physics with a very long neutrino factory baseline ids meeting cern march 30, 2007 walter winter...

Physics with a very long neutrino Physics with a very long neutrino factory baselinefactory baseline

IDS MeetingIDS MeetingCERNCERN

March 30, 2007March 30, 2007

Walter WinterWalter WinterUniversität WürzburgUniversität Würzburg

March 30, 2007 IDS CERN - Walter Winter 2

ContentsContents Introduction: Magic baselineIntroduction: Magic baseline Open questionsOpen questions A more realistic density modelA more realistic density model Answers: e.g.: which detector locations?Answers: e.g.: which detector locations? More physics applications:More physics applications:

– Matter density measurement Matter density measurement – 1313 precision measurement precision measurement– Octant degeneracyOctant degeneracy– MSW effect sensitivityMSW effect sensitivity

Physics case for a very long baselinePhysics case for a very long baseline

(mainly based on:Gandhi, Winter: “Physics with a very long neutrino factory baseline”, Phys. Rev. D75 (2007) 053002, hep-ph/0612158)


Appearance channels: Appearance channels: ee

Information: Information: 1313, , CPCP, mass hierarchy (via A), mass hierarchy (via A)(Cervera et al. 2000; Freund, Huber, Lindner, 2000; Akhmedov et al, 2004)

Expansion in small sin 2Expansion in small sin 21313 and and ::


Idea of the “Magic baseline”Idea of the “Magic baseline” Idea:Idea:

Yellow term = 0Yellow term = 0 independent independent of E, oscillation parametersof E, oscillation parameters

Purpose: Purpose: “Clean” measurement of “Clean” measurement of 1313 and mass hierarchy and mass hierarchy

No dependence on E, osc. parametersNo dependence on E, osc. parameters Drawback: No Drawback: No CPCP measurement at magic baseline measurement at magic baseline

combine with shorter baseline, such as L=3 000 kmcombine with shorter baseline, such as L=3 000 km


Magic baseline: QuantifiedMagic baseline: QuantifiedUse two-baseline space (LUse two-baseline space (L11,L,L22) with (25kt, 25kt) and compute ) with (25kt, 25kt) and compute 1313

reach including correlations and degeneracies:reach including correlations and degeneracies:

Animation in Animation in

1313--CPCP-space:-space:

(Huber, Winter, 2003)sin2213

CP

(3; red: measure for risk – in this case m21

2)


Open questionsOpen questions Which density forWhich density for

conditioncondition ? ?

Not exactly known Not exactly known from geophysics!from geophysics!

Is the constant density approximation sufficient?Is the constant density approximation sufficient? Is the expansion in Is the expansion in and and 1313 accurate enough? accurate enough?

What happens if my preferred detector location is not What happens if my preferred detector location is not exactly on the “magic baseline”?exactly on the “magic baseline”?

Is there a preferred detector site from geophysics?Is there a preferred detector site from geophysics?

Matter density uncertainties in 3D models ~ 5%

(http://cfauvcs5.harvard.edu/lana/rem/mapview.htm)


A more realistic density profile modelA more realistic density profile model

PREM profile PREM profile approximated by 7 profile approximated by 7 profile steps between L~6000 km steps between L~6000 km and 9000 km „Profileand 9000 km „Profile77““ Efficient for computationEfficient for computation More realistic for modelMore realistic for model

Dashed: Often used Dashed: Often used baseline-averaged densitybaseline-averaged density

(Gandhi, Winter, 2006)


Constant reference density Constant reference density RefRef

Idea: Find constant dens. which best matches ProfileIdea: Find constant dens. which best matches Profile77: : RefRef

Method: Minimize total Method: Minimize total 22 from all channels between from all channels between ProfileProfile77 and and Ref Ref (simulate Profile(simulate Profile77 and fit and fit RefRef for same osc. Params) for same osc. Params)

Least contribution of profile effect to statistical analysisLeast contribution of profile effect to statistical analysis



Constant reference densityConstant reference density RefRef = Mean density? = Mean density?

Answer: ~ 5% offAnswer: ~ 5% offReason: long constant Reason: long constant density layer dominatesdensity layer dominates

Parameter dependence Parameter dependence ((1313, , ) ) strongest for small strongest for small 1313, , but there but there 22 function function shallowshallow(last slide) (last slide)


(see e.g. Akhmedov, 2000)


How we address the main questionsHow we address the main questions

What if the detector location is off the MB?What if the detector location is off the MB?Show sensitivity as a function of baselineShow sensitivity as a function of baseline

Unknown matter density (geophysics):Unknown matter density (geophysics):What if What if RefRef wrong by ~5%? wrong by ~5%?Show results for 0.95 Show results for 0.95 RefRef and 1.05 and 1.05 RefRef

Profile effects: How well does a constant Profile effects: How well does a constant density simulate the matter density profile?density simulate the matter density profile?Is the actual sensitivity better or worse?Is the actual sensitivity better or worse?Show results for ProfileShow results for Profile77 and and RefRef


1313 sensitivity sensitivity

Strong impact for one baseline onlyStrong impact for one baseline only Exact detector location not so important for combination Exact detector location not so important for combination

with shorter baseline (L ~ 7000 – 9000 km)with shorter baseline (L ~ 7000 – 9000 km)



CP violation measurementCP violation measurement

Very long Very long baseline clearly baseline clearly helpshelps

Optimal Optimal L ~ 7700 km L ~ 7700 km +- 500 km+- 500 km


Very long baseline Very long baseline helps for helps for L ~ 7000 km to L ~ 7000 km to 9000 km, but small 9000 km, but small absolute impactabsolute impact

Profile effect Profile effect enhances perform.enhances perform.

