Beam losses from ultra-peripheral nuclear collisions between Pb ions in the Large Hadron Collider and their alleviation

Electromagnetic interactions between colliding heavy ions at the Large Hadron Collider (LHC) at CERN will give rise to localized beam losses that may quench superconducting magnets, apart from contributing significantly to the luminosity decay. To quantify their impact on the operation of the collider, we have used a three-step simulation approach, which consists of optical tracking, a Monte-Carlo shower simulation and a thermal network model of the heat flow inside a magnet. We present simulation results for the case of Pb ion operation in the LHC, with focus on the ALICE interaction region, and show that the expected heat load during nominal Pb operation is 40% above the quench level. This limits the maximum achievable luminosity. Furthermore, we discuss methods of monitoring the losses and possible ways to alleviate their effect.Comment: 17 pages, 20 figure

Initial evidence for the criterion-related and structural validity of the long versions of the direct and meta-perspectives of the Coach-Athlete Relationship Questionnaire

This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2010 Taylor & Francis.The aim of the present study was to develop and initially validate a longer version of the direct (Jowett & Ntoumanis, 2004) and meta-perspectives (Jowett, 2009a, 2009b) of the Coach-Athlete Relationship Questionnaire (CART-Q). In Study 1, instruments (e.g. questionnaires, scales, and inventories) that have been used to assess relationship quality in the broader psychological literature were examined and items potentially relevant to the coach-athlete relationship were identified. The content validity of the identified items was then assessed using expert panels. A final questionnaire was subsequently prepared and administered to 693 participants (310 coaches and 383 athletes). Confirmatory factor analysis was employed to assess the multidimensional nature of the questionnaire based on the 3Cs (i.e. closeness, commitment, and complementarity) model of the coach-athlete relationship. The findings indicated that the direct and meta-perspective items of the long versions of the CART-Q approached an adequate data fit. Moreover, evidence for the internal consistency and criterion validity of the new instruments was also obtained. In Study 2, the newly developed measure was administered to an independent sample of 251 individuals (145 athletes and 106 coaches). Further statistical support was gained for the factorial validity and reliability of the longer version of the CART-Q

Physics Opportunities with the FCC-hh Injectors

In this chapter we explore a few examples of physics opportunities using the existing chain of accelerators at CERN, including potential upgrades. In this context the LHC ring is also considered as a part of the injector system. The objective is to find examples that constitute sensitive probes of New Physics that ideally cannot be done elsewhere or can be done significantly better at theCERN accelerator complex. Some of these physics opportunities may require a more flexible injector complex with additional functionality than that just needed to inject protons into the FCC-hh at the right energy, intensity and bunch structure. Therefore it is timely to discuss these options concurrently with the conceptual design of the FCC-hh injector system.Comment: 13 pages, chapter 5 in Physics at the FCC-hh, a 100 TeV pp collide

Design of beam optics for the Future Circular Collider e+e- -collider rings

A beam optics scheme has been designed for the Future Circular Collider-e+e- (FCC-ee). The main characteristics of the design are: beam energy 45 to 175 GeV, 100 km circumference with two interaction points (IPs) per ring, horizontal crossing angle of 30 mrad at the IP and the crab-waist scheme [1] with local chromaticity correction. The crab-waist scheme is implemented within the local chromaticity correction system without additional sextupoles, by reducing the strength of one of the two sextupoles for vertical chromatic correction at each side of the IP. So-called "tapering" of the magnets is applied, which scales all fields of the magnets according to the local beam energy to compensate for the effect of synchrotron radiation (SR) loss along the ring. An asymmetric layout near the interaction region reduces the critical energy of SR photons on the incoming side of the IP to values below 100 keV, while matching the geometry to the beam line of the FCC proton collider (FCC-hh) [2] as closely as possible. Sufficient transverse/longitudinal dynamic aperture (DA) has been obtained, including major dynamical effects, to assure an adequate beam lifetime in the presence of beamstrahlung and top-up injection. In particular, a momentum acceptance larger than +/-2% has been obtained, which is better than the momentum acceptance of typical collider rings by about a factor of 2. The effects of the detector solenoids including their compensation elements are taken into account as well as synchrotron radiation in all magnets. The optics presented in this paper is a step toward a full conceptual design for the collider. A number of issues have been identified for further study

Measurements of heavy ion beam losses from collimation

The collimation efficiency for Pb ion beams in the LHC is predicted to be lower than requirements. Nuclear fragmentation and electromagnetic dissociation in the primary collimators create fragments with a wide range of Z/A ratios, which are not intercepted by the secondary collimators but lost where the dispersion has grown sufficiently large. In this article we present measurements and simulations of loss patterns generated by a prototype LHC collimator in the CERN SPS. Measurements were performed at two different energies and angles of the collimator. We also compare with proton loss maps and find a qualitative difference between Pb ions and protons, with the maximum loss rate observed at different places in the ring. This behavior was predicted by simulations and provides a valuable benchmark of our understanding of ion beam losses caused by collimation.Comment: 12 pages, 20 figure

