Nuclear Decay Following Deep Inelastic Scattering of 470 GeV Muons

Abstract

We detected 1 -10 MeV neutrons at laboratory angles from 80 to 140 in coincidence with 470 GeV muons deep inelastically scattered from H, D, C, Ca, and Pb targets. The neutron energy spectrum for Pb can be fitted with two components with temperature parameters of 0.7 and 5.0 MeV. The average neutron multiplicity for 40 ( v~400 GeV is about 5 for Pb, and less than 2 for Ca and C. These data are consistent with a process in which the emitted hadrons do not interact with the rest of the nucleus within distances smaller than the radius of Ca, but do interact within distances on the order of the radius of Pb in the measured kinematic range. For all targets the lack of high nuclear excitation is surprising.PACS numbers: 25.30.MrIn this Letter we present the first measurement of lowenergy neutrons (1 -10 MeV) emitted from a nucleus following deep inelastic scattering (DIS) of a lepton on one of its constituent nucleons. By inferring the excitation energy of the emitting nucleus from these measurements, we provide new information on the response of the nucleus to the momentary color separation that follows DIS. These results are important in understanding a fundamental aspect of QCD, the space-time development of the quark-diquark system resulting from DIS. They are also important for understanding the consequences of quark propagation in nuclear matter in relativistic heavyion reactions.Our present understanding of hadronization, the nonperturbative process by which bare quarks produced in high-energy reactions become hadrons, is largely phenomenological.Several models exist (e.g. , the Lund model [1])which are tuned to the available data and give a good description of the number, flavor, and energy of the created hadrons. However, information on the space-time evolution of hadronization is sparse. Bose-Einstein correlations, which measure coherent effects between identical integral-spin particles, indicate source radii on the order of 2 fm in the rest frame of the source [2]. What is lacking is a clear picture of the distance and time scales required for a bare quark and antiquark, created from the potential 5198 0031-9007/95/74(26)/5198(4)$06. 00

Color Transparency and Hadron Formation Effects in High-Energy Reactions on Nuclei

“…Hadron formation can also be tested by studying the production of low-energy neutrons from the decay of excited nuclear remnant. This has been initiated by the E665 experiment at Fermilab [31], where the neutrons with energy below 10 MeV produced in µ − DIS at 470 GeV off H, D, C, Ca, and Pb targets have been detected. The main motivation was that the nucleus may serve as a "microcalorimeter" for high-energy hadrons: the excitation energy of the residual nucleus grows with the number of holes (wounded nucleons) and can be measured by the number of emitted low-energy neutrons.…”

“…Upper (lower) lines are calculated with (without) adding evaporated neutrons from the nuclear residue. Experimental data are from ref [31]…”

Measurement of the structure function of the nearly free neutron using spectator tagging in inelasticH2(e,e′Tkachenko1, Baillie2, Kuhn3 et al. 2014Phys. Rev. CSelf Cite740390View full textAdd to dashboardCite

“…Frankfurt et al [34] estimated this from the 2 H(e, e p)n break-up reaction at high energies using data on soft neutron production in muon DIS from heavy nuclei [35]. At backward angles FSIs were found to contribute less than 5% to the cross section for p ⊥ s < 100 MeV/c and α s < 1.5.…”

Determination of electron-nucleus collision geometry with forward neutrons

“…There's currently only limited knowledge about the magnitude of this neutron emission for DIS events, the only available measurement being from E665 experiment [30] Fig. 4, one can draw an effective formation length τ 0 = 9 fm/c to consistently describe the magnitude of neutron emission.…”

“…Results of different formation length parameters as a function of ν in the simulation compared with the E665 data[30]. The green line shows the prospective e+Au data kinematics coverage at an EIC.…”