No clear No clear preference of a preference of a very long very long baseline baseline (poor statistics (poor statistics dominated)dominated)


Consequences for detector locationsConsequences for detector locations Mass hier.: L ~ 6000 - 9000 km good for sinMass hier.: L ~ 6000 - 9000 km good for sin22221313 > 10 > 10-4-4

Choose, e.g., L ~ 7000 – 9000 km:Choose, e.g., L ~ 7000 – 9000 km:


Some answersSome answers Magic baseline is a very accurate description for one Magic baseline is a very accurate description for one

baseline onlybaseline only Very long baselines between ~ 7000 km and 9000 km Very long baselines between ~ 7000 km and 9000 km

OK if second detector at shorter LOK if second detector at shorter L In this case, little impact from profile effects and poor In this case, little impact from profile effects and poor

geophysics information geophysics information Mean density is not a good choice for a constant Mean density is not a good choice for a constant

reference densityreference density Use Use RefRef further on, which reproduces profile very well further on, which reproduces profile very well

Profile effects improve absolute sensitivity somewhat Profile effects improve absolute sensitivity somewhat compared to constant densitycompared to constant density

Further applications of aFurther applications of avery long neutrino factory baselinevery long neutrino factory baseline


Matter density measurementMatter density measurement IdeaIdea: Treat : Treat as yet another as yet another

oscillation parameter to be oscillation parameter to be measured; marginalize measured; marginalize oscillation parameters!oscillation parameters!

Comes „for free“ from very Comes „for free“ from very long baseline!?long baseline!?

Two different models:Two different models:1.1. Measure Measure RefRef

2.2. Measure Measure LMLM

(lower mantle density)(lower mantle density)(Winter, 2005;

Minakata, Uchinami, 2006; Gandhi, Winter, 2006)

Lower mantle density


Matter density: Geophysical use?Matter density: Geophysical use? Example:Example:

Plume hypothesisPlume hypothesis A precisionA precision

measurement << 1%measurement << 1%could discriminatecould discriminatedifferent geophysicaldifferent geophysicalmodelsmodels

Possible selectorPossible selectorof detectorof detectorlocations?locations?

(Courtillot et al., 2003; see talk from B. Romanowicz, Neutrino geophysics 2005)


Results for one-parameter measurementResults for one-parameter measurement Assume that only one Assume that only one

parameter measuredparameter measured For large For large 1313, < 1% , < 1%

precision at 3precision at 3 Indep. confirmed byIndep. confirmed by

Minakata, UchinamiMinakata, Uchinami(for one baseline)(for one baseline)

(Gan

dhi,

Win

ter,

200

6)


A more sophisticated modelA more sophisticated model Assume that upper mantle density (Assume that upper mantle density (UMUM))

only known with certain precision:only known with certain precision: (Gandhi, Winter, 2006)


Reduction of matter density uncertaintyReduction of matter density uncertainty

Use of very long Use of very long baseline reduces the baseline reduces the impact of matter impact of matter density uncertainties density uncertainties as wellas well

No need for extra No need for extra geophysics effort if geophysics effort if two baselines usedtwo baselines used

(Huber, Lindner, Rolinec, Winter, 2006)

(dashed: 2%, solid: 5% matter density uncertainty)


1313 precision measurement precision measurement

Bands: dependence on Bands: dependence on (worst case, median, best case) (worst case, median, best case)

(Gandhi, Winter, 2006) Example: sinExample: sin22221313 = 0.001: = 0.001:


Resolving the Resolving the 2323 degeneracy degeneracy

4000 km alone: Problems with 4000 km alone: Problems with degs for intermediate degs for intermediate 1313

7200 km alone: 7200 km alone: No sensitivity for small No sensitivity for small 1313

4000 km + 7200 km: 4000 km + 7200 km: Good for all Good for all 1313



Null result if solar effectsNull result if solar effectsneglected:neglected:

But solar term:But solar term:

Note thatNote that

i.e., effect increases with baseline!i.e., effect increases with baseline!

MSW effect sensitivity for MSW effect sensitivity for 1313=0=0

(Winter, 2004)

(Freund et al, 1999)

5


Physics case for a very long NF baselinePhysics case for a very long NF baseline

sin221310-1

10-3

„Large“

• Reduced impact of matter density uncertainty

• Better CP violation performance

• Precise matter density measurement

• Guaranteed mass hierarchy sensitivity

• Correlation and degeneracy resolution

• Improved precision measurement of CP

• Information on the matter density

• Maximized 13 and mass hier. sens. reach

• Correlation and degeneracy resolution

• Improved precision measurement of CP

• MSW effect sensitivity

• Potentially future mass hier. sensitivity

10-2

10-4

„Medium“

„Small“

„Zero“

• Helps for the 23 measurement

• Helps for octant degeneracy resolution

• Improves 13

precision measurement

(see: Gandhi, W

inter, 2006)


SummarySummary Magic baseline description holds for all practical Magic baseline description holds for all practical

applications, but use applications, but use RefRef instead of mean density instead of mean density

Two baseline setup rather insensitive to very Two baseline setup rather insensitive to very long baseline length (but: VL baseline clearly long baseline length (but: VL baseline clearly helps)helps)

Geophysics spin-off may prefer specific detector Geophysics spin-off may prefer specific detector locations; needs more investigationlocations; needs more investigation

Physics case for very long baseline no matter Physics case for very long baseline no matter how big how big 1313 is (if neutrino factory is built) is (if neutrino factory is built)

physics with a very long neutrino factory baseline ids meeting cern march 30, 2007 walter winter...

Documents

ids cern walter winteridea

ids cern walter winterhow

matter density profile

mean density

matter density uncertainties

constant density layer

shorter baseline

realistic density modelanswers