CERN Super Proton Synchrotron Research Articles

Measurements of π±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi ^\\pm $$\\end{document}, K±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$K^\\pm $$\\end{document}, p and p¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\bar{p}$$\\end{document} spectra in 40Ar+45Sc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{40}\\hbox {Ar+}^{45}\\hbox {Sc}$$\\end{document} collisions at 13A to 150A GeV/c\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext{ Ge }\\hspace{-1.00006pt}\ ext{ V }\\!/\\!c$$\\end{document}

The NA61/SHINE experiment at the CERN Super Proton Synchrotron studies the onset of deconfinement in strongly interacting matter through a beam energy scan of particle production in collisions of nuclei of varied sizes. This paper presents results on inclusive double-differential spectra, transverse momentum and rapidity distributions and mean multiplicities of π±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi ^\\pm $$\\end{document}, K±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$K^\\pm $$\\end{document}, p and p¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\bar{p}$$\\end{document} produced in 40Ar+45Sc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{40}\\hbox {Ar+}^{45}\\hbox {Sc}$$\\end{document} collisions at beam momenta of 13A, 19A, 30A, 40A, 75A and 150A GeV/c\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext{ Ge }\\hspace{-1.00006pt}\ ext{ V }\\!/\\!c$$\\end{document}. The analysis uses the 10% most central collisions, where the observed forward energy defines centrality. The energy dependence of the K±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$K^\\pm $$\\end{document}/π±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi ^\\pm $$\\end{document} ratios as well as of inverse slope parameters of the K±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$K^\\pm $$\\end{document} transverse mass distributions are placed in between those found in inelastic p+p\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$p+p$$\\end{document} and central Pb + Pb collisions. The results obtained here establish a system-size dependence of hadron production properties that so far cannot be explained either within statistical or dynamical models.

Observation of fixed lines induced by a nonlinear resonance in the CERN Super Proton Synchrotron

AbstractThe motion of systems with linear restoring forces and recurring nonlinear perturbations is of central importance in physics. When a system’s natural oscillation frequencies and the frequency of the nonlinear restoring forces satisfy certain algebraic relations, the dynamics become resonant. In accelerator physics, an understanding of resonances and nonlinear dynamics is crucial for avoiding the loss of beam particles. Here we confirm the theoretical prediction of the dynamics for a single two-dimensional coupled resonance by observing so-called fixed lines. Specifically, we use the CERN Super Proton Synchrotron to measure the position of a particle beam at discrete locations around the accelerator. These measurements allow us to construct the Poincaré surface of section, which captures the main features of the dynamics in a periodic system. In our setting, any resonant particle passing through the Poincaré surface of section lies on a curve embedded in a four-dimensional phase space, the fixed line. These findings are relevant for mitigating beam degradation and thus for achieving high-intensity and high-brightness beams, as required for both current and future accelerator projects.

Digital processing and BLMASIC control prototype for the Beam Loss Monitor system in the SPS at CERN

The Beam Loss Monitoring system plays a crucial role in the CERN's Super Proton Synchrotron beam monitoring and machine protection. With the upcoming renovation of the system, the acquisition electronics can be based on an innovative ASIC designed by CERN. This paper presents the development of the control and digital processing electronics for this BLMASIC, reviews the architecture and design choices, discusses implementation details, including the controls and redundancy schemes, and highlights some preliminary results. The conclusion outlines the future development steps, and emphasises the interest of this simple and robust architecture using LpGBT and VTRx for critical systems.

Kaon beam simulations employing conventional hadron beam concepts and the RF separation technique at the CERN M2 beamline for the future AMBER experiment

The AMBER-experiment [2, 1], located in the North Experimental Area at CERN, is the successor of the NA58/COMPASS [11] experiment which ran from 2002-2022. AMBER will start its data taking in 2023. The experiment is served by the M2 beamline, employing secondary and tertiary beams produced by 400 GeV c -1 protons from the CERN Super Proton Synchrotron (SPS) impacting the T6 target. For the second phase of their measurements, AMBER will require high-intensity kaon beams [6, 7]. This requirement for high-intensity beams implies a need for accurate particle identification allowing tagging particles of interest that would otherwise be lost for analysis. The beam particle identification is carried out using Cherenkov (CEDAR) detectors [5], whose tagging efficiency depends critically on the beam divergence. In this paper we investigate the beam parameters required, the performance achievable with the current layout of the beamline, as well as possible improvements.

