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We present a model which describes proton scattering data from ISR to Tevatron energies, and which can be applied to collimation in high energy accelerators, such as the LHC and FCC. Collimators remove beam halo particles, so that they do not impinge on vulnerable regions of the machine, such as the superconducting magnets and the experimental areas. In simulating the effect of the collimator jaws it is crucial to model the scattering of protons at small momentum transfer  t , as these protons can subsequently survive several turns of the ring before being lost. At high energies these soft processes are well described by Pomeron exchange models. We study the behaviour of elastic and single-diffractive dissociation cross sections over a wide range of energy, and show that the model can be used as a global description of the wide variety of high energy elastic and diffractive data presently available. In particular it models low mass diffraction dissociation, where a rich resonance structure is present, and thus predicts the differential and integrated cross sections in the kinematical range appropriate to the LHC. We incorporate the physics of this model into the beam tracking code MERLIN and use it to simulate the resulting loss maps of the beam halo lost in the collimators in the LHC.

In circular particle accelerators, storage rings, or colliders, mitigating beam losses is critical to ensuring optimal performance, particularly for rings that include superconducting magnets. A thorough understanding of beam halo dynamics is essential for this purpose. This paper presents recent results for the measurement of the nonlinear diffusion process of the beam halo at the CERN Large Hadron Collider (LHC). The novel approach used in this paper is based on the analytical framework of the Nekhoroshev theorem, which provides a functional form for the diffusion coefficient. By monitoring the beam loss signal during controlled movements of the collimator jaws, we determine the beam losses at equilibrium for various amplitudes and analyse the beam halo distribution. Postprocessing of these measurements provides the nonlinear diffusion coefficient, which is found to be in excellent agreement with the theoretical assumptions. Measurements from an experiment investigating the effectiveness of beam-beam compensation using beam-beam compensation wires also provide a direct assessment of the compensation’s effectiveness on beam-tail diffusion.

The Large Hadron Collider (LHC) at CERN is a 7 TeV proton synchrotron, with a design stored energy of 362 MJ per beam. The high-luminosity (HL-LHC) upgrade will increase this to 675 MJ per beam. In order to protect the superconducting magnets and other sensitive equipment from quenches and damage due to beam loss, a multilevel collimation system is needed. Detailed simulations are required to understand where particles scattered by the collimators are lost around the ring in a range of machine configurations. merlin++ is a simulation framework that has been extended to include detailed scattering physics, in order to predict local particle loss rates around the LHC ring. We compare merlin++ simulations of losses during the squeeze (the dynamic reduction of theβ function at the interaction points before the beams are put into collision) with loss maps recorded during beam squeezes for run 1 and 2 configurations. The squeeze is particularly important, as both collimator positions and quadrupole magnet currents are changed. We can then predict, using merlin++, the expected losses for the HL-LHC to ensure adequate protection of the machine.

We describe a novel configuration for a neutrino beam line that can simultaneously support both long and short baseline experiments. The neutrino beams originate from pions that are first focused by a magnetic horn, as in a conventional neutrino beam. However, in the case of nuPIL, the horn is followed by a magnetic lattice that is used to select the pion charge and then transports the pions in a production straight. This produces extremely pure neutrino and anti-neutrino beams, while minimizing the amount of beam power that is transported underground for the long-baseline physics program. This configuration greatly simplifies the civil construction leading to a large cost reduction. The principles of the design of nuPIL are presented, together with tracking results and the resulting neutrino flux. The potential of the facility for CP-violation searches, in the framework of the DUNE experiment, is discussed and compared to that of an optimized beam from LBNF.

