = 2810 Km
L = 732 Km
δ
**
150
*
*
**
*
**
*
**
*
150
δ
100
100
**
50
50
0
0
*
−50
−50
**
−100
−100
−150
−150
*
*
2
7
6
8
9
θ13
L = 7332 Km
*
**
**
10
θ 13
100
*
*
50
50
**
0
**
*
Λ
7332
*
−50
−50
−100
*
8
δ 150
δ
0
6
L = 2810 Km + L = 7332 Km
*
150
100
4
10
**
**
−100
−150
*
*
−150
*
*
2
4
6
**8
10
*2
4
*8
10
θ 13
θ13
6
36
37
Precision measurements at the Neutrino Factories
Measure the atmospheric
Improve up to 4 orders
of magnitude the Chooz
Measure the
sensitivity on θ13
∆m223
parameters at 1%.
sign
0.006
0.005
7332 km
732 km
3000 km
0.004
∆ m223
0.003
0.002
0.001
5 10
7
10
6
5 10 6 10
sin2θ13
5
5 10
5
38
Final Sensitivity
• Matter effects must be separated from genuine
kton large magnetic detector (full simulation, full
99%CL max CP (δ
= π/2) from no CP (δ = 0)
computed as function of the two critical parameters
θ13 and δm212
1
21
2
• Strong correlations in the simultaneus fit of θ13 and
δ.
• The errors of all the other mixing matrix parameters
influence the precision of the measure of δ . On the
other hand a ν F can measure θ23 e ∆m223 at 1%
through the νµ disappearance.
• Backgrounds ed efficiencies computed for a 40
CP sensitivity, defined as the capacity to separate at
Nufact, 10
∆m122(x10 -4 ) eV
CP-odd effects.
0.8
0.6
Icarus, 732 km, 10 kton, 10
reconstruction).
• (J. Burguet-Castell et al., Nucl. Phys. B 608 (2001)
µ decays, L=2810+7332
21
µ decays, 90 % CL
0.4
301 )
0.2
Two detectors at two different baselines are the
0
0
1
2
4
5
6
7
θ13(degree)
optimal solution for the Leptonic CP detection. Best
combination: 3000+7000 km.
3
39
8
SuperBeams (1) - JHF phase 2
Upgrade the proton driver from 0.75 MW to 4 MW
Upgrade SuperKamiokande by a factor 40 =⇒ HyperKamiokande
40
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 νµ

e+ νe ν µ
they can be predicted from
large detectors are necessary in
νµ CC
spite of the very intense neutrino
the
+
⇒
Less exiting aspects of a low
energy neutrino beam
• Cross sections are small ⇒
measured
spectrum both at the close
and at the far detector with
beam.
• ν µ production is disfavored for
two reasons:
a small systematic error of
– Smaller
∼ 2%.
Detector Backgrounds
• Good e/π 0 separation following the large π0 → γγ opening angle
• Good e/µ separation in a Čerenkov detector because µ are produced
below or just above the Čerenkov threshold.
target.
–
ν µ /νµ cross section ratio is
at a minimum (1/5).
• Visible energy is smeared out by
Fermi motion
• Charm and τ production below threshold.
π− multiplicity at the
41
A feasibility study of the CERN possible developments
20 m
ν/100 m2/20 MeV
SPL-SuperBeam at CERN
ν
10
13
10
12
10
11
10
10
Flux Eν(GeV)
νe 2.16E+12 0.32 0.668
νµ 5.16E+12 0.28 1.598
νe 1.24E+10 0.29 0.004
10
9
10
8
10
7
10
6
Decay Tunnel
Near Detector
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
ν
intensities
1
at
50
km
from
the
target
Absolute Flux
Rel. Flux
E ν (ν/1023 pot/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
Flavour
Far Detector
Possible Low Energy Super Beam Layout
0.9
Eν(GeV)
Flux
km
130
(%)
νµ 3.23E+14 0.27
42
MW-Linac: SPL (Superconducting Proton Linac)
45 keV 7 MeV 120 MeV 1.08 GeV 2.2 GeV
13m
3 MeV
78m
18MeV 334m
345m
237MeV 389MeV
- RFQ1 chop. RFQ2 DTL
CCDTL
RFQ1 chop.
