Transcript A neutrino beam to IceCube/PINGU? (PINGU = “Precision IceCube Next-Generation Upgrade“) NPAC (Nuclear/Particle/Astro/Cosmo) Forum UW-Madison, USA May 15, 2012 Walter Winter Universität Würzburg.

A neutrino beam to
IceCube/PINGU?
(PINGU = “Precision IceCube Next-Generation Upgrade“)
NPAC (Nuclear/Particle/Astro/Cosmo) Forum
UW-Madison, USA
May 15, 2012
Walter Winter
Universität Würzburg
Contents
 Introduction
 Oscillation physics using a core-crossing
baseline
 Neutrino beam to PINGU:
Beams and detector parameterization
 Detector requirements for large q13
 Comments on LBNE reconfiguration
 Summary
2
Three flavor mixing
 Use same parameterization as for CKM matrix
Potential CP violation ~ q13
(sij = sin qij cij = cos qij)
=
(
)(
x
)(
x
)
Pontecorvo-Maki-Nakagawa-Sakata matrix
3
q13 discovery 2012
 First evidence from T2K, Double Chooz
 Discovery (~ 5s) independently (?)
by Daya Bay, RENO
Daya Bay 3s
1s error bars
(from arXiv:1204.1249)
4
Mass spectrum/hierarchy
8
8
Normal
Inverted
 Specific models typically
come together with specific
MH prediction (e.g.
textures are very different)
 Good model discriminator
(Albright, Chen, hep-ph/0608137)
5
Three flavors: Summary
 Three flavors: 6 params
(3 angles, one phase; 2 x Dm2)
Atmospheric
oscillations:
Amplitude: q23
Frequency: Dm312
Coupling: q13
Suppressed
effect: dCP
Solar
oscillations:
Amplitude: q12
Frequency: Dm212
(Super-K, 1998;
Chooz, 1999;
SNO 2001+2002;
KamLAND 2002;
Daya Bay, RENO
2012)
 Describes solar and atmospheric neutrino
anomalies, as well as reactor antineutrino disapp.!
6
Consequences
Huber, Lindner, Schwetz, Winter, 2009
 Parameter space
for dCP starts to
become
constrained;
MH/CPV difficult
(need to exclude
dCP=0 and p)
 Need new facility!
7
Mass hierarchy discovery?
 90% CL, existing equipment
 3s, Project X and T2K with
proton driver, optimized
neutrino-antineutrino run plan
Huber, Lindner, Schwetz, Winter, JHEP 11 (2009) 44
8
Mass hierarchy measurement?
 Mass hierarchy [sgn(Dm2)] discovery possible
with atmospheric neutrinos?
(liquid argon, HyperK, MEMPHYS, INO, PINGU?, LENA?, …)
Barger et al, arXiv:1203.6012;
IH more challenging
Perhaps different
facilities for MH and CPV
proposed/discussed?
 However: also long-baseline proposals!
(LBNO: superbeam ~ 2200 km – LAGUNA design study;
CERN-SuperK ~ 8870 km – Agarwalla, Hernandez, arXiv:1204.4217; South Pole: Dick et al, 2000)9
Oscillation physics using a
core-crossing baseline
What is PINGU?
What is PINGU?
2012
11
PINGU fiducial volume?
 A few Mt fiducial
mass for
superbeam
produced with
FNAL main injector
protons (120 GeV)
LBNEbeam
(Jason Koskinen)
12
Beams to PINGU?
 Labs and potential detector locations (stars) in
“deep underground“ laboratories:
All these baselines cross the Earth‘s outer core!
