Determining the inelastic proton–proton cross section at the large hadron collider using minimum bias events

In this paper a new method is described for determining the non-diffractive part of the inelastic proton–proton cross section, at the LHC centre of mass energy of 14 TeV. The method is based on counting the number of inelastic proton–proton interactions in the collision regions. According to a preliminary investigation, this measurement will be best suited for the initial low luminosity phase of the LHC. Knowledge of the proton–proton luminosity is likely to dominate the measurement uncertainty. PACS 13.85.Hd     

Higgs and Z<Superscript>′</Superscript> phenomenology in B–L extension of the standard model at LHC

The phenomenology of the low scale U(1)_B–L extension of the standard model and its implications at LHC energies is presented. In this model, an extra gauge boson corresponding to B–L gauge symmetry and an extra SM singlet scalar (heavy Higgs boson) are predicted. We show a detailed analysis of both heavy and light Higgs bosons decay and production in addition to the possible decay channels of the new gauge boson. We find that the cross sections of the SM-like Higgs production are reduced by ∼20–30%, while its decay branching ratios remain intact. The extra Higgs boson has relatively small cross sections and the branching ratios of Z^′→l⁺l^- are of order ∼20% to be compared to ∼3% of the SM results. Hence, the search for Z^′ is accessible via a clean dilepton signal at LHC.     

From the LHC to future colliders

Discoveries at the LHC will soon set the physics agenda for future colliders. This report of a CERN Theory Institute includes the summaries of Working Groups that reviewed the physics goals and prospects of LHC running with 10 to 300 fb^?1 of integrated luminosity, of the proposed sLHC luminosity upgrade, of the ILC, of CLIC, of the LHeC and of a muon collider. The four Working Groups considered possible scenarios for the first 10 fb^?1 of data at the LHC in which (i) a state with properties that are compatible with a Higgs boson is discovered, (ii) no such state is discovered either because the Higgs properties are such that it is difficult to detect or because no Higgs boson exists, (iii) a missing-energy signal beyond the Standard Model is discovered as in some supersymmetric models, and (iv) some other exotic signature of new physics is discovered. In the contexts of these scenarios, the Working Groups reviewed the capabilities of the future colliders to study in more detail whatever new physics may be discovered by the LHC. Their reports provide the particle physics community with some tools for reviewing the scientific priorities for future colliders after the LHC produces its first harvest of new physics from multi-TeV collisions.     

MSSM Higgs boson searches at the Tevatron and the LHC: Impact of different benchmark scenarios

The Higgs boson search has shifted from LEP2 to the Tevatron and will subsequently move to the LHC. The current limits from the Tevatron and the prospective sensitivities at the LHC are often interpreted in specific MSSM scenarios. For heavy Higgs boson production and subsequent decay into or τ⁺τ^–, the present Tevatron data allow one to set limits in the M_A–tan β plane for small M_A and large tan β values. Similar channels have been explored for the LHC, where the discovery reach extends to higher values of M_A and smaller tan β. Searches for MSSM charged Higgs bosons, produced in top decays or in association with top quarks, have also been investigated at the Tevatron and the LHC. We analyze the current Tevatron limits and prospective LHC sensitivities. We discuss how robust they are with respect to variations of the other MSSM parameters and possible improvements of the theoretical predictions for Higgs boson production and decay. It is shown that the inclusion of supersymmetric radiative corrections to the production cross sections and decay widths leads to important modifications of the present limits on the MSSM parameter space. The impact on the region where only the lightest MSSM Higgs boson can be detected at the LHC is also analyzed. We propose to extend the existing benchmark scenarios by including additional values of the higgsino mass parameter μ. This affects only slightly the search channels for a SM-like Higgs boson, while having a major impact on the searches for non-standard MSSM Higgs bosons.     