RFQ2 RFQ1 chop. RFQ2
β 0.52 β 0.7 β 0.8 LEP-II
H
Source Low Energy section
DTL
Re-use superconducting
LEP cavities
cavities
dump
Superconducting section
Stretching and
collimation line
PS / Isolde
Accumulator Ring
EKIN = 2.2 GeV
Power = 4 MW
Protons/s = 10 16
23
10 protons/year
43
UNO detector
• Fiducial volume: 440 kton: 20 times SuperK.
• 60000 PMTs (20”) in the inner detector,
15000 PMTs in the outer veto detector.
• The
killer
detector
for proton decay, atmospheric neutrinos,
supernovae neutrinos.
• 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.
• Quoted at 500M$ (including excavation)
44
2
δ and θ13 interplay: P (νµ → νe ) ∝ sin 2θ13
ACP =
P( νµ - νe ) x 10
∝
P( νµ - νe )
0.04
P(ν µ -ν e)
P(ν µ -ν e)
N (e+ )−N (e− )
N (e+ )+N (e− )
0.03
0.04
0.03
0.02
0.02
0.01
0.01
0
0
-0.01
-0.01
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0
1
0.1
0.2
0.3
0.4
0.5
δ
150
100
50
0
-50
-100
-150
1
0.7
0.8
0.9
1
Eν (GeV)
Eν (GeV)
0
0.6
2
3
4
5
6
7
45
8
θ 13
1
sin θ13
δ
150
Sensitivity depends also by ∆m 212
-4 2
2
∆m = 1.5 10 eV
12
100
P( νµ - νe )
P(ν µ -ν e)
50
0
-50
0.025
0.02
-100
0.015
-150
0.01
δ
0.005
150
-4
2
∆m = 0.7 10 eV
12
100
0
2
-0.005
50
-0.01
0
0
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.5
0.6
0.7
0.8
P( νµ - νe )
-50
P(ν µ -ν e)
-100
-150
δ
0.1
0.9
1
0.9
1
Eν (GeV)
0.012
0.01
0.008
150
-4
2
100
∆m = 0.2 10 eV
12
2
0.006
50
0.004
0
0.002
-50
0
-100
0
-150
0
1
2
3
4
5
6
7
0.1
0.2
0.3
0.4
8
θ13
46
Eν (GeV)
(solars)
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).
The limiting factors for the SuperBeam at small
Nufact and SPL-SuperBeam sensitivities computed with the same
∆m122(x10-4) eV2
conditions.
θ13 values are:
• The low flux of ν and their small cross
section. This limits the overall statistic.
Nufact
• The beam related backgrounds that increase
SuperBeam
the statistical errors, hiding the CP signal.
1
θ13 =3◦ , δm212
0.7 · 10−4 eV 2 , sin2 2θ12 = 0.8:
As
Best LMA, hep-ph/0212127
an
example
for
0.5
µCC (no osc)
0
0
1
2
3
4
5
6
7
8
θ 13 (degrees)
Oscillated events (total)
Oscillated events (cp-odd)
Intrinsic beam background
Detector backgrounds
47
=
νµ beam
ν µ beam
2 years
36698
45
-84
140
36
8 years
23320
133
53
101
49
SuperBeam vs. Nufact
PROS
• Negligible matter effects: it can be run at the optimal baseline
• Negligible matter effects: reduced correlations between θ13 and δ
• Counting experiment: less influenced by uncertitudes on the other mixing
matrix parameters
CONS
• Smaller CC rate
• Intrinsic beam contamination
48
Can the SuperBeam+UNO combination be upgraded?
YES
with a novel concept of neutrino beam: BETA BEAM.
(P. Zucchelli: Phys. Lett. B532:166, 2002)
49
Beta Beam (P. Zucchelli: Phys. Lett. B532:166, 2002)
Muons are not the only unstable particles that decay
into neutrinos, there are also β emitter nuclei.
As for the neutrino factory the neutrino spectrum is
completely defined by the parent decay properties and
by the Lorentz boost γ .
To produce a Beta Beam:
β radioactive ions with a lifetime of the
order of ∼ 1s. Best candidate: 6 He, β − emitter
(E0 3.5 M eV , T /2 0.8 s).
1. Produce
2. Accelerate them to high energies in a conventional
way (PS).
3. Accumulate them in a decay ring with long straight
sections (SPS like).
4. Just ONE neutrino flavour is produced:
ν or ν .
CERN ISOLDE, if injected by SPL, could produce
7 · 1013 6 He/s by using 1/8 of the SPL duty cycle.
