Abstract
Cross section data from the HARP experiment for pion production by protons from a tantalum target have been convoluted with the acceptance of the front-end channel for the proposed neutrino factory or muon collider and integrated over the full phase space measured by HARP, to determine the beam-energy dependence of the muon yield. This permits a determination of the optimal beam energy for the proton driver for these projects. The cross section data are corrected for the beam-energy dependent amplification due to the development of hadronic showers in a thick target. The conclusion is that, for constant beam power, the yield is maximum for a beam energy of about 7 GeV, but it is within 10% of this maximum for $4<{T}_{\mathrm{beam}}<11\text{ }\text{ }\mathrm{GeV}$, and within 20% of the maximum for ${T}_{\mathrm{beam}}$ as low as 2 GeV. This result is insensitive to which of the two HARP groups' results are used, and to which pion generator is used to compute the thick target effects.
Highlights
One of the important design parameters of a possible future neutrino factory (NF) or muon collider (MC) is the energy of the high-power proton accelerator that will be used to produce the pions, whose decay muons will be captured, cooled, and stored in a storage ring, either to produce intense neutrino beams or to provide þÀ collisions
The acceptance is convoluted with the measured double-differential cross section of pion production from a tantalum target, which is close in atomic weight to mercury, the favored target material for the NF/MC projects [1]
The beam energy of the proton driver for a neutrino factory or muon collider is an important design parameter, which can be chosen based on experimental data from the HARP experiment
Summary
One of the important design parameters of a possible future neutrino factory (NF) or muon collider (MC) is the energy of the high-power proton accelerator that will be used to produce the pions, whose decay muons will be captured, cooled, and stored in a storage ring, either to produce intense neutrino beams or to provide þÀ collisions. The study of the yield of captured muons as a function of proton beam energy has had to rely on simulations [1,2], since data on pion production cross sections over the relevant phase space has been quite sparse. The acceptance is defined to be the number of muons (or pions), as a fraction of the number of pions produced at the target, that reach the end of the 50-m long tapered solenoid channel It is computed in terms of the momentum and angle, p and , of the pions leaving the target. The acceptance-weighted cross section is integrated over the measured phase space, and divided by the beam kinetic energy, to give a value proportional to the muon yield normalized to constant proton beam power. The beampower normalized muon yield is presented as a function of incident proton kinetic energy between 2.2 and 11.1 GeV (3 p 12 GeV=c), which brackets the beam energies under consideration for high-power proton sources at Fermilab [6] and CERN [7]
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