The wily colonial boy

We review here the prospects of a long-term upgrade programme for the Large Hadron Collider (LHC), CERN laboratory's new proton–proton collider. The super-LHC, which is currently under evaluation and design, is expected to deliver of the order of ten times the statistics of the LHC. In addition to a non-technical summary of the principal physics arguments for the upgrade, I present a pedagogical introduction to the technological challenges on the accelerator and experimental fronts, and a review of the current status of the planning.     

Unitarity bounds for gauged axionic interactions and the Green–Schwarz mechanism

We analyze the effective actions of anomalous models in which a four-dimensional version of the Green–Schwarz mechanism is invoked for the cancellation of the anomalies, and we compare it with those models in which gauge invariance is restored by the presence of a Wess–Zumino term. Some issues concerning an apparent violation of unitarity of the mechanism, which requires Dolgov–Zakharov poles, are carefully examined, using a class of amplitudes studied in the past by Bouchiat–Iliopoulos–Meyer (BIM), and elaborating on previous studies. In the Wess–Zumino case we determine explicitly the unitarity bound using a realistic model of intersecting branes (the Madrid model) by studying the corresponding BIM amplitudes. This is shown to depend significantly on the Stückelberg mass and on the coupling of the extra anomalous gauge bosons and allows one to identify standard-model-like regions (which are anomaly-free) from regions where the growth of certain amplitudes is dominated by the anomaly, separated by an inflection point, which could be studied at the LHC. The bound can even be around 5–10 TeV for a Z’ mass around 1 TeV and varies sensitively with the anomalous coupling. The results for the WZ case are quite general and apply to all the models in which an axion-like interaction is introduced as a generalization of the Peccei–Quinn mechanism, with a gauged axion.     

The upgrade of endcap CMS muon system

The configuration and composition of the CMS muon system are presented. The paper is focused on cathode strip chambers (CSC) used as the endcap muon system detectors. The goals and objectives of the endcap muon system upgrade are formulated. The main results of works accomplished for the ME1/1 CSCs upgrade and the new ME4/2 muon station construction during the LHC Long Shutdown-1 (2013–2014) are presented. The improved performances of the endcap muon system are shown using experimental data obtained after the upgrade (Run2 data).     

Micromegas chambers for the experiment ATLAS at the LHC (A Brief Overview)

The increase in luminosity and energy of the Large hadron collider (LHC) in the next upgrade (Phase-1) in 2018–2019 will lead to a significant increase in radiation load on the ATLAS detector, primarily in the areas close to the interaction point of the LHC proton beams. One of these regions is the Small Wheel of the ATLAS Muon Spectrometer. It is planned to be replaced with the New Small Wheel that will have Micromegas chambers as main coordinate detectors. The paper gives an overview of all existing types of Micromegas detectors with special focus on the Micromegas chambers for the ATLAS detector upgrade.     

Probe of the Wtb coupling in t \bar{t} pair production at linear colliders

The Wtb vertex can be probed on future colliders in the processes of single top production (LHC, pp mode, NLC, mode) and of top pair production (NLC, mode). We analyze observables sensitive to anomalous Wtb couplings in the top pair production process of collisions. In particular, forward–backward and spin–spin asymmetries of the top decay products and the asymmetry of the lepton energy spectrum are considered. Possible bounds on anomalous couplings obtained are competitive to those expected from the upgraded Tevatron and LHC. The validity of the infinitely small width approximation for the three-body top decay is also studied in detail. Received: 20 January 2000 / Revised version: 12 April 2000 / Published online: 18 May 2000     

Search for heavy neutral MSSM Higgs bosons with CMS: reach and Higgs mass precision

