Potentiality of a non stardard bBeam complex

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Potentiality of a non stardard b-Beam complex

• Pasquale Migliozzi
• INFN Napoli

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!!!WARNING!!!

• The physics potential of the BB of any g has been
  evaluated by several groups
• However, solid feasibility studies from the
  accelerator side are still missing, although some
  interesting ideas are on the market
• The BB are in principle a great idea, but we
  need more studies (regardless of the g option) to
  endorse their practical realization
• Q which flux at different gs?

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Future neutrino oscillation exps
Running, constructing or approved experiments
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Possible scenarios after first results of the
planned experiments and implications

• q13 is so small (lt 3, sin22q13 0.01) that all
  give null result
• We need a cheap experiment to probe sin22q13
  values down to O(0.001 - 0.0001)
• q13 is larger than 3 (sin22q13 0.01)
• We need an experiment (or more than one) to
• Measure q13 more precisely
• Discover d (if not done yet) or precisely measure
  it
• Measure the sign of Dm213
• Measure q23 (is it ?45?)
• NB Independently of the scenario the worsening of
  the experimental sensitivity due to the eightfold
  degeneracy has to be taken into account

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Possible strategy(detector side)

• We think that one should figure out the best
  setup depending on the results of phase I
  experiments
• Null result for q13 are we ready to risk several
  billions ?
• NO, it is better to try a cheap, although not the
  ultimate, approach to two important parameters
  like q13 and d
• Observation of a non vanishing q13 are we ready
  to invest several billions ?
• YES, since there is the possibility to fully
  measure the PMNS mixing matrix

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The b-beam (BB) role

• The BB was born in 2001 when P. Zucchelli put
  forward the idea to produce pure (anti-)ne beam
  from the decay of radioactive ions
• Originally the BB was thought as a low (g100)
  energy neutrino beam and its performance studied
  in combination with a Super-Beam (SB), by
  assuming a 130 km baseline and 1 Mton detector
  located at Frejus (M. Mezzetto et al.)
• However, very recently (december 2003) the
  possibility of medium/(very) high energy BB was
  put forward (see hep-ph/0312068)
• What is the impact of the BB (low, medium,
  (very-)high g) in the future of neutrino
  oscillation experiments?

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Sensitivity to q13
c2 analysis
Feldman Cousins
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Comparison of standard g BB with some of the
future projects
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Parameter extraction in presence of signal
(I)with a standard g BB plus a SB
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Parameter extraction in presence of signal (II)
with a standard g BB plus a SB
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Why high g BB?

• statistics increases linearly with E (cross
  section) ? increase rates (very important for
  anti-neutrinos)
• longer baseline ? enhance matter effects ?
  possibility to measure the sign of Dm213
• increase the energy ? easier to measure the
  spectral information in the oscillation signal ?
  important to reduce the intrinsic degeneracies
• Atmospheric background becomes negligible (this
  is a major background source in the low energy
  option) ? the bunching of the ions is not more a
  crucial issue

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Which gs?

• Use a refurbished SPS with super-conducting
  magnets to accelerate ions
• Maximum g600
• Use the LHC to accelerate ions
• Up to g2488 for 6He and 4158 for 18Ne

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How to exploit high g BB?

• Phase I exps give null result
• See hep-ph/0405081 for a cheap detector and
  extremely sensitive to q13 experiment
• Phase I discover q13
• See Nucl.Phys.B695217-240,2004 for possible
  setups to search for d
• New ideas

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A proposal for a cheap detector
Signal an excess of horizontal muons in
coincidence with the beam spill (possible thanks
to the BB flavour composition)

• Number of unoscillated events increase
  linearly with E
• Range of muons increase linearly with E as
  well. The effective volume of rock contributing
  to the statistics increase linearly with E

We gain a quadratic increase of the sensitivity
if we increase g and we reduce the detector cost
by order of magnitudes!

• The cost of the detector increases with the
  surface and not with the volume

We loose the possibility to fully reconstruct the
events
P.M. F. Terranova, A. Marotta, M. Spinetti
hep-ph/0405081
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Schematic view of the detector
Instrumented surface 15x15 m2 (one LNGS
Hall) Thickness at least 8lI (1.5 m) of iron
for a good p/m separation Iron detector
interleaved with active trackers (about 3kton)
Rock
ne? nm
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A possible scenario BB from CERN to Gran Sasso

• A cavern already exists at GS, but
• Too small to host 40 kton WC or LAr detectors
• On peak exp requires En 1-2 GeV (g 350/580) ?
  too small to efficiently exploit iron detectors
• What happens if for g gt 1000 (i.e. off-peak
  experiment)?
• The oscillation probability decreases as g-2
• The flux increases as g2
• The cross-section and the effective rock volume
  increase both as g
• Matter effects cancel out at leading order even
  if the baseline is large
• We recover the quadratic increase of sensitivity
  but we test now CP-even terms and no matter
  effects