CERN Super Proton Synchrotron Radiation Environment and Related Radiation Hardness Assurance Implications

The Super Proton Synchrotron (SPS) is the second largest accelerator at CERN where protons are accelerated between 16 GeV/c and 450 GeV/c. Beam losses, leading to the mixed-field radiation of up to MGy magnitude, pose a threat to the reliability of the electronic equipment and polymer materials located in the tunnel and its vicinity. Particularly in the arc sectors, where both main magnets and radiation sensors are periodically arranged, the Total Ionizing Dose (TID) is of concern for the front-end electronics of A Logarithmic Position System (ALPS). The SPS is equipped with multiple radiation detection systems such as Beam Loss Monitors (BLM), RadMons, and as of 2021, the Distributed Optical Fibre Radiation Sensing (DOFRS), that combined all together provide a very comprehensive picture of both the TID spatial distribution and its time evolution. Within this study, the overview of measured 2021 and 2022 TID levels is presented, together with the demonstration of capabilities offered by the different radiation monitors. The DOFRS, supported by the passive Radio-Photo Luminescence (RPL) dosimeter measurements, is used to assess the TID values directly at the electronic racks, which turned out to be reaching several tens of Gy per year, potentially affecting the ALPS lifetime.

Flow fluctuations and kinetic freeze-out of identified hadrons at energies available at the CERN Super Proton Synchrotron

Flow fluctuations and kinetic freeze-out of identified hadrons at energies available at the CERN Super Proton Synchrotron

Long term stability studies in the presence of crab cavities and high order multipoles in the CERN super proton synchrotron and high luminosity large hadron collider

In 2018 the world’s first Crab Cavity (CC) experiments with protons were successfully performed, aiming to study the CC effect on a proton beam and evaluate the engineering challenges. Before the commencement of these experiments, the impact of the CCs and their multipoles on the long term particle stability of the SPS was studied using dynamic aperture simulations. Furthermore, in order to ensure the long term stability and luminosity performance of the LHC upgrade, the High Luminosity LHC (HL-LHC), the limits of stable motion were also examined in the presence of CC multipole errors, CC voltage errors and additional non-linearities such as the beam–beam effects. This paper presents the comprehensive dynamic aperture results for the SPS and HL-LHC for different CC, accelerator and beam configurations in view of guiding the engineering specifications of the tolerances of the crab cavity multipole errors.

Description and stability of a RPC-based calorimeter in electromagnetic and hadronic shower environments

The CALICE Semi-Digital Hadron Calorimeter technological prototype completed in 2011 is a sampling calorimeter using Glass Resistive Plate Chamber (GRPC) detectors as the active medium. This technology is one of the two options proposed for the hadron calorimeter of the International Large Detector for the International Linear Collider. The prototype was exposed in 2015 to beams of muons, electrons, and pions of different energies at the CERN Super Proton Synchrotron. The use of this technology for future experiments requires a reliable simulation of its response that can predict its performance. GEANT4 combined with a digitization algorithm was used to simulate the prototype. It describes the full path of the signal: showering, gas avalanches, charge induction, and hit triggering. The simulation was tuned using muon tracks and electromagnetic showers for accounting for detector inhomogeneity and tested on hadronic showers collected in the test beam. This publication describes developments of the digitization algorithm. It is used to predict the stability of the detector performance against various changes in the data-taking conditions, including temperature, pressure, magnetic field, GRPC width variations, and gas mixture variations. These predictions are confronted with test beam data and provide an attempt to explain the detector properties. The data-taking conditions such as temperature and potential detector inhomogeneities affect energy density measurements but have small impact on detector efficiency.