The search for MSSM Higgs bosons will be an important goal at the LHC. We analyze the search reach of the CMS experiment for the heavy neutral MSSM Higgs bosons with an integrated luminosity of 30 or 60 fb^-1. This is done by combining the latest results for the CMS experimental sensitivities based on full simulation studies with state-of-the-art theoretical predictions of the MSSM Higgs-boson properties. The results are interpreted in MSSM benchmark scenarios in terms of the parameters tan β and the Higgs-boson mass scale, M_A. We study the dependence of the 5σ discovery contours in the M_A–tan β plane on variations of the other supersymmetric parameters. The largest effects arise from a change in the higgsino mass parameter μ, which enters both via higher-order radiative corrections and via the kinematics of Higgs decays into supersymmetric particles. While the variation of μ can shift the prospective discovery reach (and correspondingly the ”LHC wedge” region) by about Δtan β=10, we find that the discovery reach is rather stable with respect to the impact of other supersymmetric parameters. Within the discovery region we analyze the accuracy with which the masses of the heavy neutral Higgs bosons can be determined. We find that an accuracy of 1–4% should be achievable, which could make it possible in favorable regions of the MSSM parameter space to experimentally resolve the signals of the two heavy MSSM Higgs bosons at the LHC.     

Pair production of charged Higgs bosons in the left–right twin Higgs model at the ILC and LHC

The left–right twin Higgs (LRTH) model predicts the existence of a pair of charged Higgs bosons φ^±. In this paper, we study the production of the charged Higgs boson pair φ^± at the international linear collider (ILC) and the CERN large hadron collider (LHC). The numerical results show that the production rates are at the level of several tens fb at the ILC, and the process e⁺e^-→φ⁺φ^- can produce adequately distinct multi-jet final states. We also discuss the charged Higgs boson pair production via the process qq̄→φ⁺φ^- at the LHC and estimate in this case the production rates. We find that, as long as the charged Higgs bosons are not too heavy, they can be abundantly produced at the LHC. The possible signatures of these new particles might be detected at the ILC and LHC experiments. PACS 12.60.Fr; 14.80.Mz; 14.65.Ha; 12.15.Lk     

Soft diffraction at the LHC: a partonic interpretation

We present a ‘new generation’ model for high energy proton–proton ‘soft’ interactions. It allows for a full set of multipomeron vertices as well as for including multichannel eikonal scattering. It describes the behaviour of the proton–proton total, σ_tot, and elastic, dσ_el/dt, cross sections together with those for low- and high-mass proton dissociation. Although the model contains a comprehensive set of multipomeron diagrams, it has a simple partonic interpretation. Including the more complicated multipomeron vertices reduces the absorptive effects as compared to the predictions in which only the triple-pomeron vertex is considered. Tuning the model to describe the available ‘soft’ data in the CERN ISR–tevatron energy range, we predict the total, elastic, single- and double-diffractive dissociation cross sections at the LHC energy. An inescapable consequence of including multichannel eikonal and multipomeron effects is that the total cross section is expected to be lower than before: indeed, we find σ_tot≃ 90 mb at the LHC energy. We also present differential forms of the cross sections. In addition, we calculate soft diffractive central production.     

Eikonal regime of gravity-induced scattering at higher energy proton colliders

We compute transplanckian parton scattering in flat extra-dimensional theories at the LHC and at the recently discussed high-energy upgrade (HE LHC). We report new leading-order calculations of the QCD background. We apply appropriate cuts to satisfy the necessary conditions for the eikonal approximation to be valid while at the same time maximising the signal to background ratio at LHC energies. We study the computability of the eikonal signal and consider the effect of a possible 33 TeV high-energy upgrade to the LHC, which serves to extend the calculable region and to enhance the signal to background ratio.     

Investigation of the ALICE muon forward spectrometer performances for upsilon measurement

ALICE (A Large Ion Collider Experiment) is the LHC detector dedicated to the study of nucleus–nucleus collisions, in which the formation of the quark–gluon plasma (QGP) is expected. Heavy quarkonia, especially the Upsilon states, are relevant for studying the QGP since they provide an essential probe of the earliest and hottest stages of heavy ion collisions. They will be measured via their dimuon decay channel in ALICE in the muon spectrometer. The muon spectrometer performance has been studied in simulations, the results will be presented with emphasis on the trigger efficiency and rate in Pb–Pb collisions. The expected yields of Upsilon states will be extracted from a simulation based on a global fit of the dimuon mass spectra for different collision centralities.     