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Event rate
Beam assumptions 1.1x1018 decays per year of 18Ne
2.9x1018 decays per year of 6He Applied cuts 2
GeV energy cut in a 20 cone
NB In case of a smaller of decays one may
instrument more surfaces
100 oscillated events/year 9.3x104 (ne _at_
g2500) 2.0x104 (anti ne _at_ g1500) 7.9x105 (ne _at_
g4158) 2.1x105 (anti ne _at_ g2488)
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Sensitivity of a massless detector located 730
km from a (very)high-g BB
test sin22q13 values down to 10-3-10-4!!!
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Comparison of very-high g BB with some of future
projects
In case of null result very difficult to build
new facilities!
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Two setups studied for the medium/high g options

• Medium (350) and high (1500) g for medium (730
  km) and far (3000 km) baselines
• Water detector (UNO) like 1 Mton mass. Includes
  full simulation of efficiencies and backgrounds
  (only statistical study for high gamma option)
• Running time 10 years
• Full analysis (including the eightfold
  degeneracy, all systematics on cross-sections,
  detector, beam, performance at small q13, etc.)
  still to be done

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Results
99 CL
J.Burguet-Castell et al., Nucl.Phys.B695217-240,2
004
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Comments

• The idea of medium/(very) high-g BB is very
  appealing
• The medium scenario has been put forward in
  Nucl.Phys.B695217-240,2004 to measure q13, d
  and the sign of Dm213, but more studies are
  needed to fully exploit its potential (i.e. the
  q23 ambiguity)
• However, we think this is not the optimal
  solution
• It foresees the construction of a 1 Mton
  detector!
• There are no place in the world able to host it
• It is very expensive, so to risky to build if
  phase I exps give null results
• The optimal solution is the (very-)high g
  scenario
• In case of null result of phase I exps it allows
  a cheap investigation of very small values of
  sin22q13 (see hep-ph/0405081)
• In case of positive result of phase I exps it
  allows a complete study of the PMNS matrix
  through different channels, see next slides for
  details
• On top of that it makes possible the usage of
  magnetized calorimeters which are smaller (40
  kton -gt about 104 m3) than WC detectors (1 Mton
  -gt about 106 m3) ? cheaper (easier) civil
  engineer costs

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Preliminary studies/ideas on how to use the
(very-)high g BB

• A. Donini, PM, S. Rigolin,

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BB vs NuFact spectra
NuFact
Ne
He
Ne
He
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Expected rates (1ktonx1year)
NB There is less than a factor 10 difference in
the evts BB allows simultaneous run with n and
anti-n, while NuFact does not
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Potentiality of a (very-)high g BB

• Simultaneous search for ne?nm (golden) and ne?nt
  (silver) channels
• This combination is highly efficient in removing
  the intrinsic and the sign degeneracy (see
  A.Donini, D.Meloni, P.Migliozzi
  Nucl.Phys.B646321-349,2002)
• Simultaneous search for n and anti-n channels
  (i.e. 1 year BB ? 2 years NuFact)
• Detectors 40kton magnetized iron detector (MID)
  at 3000km 5kton ECC detector at 730km
• The physics potential of this setup is currently
  under study as well as its comparison with a
  NuFact

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Very preliminary results at a high-g BBwith
golden plus silver channels
68, 90, 99 CL
MIDECC
MID
Octan clone
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High-g 1/10 statistics
High-g full statistics
Standard-g full statistics
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Conclusion

• The BB is a very nice n-producer
• The potentialities of BB with a large variety of
  g have been studied and (as expected) the higher
  the g (large neutrino energies) the better the
  physics potential is
• However
• MORE STUDIES FROM THE ACCELERATOR SIDE ARE NEEDED
  INDEPENDENTLY OF THE g OPTION
• IN PARTICULAR A SOLID ESTIMATE OF THE EXPECTED
  FLUXES FOR THE DIFFERENT OPTIONS IS NEEDED

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Machine issues decay ring
Main cost is civil engineering Low gamma 6.8km,
5T, useful decay fraction 37 Higher gammas Use
the acceleration ring also for storage and build
a small straight section pointing toward the
detector and a curved section to reconnect (very
high gamma 3km straight section, 9T, 8km curved)
Cons full occupancy of the machine (interference
with the LHC) useful decay fraction 10 can be
easily recovered instrumenting more than one LNGS
hall
Pros cost of civil engineering comparable (35)
with lower gamma
Intermediate gammas Both possibilities can be
considered for a dedicated decay ring g350,
11km, 9T, useful decay fraction is 22
The actual cost mainly depends on the outcome of
the RD for the energy upgrade of the LHC or the
VLHC (maximum field available)
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Machine issues occupancy

• Not a problem for an intermediate gamma with
  dedicated decay ring
• (LHC/S-SPS used only in the accelerating phase)
• Not a problem for a very high gamma BB (VHG) if
  postponed to the energy upgrade of the LHC (two
  rings coexisting in the same tunnel and sharing
  the same cryogenics)
• Very unlikely for a VHG unless we can store gtgt
  5 1014 ions

Machine issues intensity

• Intermediate gamma reduction of a factor of 5
  of the decays per second
• can be recovered by a faster PS and ion
  collection time
• VHG reduction of a factor of 20-40 but no need
  of asymmetric merging
• (no background from atm) multibunch stacking in
  the LHC before acceleration or re-optimise the
  choice of the isotope (fast PS!)