A measurement of Z → τ ⁺ τ ⁻production cross-section is presented using data, corresponding to an integrated luminosity of 2 fb ⁻¹ , from pp collisions at √s̅=8 TeV collected by the LHCb experiment. The τ ⁺ τ ⁻candidates are reconstructed in final states with the first tau lepton decaying leptonically, and the second decaying either leptonically or to one or three charged hadrons. The production cross-section is measured for Z bosons with invariant mass between 60 and 120 GeV/c ² , which decay to tau leptons with transverse momenta greater than 20 GeV/c and pseudorapidities between 2.0 and 4.5. The cross-section is determined to be σ_(pp)_(→ Z→ τ⁺)_(τ⁻)=95.8 ± 2.1 ± 4.6 ± 0.2 ± 1.1 pb, where the first uncertainty is statistical, the second is systematic, the third is due to the LHC beam energy uncertainty, and the fourth to the integrated luminosity uncertainty. This result is compatible with NNLO Standard model predictions. The ratio of the cross-sections for Z → τ ⁺ τ ⁻to Z → μ ⁺ μ ⁻(Z → e ⁺ e ⁻ ), determined to be 1.01 ± 0.05 (1.02 ± 0.06), is consistent with the lepton-universality hypothesis in Z decays.

A test of lepton universality, performed by measuring the ratio of the branching fractions of the B $^{0}$→ K $^{*0}$μ $^{+}$μ $^{−}$and B $^{0}$→ K $^{*0}$e $^{+}$e $^{−}$decays,$ {R}_{K^{*0}} $, is presented. The K $^{*0}$meson is reconstructed in the final state K $^{+}$π $^{−}$ , which is required to have an invariant mass within 100 MeV/c $^{2}$of the known K $^{*}$ (892) $^{0}$mass. The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of about 3 fb $^{−1}$ , collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The ratio is measured in two regions of the dilepton invariant mass squared, q $^{2}$ , to be$ {R}_{K^{*0}}=\\left\\{\\begin{array}{l}{0.66_{-}^{+}}_{0.07}^{0.11}\\left(\\mathrm{stat}\\right)\\pm 0.03\\left(\\mathrm{syst}\\right)\\kern1em \\mathrm{f}\\mathrm{o}\\mathrm{r}\\kern1em 0.045<{q}^2<1.1\\kern0.5em {\\mathrm{GeV}}^2/{c}^4,\\hfill \\\ {}{0.69_{-}^{+}}_{0.07}^{0.11}\\left(\\mathrm{stat}\\right)\\pm 0.05\\left(\\mathrm{syst}\\right)\\kern1em \\mathrm{f}\\mathrm{o}\\mathrm{r}\\kern1em 1.1<{q}^2<6.0\\kern0.5em {\\mathrm{GeV}}^2/{c}^4.\\hfill \\end{array}\\right. $

Bose-Einstein correlations of same-sign charged pions, produced in proton-proton collisions at a 7 TeV centre-of-mass energy, are studied using a data sample collected by the LHCb experiment. The signature for Bose-Einstein correlations is observed in the form of an enhancement of pairs of like-sign charged pions with small four-momentum difference squared. The charged-particle multiplicity dependence of the Bose-Einstein correlation parameters describing the correlation strength and the size of the emitting source is investigated, determining both the correlation radius and the chaoticity parameter. The measured correlation radius is found to increase as a function of increasing charged-particle multiplicity, while the chaoticity parameter is seen to decrease.

A mail survey was undertaken in 1991 to obtain information on beginning weed science courses being taught in the United States and Canada. Out of 74 questionnaires sent to 44 states and 7 provinces, there were 54 responses of which 49 institutions had a beginning weed science course. The responses showed that these courses are taught primarily once a year (88%) in the fall term (77%). Most schools are under the semester system (82%) with the credits arranged so that there are about 30 hours of lecture per term with a one-credit laboratory. The students in beginning weed science courses are mostly seniors (47%) and juniors (34%) and are primarily from Agronomy, Plant Science, or Crop Science departments (46%) and Horticulture (23%). The average time spent on different topics agreed well with the priorities and are listed in the text. The survey also gathered data on weed identification requirements, special requirements of individual courses, evaluation of students, additional comments by instructors, and special teaching guides or techniques that instructors are willing to share with others.