How Many Muons Do We Need to Store in a Ring For Neutrino Cross-Section Measurements?

Geer, Steve

Fermi National Accelerator Laboratory

关键词: Pions;    Decay;    Spectra;    Energy Range;    Neutrino Oscillation;   

DOI  :  10.2172/1022119
RP-ID  :  FERMILAB-FN-0924-APC
RP-ID  :  AC02-07CH11359
RP-ID  :  1022119

美国|英语

来源: UNT Digital Library

【 摘 要 】

Analytical estimate of the number of muons that must decay in the straight section of a storage ring to produce a neutrino & anti-neutrino beam of sufficient intensity to facilitate cross-section measurements with a statistical precision of 1%. As we move into the era of precision long-baseline {nu}{sub {mu}} {yields} {nu}{sub e} and {bar {nu}}{sub {mu}} {yields} {bar {nu}}{sub e} measurements there is a growing need to precisely determine the {nu}{sub e} and {bar {nu}}{sub e} cross-sections in the relevant energy range, from a fraction of 1 GeV to a few GeV. This will require {nu}{sub e} and {bar {nu}}{sub e} beams with precisely known fluxes and spectra. One way to produce these beams is to use a storage ring with long straight sections in which muon decays ({mu}{sup -} {yields} e{sup -}{nu}{sub {mu}}{bar {nu}}{sub e} if negative muons are stored, and {nu}{sup +} {yields} e{sup +}{nu}{sub e}{bar {nu}}{sub {mu}} if positive muons are stored) produce the desired beam. The challenge is to capture enough muons in the ring to obtain useful neutrino and anti-neutrino fluxes. Early proposals to use a muon storage ring for neutrino oscillation experiments were based upon injecting 'high energy' charged pions into the ring which then decayed to create stored muons. These proposals were hampered by lack of sufficient intensity to pursue the physics. The Neutrino Factory proposal in 1997 was designed to fix this problem by using a Muon Collider class 'low energy' muon source to capture many more pions at low energy, allow them to decay in an external decay channel, manipulate their phase space to capture as many muons as possible within the acceptance of an accelerator, and then accelerate to the energy of choice before injecting into a specially designed ring with long straight sections. All this technology would do a wonderful job in fixing the intensity problem, but at a price that excludes this solution from being realized in the short term. The question that we are now faced with is whether the older, lower intensity 'parasitic' muon storage ring based on 'high energy' pion decays can, with suitable modification, produce sufficient intensity to measure the desired cross-sections. Fortunately, the intensity requirements for cross-section measurements are less demanding than the corresponding requirements for oscillation measurements, so there is hope. To fuel the discussion, in this note we consider the design goal: how many muons do we need to store?