A fast muon trigger for the PHENIX forward spectrometer upgrade

The PHENIX forward upgrade adds nosecone calorimeters and level-1 trigger (LVL-1) detectors to the muon forward spectrometers. The muon detector will trigger on high pT muons from W decay and reject background. This will enable study of quark and anti-quark polarizations in the proton. The upgrade will add momentum and timing information to the present muon trigger. Signals from 3 Resistive Plate Chambers (RPCs) will provide momentum and timing information for the LVL-1 trigger. Each RPC carries a plane with coarse structure to establish a space point for timing and one with radial cathode strips for azimuthal resolution. Timing resolution of ≈ 2 ns rejects beam-related backgrounds and tracking from RPCs minimizes muons from hadron decays. RPC information is sent by optical. bers to LVL-1 trigger processors. A discussion of physics measurements possible, layout of the upgrade and details of RPC design and tests are given below. for the PHENIX collaboration Presented in the Poster Session “Future Experiments and Facilities” at the 18th International Conference “Quark Matter 2005”, Budapest, Hungary, 4–9 August 2005.     

Multiplicity studies and effective energy in ALICE at the LHC

In this work we explore the possibility to perform “effective energy” studies in very high energy collisions at the CERN large hadron collider (LHC). In particular, we focus on the possibility to measure in pp collisions the average charged multiplicity as a function of the effective energy with the ALICE experiment, using its capability to measure the energy of the leading baryons with the zero degree calorimeters. Analyses of this kind have been done at lower centre-of-mass energies and have shown that, once the appropriate kinematic variables are chosen, particle production is characterized by universal properties: no matter the nature of the interacting particles, the final states have identical features. Assuming that this universality picture can be extended to ion–ion collisions, as suggested by recent results from RHIC experiments, a novel approach based on the scaling hypothesis for limiting fragmentation has been used to derive the expected charged event multiplicity in AA interactions at LHC. This leads to scenarios where the multiplicity is significantly lower compared to most of the predictions from the models currently used to describe high energy AA collisions. A mean charged multiplicity of about 1000–2000 per rapidity unit (at η∼0) is expected for the most central Pb–Pb collisions at . In memory of A. Smirnitskiy     

Photoneutron Reactions on $${}^{\mathbf{129}}$$ Xe Nuclei and Their Electromagnetic Dissociation in Colliders

The electromagnetic dissociation of ultrarelativistic nuclei has a substantial impact on the lifetime of beams in the Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC), and secondary nuclei produced upon this dissociation may have an adverse effect on collider components. At the same time, the detection of neutrons originating from the electromagnetic dissociation process makes it possible to monitor the luminosity of colliders. In order to calculate the total and partial cross sections for the electromagnetic dissociation process by the Weizsäcker–Williams method, one needs reliable photonuclear reaction models preliminarily tested via a comparison of the results that they produce with available experimental data. Since the commissioning of the LHC, attention has been given primarily to $${}^{208}$$Pb–$${}^{208}$$Pb collisions. A run involving $${}^{129}$$Xe nuclei was also performed. In contrast to the case of $${}^{208}$$Pb nuclei, for which the photonuclear reaction and electromagnetic dissociation cross sections have been measured at various laboratories, there are no data for $${}^{129}$$Xe. By employing the experimental–theoretical method, the ($$\gamma,1n$$), ($$\gamma,2n$$), ($$\gamma,3n$$), and ($$\gamma$$, abs) cross sections for the $${}^{129}$$Xe nucleus are evaluated on the basis of available data for the neighboring nucleus of $${}^{127}$$I and the combined photonuclear reaction model (CPNRM). It is found that the results of CPNRM calculations performed for $${}^{129}$$Xe at photon energies up to 40 MeV by employing the TENDL-2017 library compiled by means of the TALYS code are close to one another and are in fairly good agreement with data obtained at the Saclay laboratory for $${}^{127}$$I. These new evaluated data, the TENDL-2017 library, and approximations of the total photoabsorption cross sections above the pion production threshold are used to calculate the electromagnetic dissociation cross section for $${}^{129}$$Xe at the LHC and at the FCC-hh collider being designed. The results of these calculations are compared with their counterparts obtained on the basis of the RELDIS model.     

