Unofficial* summary of the Long Baseline Neutrino Experiment (LBNE) physics workshop Seattle, Aug 9 to Aug 11 David Webber August 24, 2010 *Many studies/plots are preliminary. These slides are a representation of the workshop’s discussion. An official report is in preparation by the collab.

Why Study Neutrinos? Neutrinos are half the known stable particles in the universe –       p, e,  Neutrinos are a major component of the universe – ~300 /cm 3, roughly same as CMB photons – nucleons and electrons are ~10 -7 /cm 3 Neutrinos allow for the study of particle physics, without the complications of strong and electromagnetic forces. Svoboda

Neutrino Physics Goals Svoboda

neutrino

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Far Detector Options Water 100 kT fiducial module ft depth. 15% or 30% HQE PMT coverage? Gadolineum or not? 1,2,3 modules? More signal! – Larger volume Liquid Argon 17 kT fiducial module. 300, 800, 4850 ft depth? 3, 4, 5 mm wire spacing? – Probably will be 3 mm photon trigger? 1,2,3 modules? Less background! – Better  0 identification 100 kT water ~= 17 kT liquid Ar for beam physics sensitivity

Far Detector Configurations

Long Baseline Physics: CP violation and neutrino hierarchy

Svoboda300 kT water ~= 50 kT liquid Ar for beam physics sensitivity

LBNE could push to 3-4 x (see talk by Zeller)

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Proton Decay

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Galactic Supernova Burst

Scholberg

Neutrino hierarchy determination from a galactic supernova burst David Webber August 20, 2010

H. Duan and A. Friedland, Neutrino energies at infinity (1 second late-time slice of 10-second burst spectrum)

Consider 3 detector possibilities Water Cherenkov (WC) with 30% phototube coverage and high quantum-efficiency tubes – This is roughly equivalent to Super-K’s coverage WC, 15% coverage, HQE Liquid Argon

reaction cross-sections ns Dominant reaction: WaterArgon Dominant reaction:

Normal Hierarchy: Observed Spectra (accounts for detector acceptance) WC 30% coverage flux at detector WC 15% coverageLiquid Ar

Inverted Hierarchy: Observed Spectra (accounts for detector acceptance) WC 30% coverage flux at detector WC 15% coverageLiquid Ar

How many events are needed to distinguish normal from inverted hierarchy in water? Normal HierarchyInverted Hierarchy 10 2 events indistinguishable Water Detector 30% PMT coverage HQE tubes IBD reaction  2 shown for “wrong” fit 10 5 events clearly distinguishable

How many events for 3 sigma exclusion? Note:    is not the same as Gaussian “3 sigma” = 99.73% confidence 99.73% confidence is… –  2 /NDF of 1.6 for 57 degrees of freedom –  2 /NDF of 1.8 for 34 degrees of freedom

 2 vs. events, WC, 30% coverage Normal hierarchy Inverted hierarchy Normal fitInverted fit Water Detector 30% PMT coverage HQE tubes IBD reaction ~ = events are needed

 2 vs. events, WC, 15% coverage Normal hierarchy Inverted hierarchy Normal fitInverted fit Water Detector 15% PMT coverage HQE tubes IBD reaction ~ = events are needed

How many events are needed to distinguish normal from inverted hierarchy in argon? Normal HierarchyInverted Hierarchy 10 2 events indistinguishable 10 5 events clearly distinguishable Liquid Argon  2 shown for “wrong” fit

 2 vs. events, liquid argon Normal hierarchy Inverted hierarchy Normal fitInverted fit ~ = events are needed

Normal and inverted hierarchy neutrino spectra for 99.7% confidence. Normal HierarchyInverted Hierarchy Liquid Argon 630 events Water Cherenkov 30% PMT coverage 4000 events

Summary WC phototube coverage has little impact on resolving the hierarchy. – 15% is as good as 30% To resolve the hierarchy… – ~4000 events must be observed in water, or – ~630 events must be observed in argon If a SNB occurs at 8.5 kpc… – Need 18.3 kT water – Need 7.6 kT Ar – a 100kT water module would have better statistics than a 17 kT LAr module – The LAr module would show more interesting spectral features Volume estimates based on This study was based on repository revision 754

Confidence vs. Events See other slides SNB Hierarchy study improvements: Allow more parameters to fit in my study to allow for spectral shifts and broadening, eg. E --> E_0 + m*E Perform a multi-module simultaneous for Argon (nue) and Water (nuebar).

LBNE Workshop Summary Choice of far detector is currently undecided – There are many choices Liquid Argon has not been attempted at this size – possibility for something new – technical risk Details of each detector are still under consideration

Far Detector Options Water 100 kT fiducial module ft depth. 15% or 30% HQE PMT coverage? Gadolineum or not? 1,2,3 modules? More signal! – Larger volume Liquid Argon 17 kT fiducial module. 300, 800, 4850 ft depth? 3, 4, 5 mm wire spacing? – Probably will be 3 mm photon trigger? 1,2,3 modules? Less background! – Better  0 identification 100 kT water ~= 17 kT liquid Ar for beam physics sensitivity

References ops/int_10_2b/, Aug ops/int_10_2b/