Development of a water-based cooling system for the Muon Chamber detector system of the CBM experiment

A water-based cooling system is being investigated to meet the cooling requirement of the Gas Electron Multiplier (GEM) based Muon Chamber (MuCh) detector system of the Compressed Baryonic Matter (CBM) experiment at GSI, Germany. The system is based on circulating cold water through the channels inside an aluminium plate. The aluminium plate is attached to a GEM chamber. A feasibility study is conducted on one small and two real-size prototype cooling plates. A microcontroller-based unit has been built and integrated into the system to achieve automatic control and monitoring of temperature on the plate surface. The real-size prototypes have been used in a test beam experiment at the CERN SPS (Super Proton Synchrotron) with the lead beam on a lead target. A setup using three prototype modules has been prepared in the lab for testing in a simulated real-life environment. This paper discusses the working principle, mechanical design, fabrication, and test results of the cooling prototypes in detail.

Longitudinal mode-coupling instabilities of proton bunches in the CERN Super Proton Synchrotron

In this paper, we study single-bunch instabilities observed in the CERN Super Proton Synchrotron (SPS). According to the linearized Vlasov theory, radial or azimuthal mode-coupling instabilities result from a coupling of bunch-oscillation modes, which belong to either the same or adjacent azimuthal modes, respectively. We show that both instability mechanisms exist in the SPS by applying the Oide-Yokoya approach to compute van Kampen modes for the realistic longitudinal impedance model of the SPS. The results agree with macroparticle simulations and are consistent with beam measurements. In particular, we see that the uncontrolled longitudinal emittance blowup of single bunches observed before the recent impedance reduction campaign (2018--2021) is due to the radial mode-coupling instability. Unexpectedly, this instability is as strong as the azimuthal mode-coupling instability, which is possible in the SPS for other combinations of bunch length and intensity. We also demonstrate the significant role of rf nonlinearity and potential-well distortion in determining these instability thresholds. Finally, we discuss the effect of the recent impedance reduction campaign on beam stability in single- and double-rf configurations.

Highlights from the NA61/SHINE

NA61/SHINE is a multipurpose fixed-target facility at the CERN Super Proton Synchrotron. The main goals of the NA61/SHINE stronginteractions program are to discover the critical point of strongly interacting matter as well as to determine the properties of produced particles relevant for the study of the onset of deconfinement - the transition between the state of hadronic matter and the quark-gluon plasma. An analysis of hadron production properties is performed in nucleus-nucleus, proton-proton, and proton-nucleus interactions as a function of collision energy and size of the colliding nuclei to achieve these goals. The selected NA61/SHINE results from this program are presented. In particular, the latest results from different reactions p+p, Be+Be, Ar+Sc, and Pb+Pb on hadron spectra and fluctuations are discussed. The NA61/SHINE results are compared with worldwide experiments and predictions from various theoretical models, like EPOS, PHSD, UrQMD, and others.

Results on system size dependence of strangeness production in the CERN SPS energy range from NA61/SHINE

NA61/SHINE is a multipurpose fixed-target facility at the CERN Super Proton Synchrotron. The main goals of the NA61/SHINE strong interactions program are to discover the critical point of strongly interacting matter and study the properties of the onset of deconfinement. To reach these goals, hadron production measurements are performed in the form of a two-dimensional scan by varying collision energy and system size. The Collaboration has recently finished data acquisition for its original program on strong interactions, accumulating broad data samples on hadron production in various systems in the SPS energy range. In this contribution, the NA61/SHINE results on identified charged kaon and pion production in p+p, Be+Be and Ar+Sc collisions at the SPS energy range (√SNN = 5.1 - 17.3 GeV) are presented. The NA61/SHINE measurements of small and intermediate-mass ion collisions establish an interesting system size dependence, showing a rapid change of hadron production properties that starts when moving from Be+Be to Ar+Sc system. In particular, Ar+Sc is the smallest system for which a significant enhancement of K+/π+ ratio with respect to p+p collisions is observed. Obtained energy and system size dependence of the measured charged hadron multiplicities are compared with available world data and various theoretical models.