The productions of the top-pions and top-Higgs associated with the charm quark at the hadron colliders

In the topcolor-assisted technicolor (TC2) model, the typical physical particles, top-pions and top-Higgs, are predicted and the existence of these particles could be regarded as robust evidence for the model. These particles are accessible at the Tevatron and LHC, and furthermore the flavor-changing (FC) feature of the TC2 model may provide us with a unique opportunity to probe them. In this paper, we study some interesting FC production processes of top-pions and top-Higgs particles at the Tevatron and LHC, i.e., cΠ_t ^- and cΠ_t ⁰(h_t ⁰) productions. We find that the light charged top-pions are not favorable by the Tevatron experiments, and the Tevatron has little capability to probe the neutral top-pion and top-Higgs particles via these FC production processes. At LHC, however, the cross section can reach the level of 10–100 pb for cΠ_t ^- production and 10–100 fb for cΠ_t ⁰(h_t ⁰) production. So one can expect that enough signals could be produced at the LHC experiments. Furthermore, the SM backgrounds should be clean due to the FC feature of the processes, and the FC decay modes Π_t ^-→bc̄, Π_t ⁰(h_t ⁰)→tc̄ can provide us with the signal typical for the detection of the top-pions and top-Higgs particles. Therefore, one may have hope to find the signal of top-pions and top-Higgs particles with the running of LHC via these FC processes. PACS 12.60.Nz; 14.80.Mz; 12.15.LK; 14.65.Ha     

Cultural heritage and archaeology materials studied by synchrotron spectroscopy and imaging

The use of synchrotron radiation techniques to study cultural heritage and archaeological materials has undergone a steep increase over the past 10–15 years. The range of materials studied is very broad and encompasses painting materials, stone, glass, ceramics, metals, cellulosic and wooden materials, and a cluster of organic-based materials, in phase with the diversity observed at archaeological sites, museums, historical buildings, etc. Main areas of investigation are: (1) the study of the alteration and corrosion processes, for which the unique non-destructive speciation capabilities of X-ray absorption have proved very beneficial, (2) the understanding of the technologies and identification of the raw materials used to produce archaeological artefacts and art objects and, to a lesser extent, (3) the investigation of current or novel stabilisation, conservation and restoration practices. In terms of the synchrotron methods used, the main focus so far has been on X-ray techniques, primarily X-ray fluorescence, absorption and diffraction, and Fourier-transform infrared spectroscopy. We review here the use of these techniques from recent works published in the field demonstrating the breadth of applications and future potential offered by third generation synchrotron techniques. New developments in imaging and advanced spectroscopy, included in the UV/visible and IR ranges, could even broaden the variety of materials studied, in particular by fostering more studies on organic and complex organic–inorganic mixtures, while new support activities at synchrotron facilities might facilitate transfer of knowledge between synchrotron specialists and users from archaeology and cultural heritage sciences.     

BSM Higgs physics in the exclusive forward proton mode at the LHC

We investigate the prospects for Central Exclusive Diffractive (CED) production of BSM Higgs bosons at the LHC using forward proton detectors installed at 220 m and 420 m distance around ATLAS and/or CMS. We update a previous analysis for the MSSM taking into account improvements in the theoretical calculations and the most recent exclusion bounds from the Tevatron. We extend the MSSM analysis to new benchmark scenarios that are in agreement with the cold dark matter relic abundance and other precision measurements. We analyze the exclusive production of Higgs bosons in a model with a fourth generation of fermions. Finally, we comment on the determination of Higgs spin–parity and coupling structures at the LHC and show that the forward proton mode could provide crucial information on the CP\mathcal{CP} properties of the Higgs bosons.