PS + SPS (modified to have 2.5 km long straight
sections). Today they are already accelerating heavy
ions up to γ
= 150.
The complexity of the FAST muon acceleration is absent
(simply 4 × 105 more time).
It is technologically feasible to build neutrino beams with
intensities comparable with SuperBeams.
CERN is the only place with the complete Beta Beam
know-how:
• Isotopes production (ISOLDE)
• Ion acceleration (PS+SPS+LHC)
• Neutrino Experiments (EP)
50
A Beta Beam sketch
M. Lindroos and collaborators, see http://beta-beam.web.ch/beta-beam
SPL
ISOL target
& Ion source
Decay
Ring
SPS
Cyclotrons
Storage ring and fast cycling
synchrotron
PS
• 1 ISOL target to produce HE6 , 100 µA, ⇒ 2.9 · 1018 ion decays/straight session/year. Source of νe .
• 3 ISOL targets to produce Ne18 , 100 µA, ⇒ 1.1 · 1018 ion decays/straight session/year. Source of νe .
• The 4 targets could run in parallel.
51
Optimizing the Lorentz Boost γ (L=130 km): preferred value:
γ = 75
Background rate rises much faster than CC
More collimated neutrino production and higher cross
interactions
sections.
20
From resonant pion production in
17.5
15
12.5
10
7.5
5
2.5
60
80
100
120
140
γ
1.2
1
1000
800
600
400
200
0
50
60
70
80
90 100 110 120 130 140 150
γ
Detection efficiency as function of ν energy
Efficiency
ν flux must match the CP-odd oscillating term
a.u.
νe NC interactions
1200
π+ in 4400 kton yr at 130 km
CC Rate (a.u.)
Higher γ produce more CC interactions
1.0
Std. Particle ID
0.8
+ decay electron
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7 0.8
Eν (GeV)
100
150
200
52
250
400
350
300
Neutrino Energy (MeV)
The SuperBeam - BetaBeam synergy
Run two neutrino beams to the same detector at the same time.
Both beams need SPL, but the BetaBeam requires at most 12% of the SPL
protons → the two beams can run together.
Both beams produce sub-GeV neutrinos
→ same baseline and same
detector.
CP, T and CPT searches at the same time !!!!
53
The SuperBeam - BetaBeam synergy: CP, T and CPT
No other realistic scenario can offer CP, T and CPT searches at the same time in the same detector!!!!
CP Searches
• SuperBeam running with νµ and ν µ .
• Beta Beam running with 6 He (ν e ) and 18 Ne (νe ).
T searches
• Compare Super Beam p(νµ → νe ) with Beta Beam 18 Ne p(νe → νµ )
• Compare Super Beam p(ν µ → ν e ) with Beta Beam 6 He p(ν e → ν µ ).
CPT searches
• Compare Super Beam p(νµ → νe ) with Beta Beam 6 He p(ν e → ν µ ).
• Compare Super Beam p(ν µ → ν e ) with Beta Beam 18 Ne p(νe → νµ )
In case of small values of θ13 the most powerful combination to discover Leptonic CP would be however a single T search
with neutrinos (SuperBeam νµ with BetaBeam νe ).
54
Beta Beam Super Beam synergy: results
δ
SUPER BEAM ONLY
150
100
50
δm212 = 7 · 10−5 eV 2 , θ13 = 4◦ , δCP = −π/2
0
-50
10 yrs (4400 kton/yr)
SuperBeam
Beta Beam
-100
νµ
-150
0
1
2
3
4
5
6
7
νe
(8 yrs)
(He 6 )
(Ne18 )
36698
23320
40783
55749
Total oscillated
314
67
193
117
CP-Odd oscillated
102
-64
61
-95
Beam background
141
113
/
/
37
50
60
31
CC events (no osc, no cut)
δ
νe
(2 yrs)
8
θ13
SUPER BEAM + BETA BEAM
νµ
150
100
50
Detector bkg.
0
-50
-100
-150
0
1
2
3
4
5
6
7
8
θ13
55
Final CP sensitivity.
∆m122(x10-4) eV2
After Moriond, very preliminary
Nufact
SPL SuperBeam
Beta Beam
SB+BB, 440 kton
1
SB+BB, 1 Mton
Best LMA, hep-ph/0212127
0.5
JHF Phase I
sensitivity on θ13
0
10
-4
10
-3
-2
10 2
sin θ 13
56

tsearch v1 6

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