Experimental evidence of independence of nuclear de-channeling length on the particle charge sign

Abstract

Under coherent interactions, particles undergo correlated collisions with the crystal lattice and their motion result in confinement in the fields of atomic planes, i.e. particle channeling. Other than coherently interacting with the lattice, particles also suffer incoherent interactions with individual nuclei and may leave their bounded motion, i.e., they de-channel. The latter is the main limiting factor for applications of coherent interactions in crystal-assisted particle steering. We experimentally investigated the nature of dechanneling of 120 GeV/c e − and e + in a bent silicon crystal at H4-SPS external line at CERN. We found that while channeling efficiency differs significantly for e − (2 ± 2%) and e + (54 ± 2%), their nuclear de-channeling length is comparable, (0.6 ± 0.1) mm for e − and (0.7 ± 0.3) mm for e + . The experimental proof of the equality of the nuclear dechanneling length for positrons and electrons is interpreted in terms of similar dynamics undergone by the channeled particles in the field of nuclei irrespective of their charge.In the last decade, a significant boost to the research on particle-crystal interactions was provided by the fabrication of uniformly bent crystals [1] with thickness along the beam suitable for experiments at high-energy [2,3]. Measurements proved the capability of channeling for manipulation of positively [4] and negatively [5,6] charged particle beams from MeV [7] up to hundreds of GeV [8,9], and for the generation of intense electromagnetic radiation from sub-GeV [10,11] to hundreds-GeV electron beams [12]. Moreover, channeling effects were exploited for steering [13]

Bent crystals for efficient beam steering of multi TeV-particle beams

“…New coherent interaction effects of ultra-relativistic proton beams with crystals were observed, among which were the phenomena of volume reflection [ 27 , 28 ], beam steering by means of crystal axes [ 29 – 31 ], multiple volume reflection [ 32 – 35 ] and mirroring [ 36 ]. For the first time, efficient beam steering was also recorded for both positively [ 37 – 39 ] and negatively charged particle beams [ 40 , 41 ].…”

Pseudoscalar pole contribution to the hadronic light-by-light piece of aμ

“…3) 5 This interaction term is the only single-trace operator O(m 2 P ) from those given in [24]. 6 This term generates a mass spliting effect in the nonet of resonances, inducing an explicit U(3) breaking effect. As a result, the masses of the vector resonances are given by…”

“…The produced τ's would cross the pipe and enter a crystal where a sufficiently large electromagnetic field can be obtained, due to the potential between crystalographic planes of a bent crystal, to give the precession of the lepton [5]. More details on the experimental arrange are given in [6].…”

Investigation on steering of ultrarelativistic $e^{\pm}$ beam through an axially oriented bent crystal

“…In this paper, we present an investigation through experiments, analytical estimations, and Monte Carlo simulations on the axial deflection of e ± beams in bent crystals and its dependence on crystal curvature and choice of crystal axis and bending planes. This is indeed the first experimental evidence of axial stochastic deflection of ultrarelativistic leptons in bent crystals, since only planar channeling and volume reflection were investigated for high-energy electrons and positrons [22][23][24][25][26][27][28][29][30]. With this work, we also addressed possible schemes for manipulation of e ± beams, such as steering or extraction, in present and future electron/positron (and in general lepton) accelerators and colliders.…”