(Agarwalla, Huber, Tang, Winter, 2010)
FNAL-PINGU: 11620 km
CERN-PINGU: 11810 km
RAL-PINGU: 12020 km
JHF-PINGU: 11370 km
13
Matter profile of the Earth
… as seen by a neutrino
Inner
core
(PREM: Preliminary Reference Earth Model)
Core
14
Matter effect (MSW)
(Wolfenstein, 1978;
 Ordinary matter:
Mikheyev, Smirnov,
electrons, but no m, t
1985)
 Coherent forward
scattering in matter:
Net effect on electron flavor
 Hamiltonian in matter
(matrix form, flavor space):
Y: electron
fraction ~
0.5
(electrons
per
nucleon)
15
Parameter mapping
 Oscillation probabilities in
vacuum:
matter:
Matter resonance:
In this case:
- Effective mixing maximal
- Effective osc. frequency
minimal
 MH
Resonance energy:
For nm appearance, Dm312:
- r ~ 4.7 g/cm3 (Earth’s
mantle): Eres ~ 6.4 GeV
- r ~ 10.8 g/cm3 (Earth’s outer
core): Eres ~ 2.8 GeV
16
Mantle-core-mantle profile
(Parametric enhancement: Akhmedov, 1998; Akhmedov, Lipari, Smirnov, 1998; Petcov, 1998)
 Probability for FNAL-PINGU (numerical)
!
Interference
Parametric enhancement
through mantle-core-mantle
profile of the Earth.
Unique physics potential!
Core
resonance
energy
Mantle
resonance
energy
Threshold
effects
expected at:
2 GeV
4-5 GeV
Beam energy
and detector threshold
have to pass ~ 2 GeV!
Naive L/E scaling
does not apply!
17
Neutrino beam to PINGU?
Beams and detector
parameterization
Possible neutrino sources
There are three possibilities to artificially produce
neutrinos
 Beta decay:
 Example: Nuclear reactors, Beta beams
 Pion decay:
Superbeam
 From accelerators:
Pions
Protons
Target
Selection,
focusing
Muons,
neutrinos
Decay
tunnel
Neutrinos
Absorber
 Muon decay:
 Muons produced by pion decays! Neutrino Factory
19
Considered setups
 Single baseline reference setups:
L [km]
 Idea: similar beam, but detector replaced by
PINGU/MICA [need to cover ~ 2 – 5 GeV]:
(for details: Tang, Winter, JHEP 1202 (2012) 028, arXiv:1110.5908; Sec. 3)
20
Oscillation channels
Want to study ne-nm oscillations
 Beta beams:
 In principle best choice for PINGU (need muon flavor ID only)
 Superbeams:
 Need (clean) electron flavor sample. Difficult?
 Neutrino factory:
 Need charge identification of m+ and m- (normally)
21
PINGU fiducial volume?
In principle: Mton-size detector in relevant ranges:
Eres (DE) = x E
Veff
Eth
Unclear how that evolves with cuts for flavor-ID etc. (background
reduction); MICA even larger?
 Use effective detector parameterization to study requirements: Eth, Veff, Eres
(Tang, Winter, JHEP 1202 (2012) 028; Veff somewhat smaller than J. Koskinen ‘s current results)
22
Detector paramet.: mis-ID
misID:
fraction of events of a
specific channel
mis-identified as signal
misIDtracks
<< misID <~ 1 ?
(Tang, Winter, JHEP 1202 (2012) 028)
23
Detector requirements
for large q13
Superbeam (LBNE-like)
Fraction of dCP
 Mass hierarchy
measurement
very robust
(even with large
misID and total
rates only
possible)
(misIDtracks = 0.01)
(Tang, Winter, JHEP 1202 (2012) 028)
25
Low-intensity alternative?
 Use existing equipment, new beam line
 Here: use most conservative assumption
NuMI beam, 1021 pot (total), neutrinos only
[compare to LBNE: 22+22 1020 pot without Project X ~ factor
four higher exposure than the one considered here]
(FERMILAB-PROPOSAL-0875, NUMI-L-714)
 Low intensity allows for shorter decay pipe
(rough estimate: ~ 100 m for 700kW beam)
 Advantage: Peaks in exactly the right energy
range for the parametric enhancement due to
the Earth‘s core
(Tang, Winter, JHEP 1202 (2012) 028)
26
Detector parameterization
 Challenges:
 Electron flavor ID
 Systematics (efficiency, flux normalization  near
detector?)
