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Physics with a very long neutrino factory baseline

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Is there a preferred detector site from geophysics? ... In this case, little impact from profile effects and poor geophysics information ... – PowerPoint PPT presentation

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Title: Physics with a very long neutrino factory baseline


1
Physics with a very long neutrino factory baseline
  • IDS Meeting
  • CERN
  • March 30, 2007Walter Winter
  • Universität Würzburg

2
Contents
(mainly based onGandhi, Winter Physics with
a very long neutrino factory baseline, Phys.
Rev. D75 (2007) 053002, hep-ph/0612158)
  • Introduction Magic baseline
  • Open questions
  • A more realistic density model
  • Answers e.g. which detector locations?
  • More physics applications
  • Matter density measurement
  • q13 precision measurement
  • Octant degeneracy
  • MSW effect sensitivity
  • Physics case for a very long baseline

3
Appearance channels nm ne
Expansion in small sin 2q13 and a
(Cervera et al. 2000 Freund, Huber, Lindner,
2000 Akhmedov et al, 2004)
  • Information q13, dCP, mass hierarchy (via A)

4
Idea of the Magic baseline
  • IdeaYellow term 0 independent of E,
    oscillation parameters
  • Purpose Clean measurement of q13 and mass
    hierarchy
  • No dependence on E, osc. parameters
  • Drawback No dCP measurement at magic baseline
  • combine with shorter baseline, such as L3 000 km

5
Magic baseline Quantified
  • Use two-baseline space (L1,L2) with (25kt, 25kt)
    and compute q13 reach including correlations and
    degeneracies

Animation in q13-dCP-space
(3s red measure for risk in this case Dm212)
dCP
sin22q13
(Huber, Winter, 2003)
6
Open questions
  • Which density forcondition ?Not
    exactly known from geophysics!
  • Is the constant density approximation sufficient?
  • Is the expansion in a and q13 accurate enough?
  • What happens if my preferred detector location is
    not exactly on the magic baseline?
  • Is there a preferred detector site from
    geophysics?

Matter density uncertainties in 3D models
5 (http//cfauvcs5.harvard.edu/lana/rem/mapvi
ew.htm)
7
A more realistic density profile model
  • PREM profile approximated by 7 profile steps
    between L6000 km and 9000 km Profile7
  • Efficient for computation
  • More realistic for model
  • Dashed Often used baseline-averaged density

(Gandhi, Winter, 2006)
8
Constant reference density rRef
  • Idea Find constant dens. which best matches
    Profile7 rRef
  • Method Minimize total Dc2 from all channels
    between Profile7 and rRef (simulate Profile7
    and fit rRef for same osc. Params)
  • Least contribution of profile effect to
    statistical analysis

(Gandhi, Winter, 2006)
9
Constant reference density
  • rRef Mean density?Answer 5 offReason
    long constant density layer dominates
  • Parameter dependence (q13, d) strongest for
    small q13, but there c2 function shallow(last
    slide)

(see e.g. Akhmedov, 2000)
(Gandhi, Winter, 2006)
10
How we address the main questions
  • What if the detector location is off the MB?
  • Show sensitivity as a function of baseline
  • Unknown matter density (geophysics)What if rRef
    wrong by 5?
  • Show results for 0.95 rRef and 1.05 rRef
  • Profile effects How well does a constant density
    simulate the matter density profile?Is the
    actual sensitivity better or worse?
  • Show results for Profile7 and rRef

11
q13 sensitivity
(Gandhi, Winter, 2006)
  • Strong impact for one baseline only
  • Exact detector location not so important for
    combination with shorter baseline (L 7000
    9000 km)

12
CP violation measurement
(Gandhi, Winter, 2006)
  • Very long baseline clearly helps
  • Optimal L 7700 km - 500 km
  • Very long baseline helps for L 7000 km to 9000
    km, but small absolute impact
  • Profile effect enhances perform.
  • No clear preference of a very long baseline
    (poor statistics dominated)

13
Consequences for detector locations
  • Mass hier. L 6000 - 9000 km good for sin22q13
    gt 10-4
  • Choose, e.g., L 7000 9000 km

14
Some answers
  • Magic baseline is a very accurate description for
    one baseline only
  • Very long baselines between 7000 km and 9000 km
    OK if second detector at shorter L
  • In this case, little impact from profile effects
    and poor geophysics information
  • Mean density is not a good choice for a constant
    reference density
  • Use rRef further on, which reproduces profile
    very well
  • Profile effects improve absolute sensitivity
    somewhat compared to constant density

15
Further applications of avery long neutrino
factory baseline
16
Matter density measurement
  • Idea Treat r as yet another oscillation
    parameter to be measured marginalize oscillation
    parameters!
  • Comes for free from very long baseline!?
  • Two different models
  • Measure rRef
  • Measure rLM (lower mantle density)

Lower mantle density
(Winter, 2005 Minakata, Uchinami, 2006
Gandhi, Winter, 2006)
17
Matter density Geophysical use?
  • ExamplePlume hypothesis
  • A precisionmeasurement ltlt 1could
    discriminatedifferent geophysicalmodels
  • Possible selectorof detectorlocations?

(Courtillot et al., 2003 see talk from B.
Romanowicz, Neutrino geophysics 2005)
18
Results for one-parameter measurement
  • Assume that only one parameter measured
  • For large q13, lt 1 precision at 3s
  • Indep. confirmed byMinakata, Uchinami(for one
    baseline)

(Gandhi, Winter, 2006)
19
A more sophisticated model
  • Assume that upper mantle density (rUM)only known
    with certain precision

(Gandhi, Winter, 2006)
20
Reduction of matter density uncertainty
(dashed 2, solid 5 matter density uncertainty)
  • Use of very long baseline reduces the impact of
    matter density uncertainties as well
  • No need for extra geophysics effort if two
    baselines used

(Huber, Lindner, Rolinec, Winter, 2006)
21
q13 precision measurement
  • Example sin22q13 0.001

(Gandhi, Winter, 2006)
  • Bands dependence on d (worst case, median, best
    case)

22
Resolving the q23 degeneracy
(Gandhi, Winter, 2006)
  • 4000 km alone Problems with degs for
    intermediate q13
  • 7200 km alone No sensitivity for small q13
  • 4000 km 7200 km Good for all q13

23
MSW effect sensitivity for q130
  • Null result if solar effectsneglected
  • But solar termNote thati.e., effect
    increases with baseline!

5s
(Freund et al, 1999)
(Winter, 2004)
24
Physics case for a very long NF baseline
10-1
sin22q13
  • Reduced impact of matter density uncertainty
  • Better CP violation performance
  • Precise matter density measurement
  • Helps for the q23 measurement
  • Helps for octant degeneracy resolution
  • Improves q13 precision measurement

Large
10-2
  • Guaranteed mass hierarchy sensitivity
  • Correlation and degeneracy resolution
  • Improved precision measurement of dCP
  • Information on the matter density

Medium
(see Gandhi, Winter, 2006)
10-3
  • Maximized q13 and mass hier. sens. reach
  • Correlation and degeneracy resolution
  • Improved precision measurement of dCP

Small
10-4
  • MSW effect sensitivity
  • Potentially future mass hier. sensitivity

Zero
25
Summary
  • Magic baseline description holds for all
    practical applications, but use rRef instead of
    mean density
  • Two baseline setup rather insensitive to very
    long baseline length (but VL baseline clearly
    helps)
  • Geophysics spin-off may prefer specific detector
    locations needs more investigation
  • Physics case for very long baseline no matter how
    big q13 is (if neutrino factory is built)
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