FOOT: a new experiment to measure nuclear fragmentation at intermediate energies

Summary: Charged particle therapy exploits proton or 12C beams to treat deep-seated solid tumors. Due to the advantageous characteristics of charged particles energy deposition in matter, the maximum of the dose is released to the tumor at the end of the beam range, in the Bragg peak region. However, the beam nuclear interactions with the patient tissues induces fragmentation both of projectile and target nuclei and needs to be carefully taken into account. In proton treatments, target fragmentation produces low energy, short range fragments along all the beam range, which deposit a non negligible dose in the entry channel. In 12C treatments the main concern is represented by long range fragments due to beam fragmentation that release their dose in the healthy tissues beyond the tumor. The FOOT experiment (FragmentatiOn Of Target) of INFN is designed to study these processes, in order to improve the nuclear fragmentation description in next generation Treatment Planning Systems and the treatment plans quality. Target (16O and 12C nuclei) fragmentation induced by –proton beams at therapeutic energies will be studied via an inverse kinematic approach, where 16O and 12C therapeutic beams impinge on graphite and hydrocarbon targets to provide the nuclear fragmentation cross section on hydrogen. Projectile fragmentation of 16O and 12C beams will be explored as well. The FOOT detector includes a magnetic spectrometer for the fragments momentum measurement, a plastic scintillator for ΔE and time of flight measurements and a crystal calorimeter to measure the fragments kinetic energy. These measurements will be combined in order to make an accurate fragment charge and isotopic identification. Keywords: Hadrontherapy, Nuclear fragmentation cross sections, Tracking detectors, Scintillating detector

Search for contact interaction, large extra dimensions and finite quark radius in ep collisions at HERA

A search for physics beyond the Standard Model has been performed with high-Q2 neutral current deep inelastic scattering events recorded with the ZEUS detector at HERA. Two data sets, e+p→e +X and e-p→e-X, with respective integrated luminosities of 112 pb-1 and 16 pb-1, were analyzed. The data reach Q2 values as high as 40000 GeV2. No significant deviations from Standard Model predictions were observed. Limits were derived on the effective mass scale in eeqq contact interactions, the ratio of leptoquark mass to the Yukawa coupling for heavy leptoquark models and the mass scale parameter in models with large extra dimensions. The limit on the quark charge radius, in the classical form factor approximation, is 0.85×10 -16 cm. © 2004 Published by Elsevier B.V

SUBSTRUCTURE DEPENDENCE OF JET CROSS SECTIONS AT HERA AND DETERMINATION OF ALPHA(S).

Jet substructure and differential cross sections for jets produced in the photoproduction and deep inelastic ep scattering regimes have been measured with the ZEUS detector at HERA using an integrated luminosity of 82.2 pb−182.2 pb−1. The substructure of jets has been studied in terms of the jet shape and subjet multiplicity for jets with transverse energies View the MathML sourceETjet>17 GeV. The data are well described by the QCD calculations. The jet shape and subjet multiplicity are used to tag gluon- and quark-initiated jets. Jet cross sections as functions of View the MathML sourceETjet, jet pseudorapidity, the jet–jet scattering angle, dijet invariant mass and the fraction of the photon energy carried by the dijet system are presented for gluon- and quark-tagged jets. The data exhibit the behaviour expected from the underlying parton dynamics. A value of αs(MZ)αs(MZ) of View the MathML sourceαs(MZ)=0.1176±0.0009(stat.)−0.0026+0.0009(exp.)−0.0072+0.0091(th.) was extracted from the measurements of jet shapes in deep inelastic scattering

STUDY OF DEEP INELASTIC INCLUSIVE AND DIFFRACTIVE SCATTERING WITH THE ZEUS FORWARD PLUG CALORIMETER

Deep inelastic scattering and its diffractive component, ep→e′γ∗p→e′XNep→e′γ∗p→e′XN, have been studied at HERA with the ZEUS detector using an integrated luminosity of 4.2 pb−14.2 pb−1. The measurement covers a wide range in the γ∗pγ∗p c.m. energy W (37–245 GeV), photon virtuality Q 2 (2.2–80 GeV2) and mass MXMX (0.28–35 GeV). The diffractive cross section for MX>2 GeVMX>2 GeV rises strongly with W ; the rise is steeper with increasing Q 2. The latter observation excludes the description of diffractive deep inelastic scattering in terms of the exchange of a single pomeron. The ratio of diffractive to total cross section is constant as a function of W , in contradiction to the expectation of Regge phenomenology combined with a naive extension of the optical theorem to γ∗pγ∗p scattering. Above MXMX of 8 GeV, the ratio is flat with Q 2, indicating a leading-twist behaviour of the diffractive cross section. The data are also presented in terms of the diffractive structure function, View the MathML sourceF2D(3)(β,xP,Q2), of the proton. For fixed β , the Q 2 dependence of View the MathML sourcexPF2D(3) changes with xPxP in violation of Regge factorisation. For fixed xPxP, View the MathML sourcexPF2D(3) rises as β→0β→0, the rise accelerating with increasing Q2. These positive scaling violations suggest substantial contributions of perturbative effects in the diffractive DIS cross section