Design of the optical system for the gamma factory proof of principle experiment at the CERN Super Proton Synchrotron

The Gamma Factory proof of principle experiment aims at colliding laser pulses with ultrarelativistic partially stripped ion beams at the CERN Super Proton Synchrotron. Its goals include the first demonstration of fast cooling of ultrarelativistic ion beams and opening up many possibilities for new physics measurements in various domains from atomic physics to particle physics. A high average-power, pulsed laser system delivering approximately 200 kW needs to be implemented for this aim. This is possible thanks to state-of-the-art optical systems that recently demonstrated similar performances in the laboratory environment. Challenges lie in the implementation of this kind of laser system in the harsh environment of hadronic machines including their robust and fully remote operation. The design of this laser system, involving a high quality factor enhancement cavity, is drawn and described in this article. Mitigation procedures are proposed to overcome limitations imposed by the occurrence of degenerate high-order mode at high average power in such optical resonators. We show that the operation at average power above 200 kW is feasible.

Hadron research with AMBER at CERN

The recently approved NA66/AMBER experiment (Apparatus for Meson and Baryon Experimental Research) at the CERN Super Proton Synchrotron pursues a broad research program in quantum chromodynamics. It ranges in its first phase from a precision measurement of the proton radius with a 100 GeV muon beam to investigating the quark-gluon structure of mesons in Drell-Yan processes. In a second phase, radio-frequency separated kaon beams will allow to extend such investigations to the strangeness sector.

The Use of the BIM Approach from the Conceptual Planning to the Construction Phase: The Case Study of the SHiP Experiment

The Search for Hidden Particles (SHiP) experiment is a new purpose fixed target facility proposed for the CERN Super Proton Synchrotron accelerator to search for long-lived exotic particles associated with Hidden Sectors and Dark Matter. This paper reports on the development of BIM integrated design for the SHiP experiment, applied initially to the Decay Volume, a >2000 m3 conical steel vessel under a vacuum hosting several large particle physics detector systems. A BIM methodology is used to address all the design phases of the Decay Volume of the SHiP experiment from the conceptual planning to the constructive drawings production. This proposed workflow is a basic plan to be repeated for each sub-component of the SHiP experiment in order to have a full and overall integration of the experiment. In particular, the Decay Volume’s geometrical and structural design and the simulation of its assembly process, both in factory and on site, are proposed. Moreover, the use of collaborative platforms to speed up the ideas exchange, as the basis of a highly multidisciplinary and complex project, is discussed. The complexity, multidisciplinary nature, and size of the SHiP project severely challenge design information management. The final plan to solve this issue is to have a BIM integrated design of each experiment sub-component, such as that demonstrated in this work for the Decay Volume, in order to have a full and multidisciplinary integration of the overall project.

Feasibility of crystal-assisted collimation in the CERN accelerator complex

Bent silicon crystals mounted on high-accuracy angular actuators were installed in the CERN Super Proton Synchrotron (SPS) and extensively tested to assess the feasibility of crystal-assisted collimation in circular hadron colliders. The adopted layout was exploited and regularly upgraded for about a decade by the UA9 Collaboration. The investigations provided the compelling evidence of a strong reduction of beam losses induced by nuclear inelastic interactions in the aligned crystals in comparison with amorphous orientation. A conceptually similar device, installed in the betatron cleaning insertion of CERN Large Hadron Collider (LHC), was operated through the complete acceleration and storage cycle and demonstrated a large reduction of the background leaking from the collimation region and radiated into the cold sections of the accelerator and the experimental detectors. The implemented layout and the relevant results of the beam tests performed in the SPS and in the LHC with stored proton and ion beams are extensively discussed.

Response of a CMS HGCAL silicon-pad electromagnetic calorimeter prototype to 20–300 GeV positrons

The Compact Muon Solenoid collaboration is designing a new high-granularity endcap calorimeter, HGCAL, to be installed later this decade. As part of this development work, a prototype system was built, with an electromagnetic section consisting of 14 double-sided structures, providing 28 sampling layers. Each sampling layer has an hexagonal module, where a multipad large-area silicon sensor is glued between an electronics circuit board and a metal baseplate. The sensor pads of approximately 1.1 cm2 are wire-bonded to the circuit board and are readout by custom integrated circuits. The prototype was extensively tested with beams at CERN's Super Proton Synchrotron in 2018. Based on the data collected with beams of positrons, with energies ranging from 20 to 300 GeV, measurements of the energy resolution and linearity, the position and angular resolutions, and the shower shapes are presented and compared to a detailed Geant4 simulation.