A Storage Ring based Option for the LHeC

The LHeC aims at the generation of hadron-lepton collisions with center of mass energies in the TeV scale and luminosities of the order of $10^{32}-10^{33} cm^{-2} sec^{-1}$ by taking advantage of the existing LHC 7 TeV proton ring and adding a high energy electron accelerator. This paper presents technical considerations and potential parameter choices for such a machine and outlines some of the challenges arising when an electron storage ring based option, constructed within the existing infrastructure of the LHC, is chosen

Keele Aches and Pains Study Protocol: validity, acceptability and feasibility of the Keele STarT MSK Tool for subgrouping musculoskeletal patients in primary care

Musculoskeletal conditions represent a considerable burden worldwide, and are predominantly managed in primary care. Evidence suggests that many musculoskeletal conditions share similar prognostic factors. Systematically assessing patient’s prognosis, and matching treatments based on prognostic subgroups (stratified care), has been shown to be clinically and cost effective. This study (Keele Aches and Pains Study: KAPS) aims to refine and examine the validity of a brief questionnaire (Keele STarT MSK Tool), designed to enable risk-stratification of primary care patients with the five most common musculoskeletal pain presentations. We will also describe the subgroups of patients, and explore the acceptability and feasibility of using the tool, and how the tool is best implemented in clinical practice. The study design is mixed methods: a prospective, quantitative observational cohort study with a linked qualitative focus group and interview study. Patients who have consulted their General Practitioner or Healthcare Practitioner (GP/HCP) about a relevant musculoskeletal condition will be recruited from General practice. Participating patients will complete a baseline questionnaire (shortly after consultation), plus questionnaires 2 and 6 months later. A sub-sample of patients, along with participating GPs and HCPs, will be invited to take part in qualitative focus groups and interviews. The Keele STarT MSK Tool will be refined based on face, discriminant, construct and predictive validity at baseline and 2 months, and validated using data from 6 month follow-up. Patient and clinician perspectives about using the tool will be explored. This study will provide a validated prognostic tool (the Keele STarT MSK Tool) with established cut-points to stratify patients with the five most common musculoskeletal presentations into low, medium and high risk subgroups. The qualitative analysis of patient and healthcare perspectives will inform how to embed the tool into clinical practice using established general practice IT systems and clinician support packages

Stratified care versus usual care for management of patients presenting with sciatica in primary care (SCOPiC): a randomised controlled trial

Background Sciatica has a substantial impact on individuals and society. Stratified care has been shown to lead to better outcomes among patients with non-specific low back pain, but it has not been tested for sciatica. We aimed to investigate the clinical and cost-effectiveness of stratified care versus non-stratified usual care for patients presenting with sciatica in primary care. Methods We did a two-parallel arm, pragmatic, randomised controlled trial across three centres in the UK (North Staffordshire, North Shropshire/Wales, and Cheshire). Eligible patients were aged 18 years or older, had a clinical diagnosis of sciatica, access to a mobile phone or landline number, were not pregnant, were not currently receiving treatment for the same problem, and had no previous spinal surgery. Patients were recruited from general practices and randomly assigned (1:1) by a remote web-based service to stratified care or usual care, stratified by centre and stratification group allocation. In the stratified care arm, a combination of prognostic and clinical criteria associated with referral to spinal specialist services were used to allocate patients to one of three groups for matched care pathways. Group 1 was offered brief advice and support in up to two physiotherapy sessions; group 2 was offered up to six physiotherapy sessions; and group 3 was fast-tracked to MRI and spinal specialist assessment within 4 weeks of randomisation. The primary outcome was self-reported time to first resolution of sciatica symptoms, defined as “completely recovered” or “much better” on a 6-point ordinal scale, collected via text messages or telephone calls. Analyses were by intention to treat. Health-care costs and cost-effectiveness were also assessed. This trial is registered on the ISRCTN registry, ISRCTN75449581. Findings Between May 28, 2015, and July 18, 2017, 476 patients from 42 general practices around three UK centres were randomly assigned to stratified care or usual care (238 in each arm). For the primary outcome, the overall response rate was 89% (9467 of 10 601 text messages sent; 4688 [88%] of 5310 in the stratified care arm and 4779 [90%] of 5291 in the usual care arm). Median time to symptom resolution was 10 weeks (95% CI 6·4–13·6) in the stratified care arm and 12 weeks (9·4–14·6) in the usual care arm, with the survival analysis showing no significant difference between the arms (hazard ratio 1·14 [95% CI 0·89–1·46]). Stratified care was not cost-effective compared to usual care. Interpretation The stratified care model for patients with sciatica consulting in primary care was not better than usual care for either clinical or health economic outcomes. These results do not support a transition to this stratified care model for patients with sciatica