Study of Low-energy Neutrino Factory at the Fermilab to DUSEL Baseline PDF Download

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This note constitutes a Letter of Interest to study the physics capabilities of, and to develop an implementation plan for, a neutrino physics program based on a Low-Energy Neutrino Factory at Fermilab providing a? beam to a detector at the Deep Underground Science and Engineering Laboratory. It has been over ten years since the discovery of neutrino oscillations [1] established the existence of neutrino masses and leptonic mixing. Neutrino oscillations thus provide the first evidence of particle physics beyond the Standard Model. Most of the present neutrino oscillation data are well described by the 3? mixing model. While a number of the parameters in this model have already been measured, there are several key parameters that are still unknown, namely, the absolute neutrino mass scale, the precise value of the mixing angles, the CP phase? and hence the presence or absence of observable CP-violation in the neutrino sector. Future measurements of these parameters are crucial to advance our understanding of the origin of neutrino masses and of the nature of flavor in the lepton sector. The ultimate goal of a program to study neutrino oscillations goes beyond a first measurement of parameters, and includes a systematic search for clues about the underlying physics responsible for the tiny neutrino masses, and, hopefully, the origin of the observed flavor structure in the Standard Model, as well as the possible source of the observed matter-antimatter asymmetry in the Universe. To achieve this goal will almost certainly require precision measurements that go well beyond the presently foreseen program. One of the most promising experimental approaches to achieve some of the goals mentioned above is to build a Neutrino Factory and its corresponding detector. The Neutrino Factory produces neutrino beams from muons which have been accelerated to an energy of, for example, 25 GeV. The muons are stored in a race-track shaped decay ring and then decay along the straight sections of the ring. Since the decay of the muon is well understood, the systematic uncertainties associated with a neutrino beam produced in this manner are very small. Beam diagnostics in the decay ring and a specially designed near detector further reduce the systematic uncertainties of the neutrino beam produced at the Neutrino Factory. In addition since the muon (anti-muon) decays produce both muon and anti-electron neutrinos (anti-muon and electron neutrinos), many oscillation channels are accessible from a Neutrino Factory, further extending the reach in the oscillation parameter space. Over the last decade there have been a number of studies [2-5] that have explored the discovery reach of Neutrino Factories in the small mixing angle,?13, and its capability to determine the mass hierarchy and determine if CP is violated in leptons through observation of phase parameter,?. The most recent study to be completed [6], the International scoping study of a future Neutrino Factory and super-beam facility (the ISS), studied the physics capabilities of various future neutrino facilities: super-beam,?-Beam and Neutrino Factory and has determined that the Neutrino Factory with an energy of H"5 GeV has the best discovery reach for small values of sin22?13, reaching an ultimate sensitivity of between 10−5 and 10−4. However, for larger values of sin22?13 (> 10−3), the sensitivity of other experimental approaches is competitive to that of the 25 GeV Neutrino Factory. The wide-band neutrino beam (WBB) produced at Fermilab and directed towards DUSEL [7] is one such competitor. For the case where sin22?13 (> 10−3) is large, initial studies have shown that a Low-Energy Neutrino Factory [8-10] with an energy of, for example, 4 GeV, may be both cost-effective and offers exquisite sensitivity. The required baseline for a Low-Energy Neutrino Factory matches Fermilab to DUSEL and, therefore, its physics potential and implementation should be studied in the context of DUSEL along with those for the WBB.