Hadron Production Measurements at NA61/SHINE for Precise Determination of Accelerator Neutrino Fluxes

The total systematic uncertainty of the neutrino flux in accelerator-based neutrino experiments is dominated by the Monte Carlo modeling of hadronic interactions. Direct hadron production measurements for T2K and Fermilab neutrino experiments, MINERvA, NOvA and DUNE, are being performed at the NA61/SHINE spectrometer at CERN's Super Proton Synchrotron. Crucial for improving neutrino flux predictions, hadron yields, inelastic and production cross sections are obtained at NA61/SHINE where interactions of various hadron beams with thin and thick (replica) targets are reproduced. Recently obtained results will be reported. An extension of NA61/SHINE's programme of hadron production measurements for neutrino experiments is planned beyond 2020.

K^{*}(892)^0 meson production in inelastic p+p interactions at 40 and 80 text{ GeV }!/!c beam momenta measured by NA61/SHINE at the CERN SPS

Measurements of K^{*}(892)^0 resonance production via its K^{+}pi ^{-} decay mode in inelastic p+p collisions at beam momenta 40 and 80 text{ GeV }!/!c (sqrt{s_{NN}}=8.8 and 12.3 text{ GeV }) are presented. The data were recorded by the NA61/SHINE hadron spectrometer at the CERN Super Proton Synchrotron. The template method was used to extract the K^{*}(892)^0 signal. Transverse momentum and rapidity spectra were obtained. The mean multiplicities of K^{*}(892)^0 mesons were found to be (35.1 pm 1.3 mathrm {(stat)} pm 3.6 mathrm {(sys))} cdot 10^{-3} at 40 text{ GeV }!/!c and (58.3 pm 1.9 mathrm {(stat)} pm 4.9 mathrm {(sys))} cdot 10^{-3} at 80 text{ GeV }!/!c. The NA61/SHINE results are compared with the Epos1.99 and Hadron Resonance Gas models as well as with world data. The transverse mass spectra of K^{*}(892)^0 mesons and other particles previously reported by NA61/SHINE were fitted within the Blast-Wave model. The transverse flow velocities are close to 0.1–0.2 of the speed of light and are significantly smaller than the ones determined in heavy nucleus-nucleus interactions at the same beam momenta.

Prospects in the search for a new light Z′ boson with the NA64μ experiment at the CERN SPS

A light ${Z}^{\ensuremath{'}}$ vector boson coupled to the second and third lepton generations through the ${L}_{\ensuremath{\mu}}\ensuremath{-}{L}_{\ensuremath{\tau}}$ current with mass below 200 MeV provides a very viable explanation in terms of new physics to the recently confirmed $(g\ensuremath{-}2{)}_{\ensuremath{\mu}}$ anomaly. This boson can be produced in the bremsstrahlung reaction $\ensuremath{\mu}N\ensuremath{\rightarrow}\ensuremath{\mu}N{Z}^{\ensuremath{'}}$ after a high energy muon beam collides with a target. $\mathrm{NA}64\ensuremath{\mu}$ is a fixed-target experiment using a 160 GeV muon beam from the CERN Super Proton Synchrotron accelerator looking for ${Z}^{\ensuremath{'}}$ production and its subsequent decays, ${Z}^{\ensuremath{'}}\ensuremath{\rightarrow}\mathrm{invisible}$. In this paper, we present the study of the $\mathrm{NA}64\ensuremath{\mu}$ sensitivity to search for such a boson. This includes a realistic beam simulation, a detailed description of the detectors and a discussion about the main potential background sources. A pilot run is scheduled in order to validate the simulation results. If those are confirmed, $\mathrm{NA}64\ensuremath{\mu}$ will be able to explore all the remaining parameter space which could provide an explanation for the $g\ensuremath{-}2$ muon anomaly in the ${L}_{\ensuremath{\mu}}\ensuremath{-}{L}_{\ensuremath{\tau}}$ model.