 Energy resolution
 Make very (?) conservative assumptions here:
 Fraction of mis-identified muon tracks (muon tracks may
be too short to be distinguished from signal) ~ 20%
 Irreducible backgrounds (zeroth order assumption!):
 Intrinsic beam background
 Neutral current cascades
 nm  nt cascades (hadronic and electromagnetic cascades
indistinguishable)
 Systematics uncorrelated between signal and
background
 No energy resolution (total rates only)
(for details on parameterization: Tang, Winter, JHEP 1202 (2012) 028)
27
Event rates
(Daya Bay best-fit)
Normal hier. Inv. hierarchy
Signal
1560
54
39
511
59
750
3
4
Neutral currents
2479
2479
Total backgrounds
3032
3292
Total signal+backg.
4592
Backgrounds:
ne beam
Disapp./track mis-ID
nt appearance
>18s
(stat. only)
3346
28
NuMI-like beam to PINGU?
All irreducible backgrounds included
(Daya Bay best-fit; current parameter
uncertainties, marginalized over)
GLoBES 2012
 Very robust mass hierarchy measurement (as long as
either some energy resolution or control of systematics);
track mis-identification maybe too conservative
29
Probabilities: dCP-dependence
 There is a rich dCP-phenomenology:
NH
(probably works for NH only!?) 30
Upgrade path towards dCP?
 Measurement of dCP
in principle possible,
but challenging
 Requires:
 Electromagnetic
shower ID
(here: 1% mis-ID)
 Energy resolution
(here: 20% x E)
 Maybe: volume
upgrade
(here: ~ factor two)
 Project X
= LBNE +
Project X!
same beam
to PINGU
 Performance and
optimization of
PINGU, and
possible upgrades
(MICA, …) require
further study
(Tang, Winter, JHEP 1202 (2012) 028)
31
Beta beam
 Similar results
for mass hierarchy
measurement (easy)
 CPV less promising:
long L, asymmetric
beam energies
(at least in CERN-SPS limited case
g~656 for 8B and g=390 for 8Li)
although moderate
detector requirements
(misID ~ 0.001, Eth=2 GeV, Eres=50% E, Veff=5 Mt)
(Tang, Winter, JHEP 1202 (2012) 028)
32
Neutrino factory
 No magnetic field, no charge identification
 Need to disentangle Pem and Pmm by energy
resolution:
(from: Tang, Winter, JHEP 1202 (2012) 028;
for non-magnetized detectors, see Huber, Schwetz, Phys. Lett. B669 (2008) 294)
33
nt contamination
 Challenge:
(sin22q13=0.1)
Reconstructed at
lower energies!
(Indumathi, Sinha, PRD 80 (2009) 113012;
Donini, Gomez Cadenas, Meloni,
JHEP 1102 (2011) 095)
 Choose low
enough Em to avoid nt
(Tang, Winter, JHEP 1202 (2012) 028)
 Need event migration matrices (from detector simulation)
for reliable predictions! (neutral currents etc)
34
Matter density measurement
Example: LBNE-like Superbeam
 Precision ~
0.5% (1s)
 Highly
competitive to
seismic waves
(seismic shear
waves cannot
propagate in
the liquid core!)
(Tang, Winter, JHEP 1202 (2012) 028)
35
LBNE reconfiguration
(some personal comments)
Thanks discussions with:
A. de Gouvea, F. Halzen, J. Hylen, B. Kayser, J. Kopp, S. Parke,
PINGU collaboration, …
D ~ 600M$
37
Landscape (before reconfiguration)
 LBNE one out of
many options to
measure CPV
 Can this reach
be matched in a
phased
approach?
 How can one
define a truly
unique
experiment for
<= 600M US$?
 How would one
react if T2HK
happens?
(P. Huber)
38
Reconfiguration options?
… or how to spend 600 M$
 New detector, existing beam line
 MINOS site (L=735 km)
 NOvA site (L=810 km)
 New site?
 New (smaller) detector, new beam line (~300 M$)
 Smaller detector in Homestake (L=1300 km)
 Surface detector at Homestake (L=1300 km)
 New beam line (<= 550 M$?), (then) existing detector
 PINGU (L=11620 km)
…
Idea ~ 2 weeks old
39
Best physics concept?
Homestake, on-axis
NuMI
beam
line
New
beam
line
(Barger, Huber, Marfatia, Winter, PRD 76 (2007) 053005)
40
Conclusion:
LBNE – smaller version?
This is what
T2HK
cannot do
MH, 5s
This is what
T2HK
can also do
 How many s
does one
need?
 Combination
of experiments
tolerable as
physics
result?
41
Conclusions: FNAL-PINGU?
 FNAL-PINGU
 Megaton-size ice detector as upgrade of DeepCore with lower threshold; very
cost-efficient compared to liquid argon, water
 Unique mass hierarchy measurement through parameteric enhancement;
proton beams from main injector may just have right energy
 In principle, MH even with counting experiment measurable (compared to MH
determination using atmospheric neutrinos)
 Challenges on beam side (questions from PINGU meeting):
 Tilt of beam line – feasibility, cost?
 Near detector necessary? Maybe not, if 10% systematics achievable …
 Beam bunching (to reduce atmospheric backgrounds)?
NB: very low exposure required for MH; shorter decay pipe, one horn only, …?
 Perspectives
 CP violation challenging (requires energy resolution, flavor identification), but
not in principle excluded; needs further study on detector side
 Measurement of Earth‘s core density, in principle, possible
(Tang, Winter, JHEP 1202 (2012) 028)
 Upgrades of PINGU discussed (MICA)
 Truly unique and spectacular long-baseline experiment with no other
alternative proposed doing similar physics!?
 The LBNE alternative if T2HK is going to be funded?
42
BACKUP
NOvA+INO (atm.)?
MH, 3s
(Blennow, Schwetz,
arXiv:1203.3388)
44
NF: Precision measurements?
… only if good enough
energy resolution
~ 10% E and
misID (cascades
versus tracks)
<~ 1% can be
achieved!
Requires further
study …
(Tang, Winter, JHEP 1202 (2012) 028)
45
Beams: Appearance channels
(Cervera et al. 2000; Freund, Huber, Lindner, 2000; Akhmedov et al, 2004)
 Antineutrinos:
 Magic baseline:
L~ 7500 km: Clean measurement of q13 (and mass
hierarchy) for any energy, value of oscillation parameters!
(Huber, Winter, 2003; Smirnov 2006)
In combination with shorter baseline, a wide range of very
long baseline will do! (Gandhi, Winter, 2006; Kopp, Ota, Winter, 2008)
46
Quantification of performance
Example: CP violation discovery
Best performance
close to max.
CPV (dCP = p/2 or
Sensitive
region as a
function of true
q13 and dCP
3p/2)
dCP values
now stacked
for each q13
No CPV discovery if
dCP too close to 0 or p
3s
~ Precision in
quark sector!
Read: If
sin22q13=10-3,
No CPV discovery for
all values of dCP
we
expect a
discovery for 80%
of all values of dCP
47
Effective volume
 Difference Eth = 2 GeV, Veff=5 Mt to actual
(energy-dependent) fiducial volume:
(Tang, Winter, JHEP 1202 (2012) 028)
48
VL baselines (1)
Note:
Pure baseline effect!
A 1: Matter
resonance
Prop. To L2;
compensated by
flux prop. to
1/L2
(Factor 1)(Factor 2)
(Factor
1)2
(Factor
2)2
49
VL baselines (2)
 Factor 1:
Depends on energy;
can be matter
enhanced for long L;
however: the longer
L, the stronger
change off the
resonance
 Factor 2:
Always suppressed
for longer L;
zero at “magic
baseline” (indep. of
E, osc. Params)
(Dm312 = 0.0025, r=4.3 g/cm3, normal hierarchy)
 Factor 2 always suppresses CP and solar terms
for very long baselines; note that these terms
include 1/L2-dep.!
50