High Energy Hadron Research Articles

Space-Time Development of Electromagnetic and Hadronic Showers and Perspectives for Novel Calorimetric Techniques

The performance of hadronic calorimeters will be a key parameter at the next generation of High Energy Physics accelerators. A detector combining fine granularity with excellent timing information would prove beneficial for the reconstruction of both jets and electromagnetic particles with high energy resolution. In this work, the space and time structure of high energy showers is studied by means of a Geant 4-based simulation toolkit. In particular, the relevant time scales of the different physics phenomena contributing to the energy loss are investigated. A correlation between the fluctuations of the energy deposition of high energy hadrons and the time development of the showers is observed, which allows for an event-by-event correction to be computed to improve the energy resolution of the calorimeter. These studies are intended to set the basic requirements for the development of a new-concept, total absorption time-imaging calorimeter, which seems now within reach thanks to major technological advancements in the production of fast scintillating materials and compact photodetectors.

Two scales in Bose–Einstein correlations

We argue that the secondaries produced in high energy hadron collisions are emitted by small size sources distributed over a much larger area in impact parameter space occupied by the interaction amplitude. That is, Bose-Einstein correlation of two emitted identical particles should be described by a `two-radii' parametrization ansatz. We discuss the expected energy, charged multiplicity and transverse momentum of the pair (that is, $\sqrt{s},~N_{\rm ch}, k_t$) behaviour of both the small and large size components.

The edge transient-current technique (E-TCT) with high energy hadron beam

We propose a novel way to investigate the properties of silicon and CVD diamond detectors for High Energy Physics experiments complementary to the already well-established E-TCT technique using laser beam. In the proposed setup the beam of high energy hadrons (MIPs) is used instead of laser beam. MIPs incident on the detector in the direction parallel to the readout electrode plane and perpendicular to the edge of the detector. Such experiment could prove very useful to study CVD diamond detectors that are almost inaccessible for the E-TCT measurements with laser due to large band-gap as well as to verify and complement the E-TCT measurements of silicon.The method proposed is being tested at CERN in a beam of 120GeV hadrons using a reference telescope with track resolution at the DUT of few μm. The preliminary results of the measurements are presented.

Transverse Spin Azimuthal Asymmetries in SIDIS at COMPASS: Multidimensional Analysis

COMPASS is a high-energy physics experiment operating at the SPS at CERN. Wide physics program of the experiment comprises study of hadron structure and spectroscopy with high energy muon and hadrons beams. As for the muon-program, one of the important objectives of the COMPASS experiment is the exploration of the transverse spin structure of the nucleon via spin (in)dependent azimuthal asymmetries in single-hadron production in deep inelastic scattering of polarized leptons off transversely polarized target. For this purpose a series of measurements were made in COMPASS, using 160 GeV/c longitudinally polarized muon beam and transversely polarized [Formula: see text] (in 2002, 2003 and 2004) and [Formula: see text] (in 2007 and 2010) targets. The experimental results obtained by COMPASS for unpolarized target azimuthal asymmetries, Sivers and Collins effects and other azimuthal observables play an important role in the general understanding of the three-dimensional nature of the nucleon. Giving access to the entire twsit-2 set of transverse momentum dependent parton distribution functions and fragmentation functions COMPASS data triggers constant theoretical interest and is being widely used in phenomenological analyses and global data fits. In this review main focus is given to the very recent results obtained by the COMPASS collaboration from first ever multi-dimensional extraction of transverse spin asymmetries.

Magnetic monopole search with the MoEDAL test trapping detector

IMoEDAL is designed to search for monopoles produced in high-energy Large Hadron Collider (LHC) collisions, based on two complementary techniques: nucleartrack detectors for high-ionisation signatures and other highly ionising avatars of new physics, and trapping volumes for direct magnetic charge measurements with a superconducting magnetometer. The MoEDAL test trapping detector array deployed in 2012, consisting of over 600 aluminium samples, was analysed and found to be consistent with zero trapped magnetic charge. Stopping acceptances are obtained from a simulation of monopole propagation in matter for a range of charges and masses, allowing to set modelindependent and model-dependent limits on monopole production cross sections. Multiples of the fundamental Dirac magnetic charge are probed for the first time at the LHC.

Highlights from the COMPASS experiment at CERN. Hadron spectroscopy and excitations

The COMPASS experiment at the CERN-SPS studies the spectrum and the structure of hadrons by scattering high energy hadrons and polarised muons off various fixed targets. Recent results for the hadron programme comprise highlights from different topics. A selective overview is given and, among others, the following results are discussed. The precise determination of the pion polarisability, a long standing puzzle that has been solved now, is presented as well as measurements of radiative widths. The observation of a new narrow axial-vector state, the $a_1(1420)$, as well as deeper insights into the exotic $1^{-+}$-wave, which is under study since decades by several experiments, are discussed and further, the search for the charmonium-like exotic $Z_c(3900)$ state in the COMPASS data is covered.

Production of heavy quarkonia in hadronic experiments

The phenomenology of the production of P-wave χ c,b mesons and S-wave η c,b mesons in highenergy hadron–hadron collisions was studied on the basis of nonrelativistic quantum chromodynamics (NRQCD). Available experimental data on χ c -meson production were analyzed, and nonperturbative NRQCDmatrix elements were determined from a fit to these data. It is shown that the observed transversemomentum (pT) spectrum of χ c mesons is basically formed by color-singlet contributions. At the same time, the ratio σ(χ c2)/σ(χ c1) depends greatly on color-octet contributions; this ratio therefore becomes a highly sensitive tool for separating different NRQCD contributions. Predictions for χ b -meson production are obtained on the basis of NRQCD scaling rules. For the case of η c -meson production, it is shown that the observed cross sections agree with the color-singlet model featuring phenomenological parameters.

Radiation testing campaign results for understanding the suitability of FPGAs in detector electronics

SRAM based Field Programmable Gate Arrays (FPGAs) have been rarely used in High Energy Physics (HEP) due to their sensitivity to radiation. The last generation of commercial FPGAs based on 28nm feature size and on Silicon On Insulator (SOI) technologies are more tolerant to radiation to the level that their use in front-end electronics is now feasible. FPGAs provide re-programmability, high-speed computation and fast data transmission through the embedded serial transceivers. They could replace custom application specific integrated circuits in front end electronics in locations with moderate radiation field. The use of a FPGA in HEP experiments is only limited by our ability to mitigate single event effects induced by the high energy hadrons present in the radiation field.

Preliminary design of the beam screen cooling for the Future Circular Collider of hadron beams

Following recommendations of the recent update of the European strategy in particle physics, CERN has undertaken an international study of possible future circular colliders beyond the LHC. This study considers an option for a very high energy (100 TeV) hadron-hadron collider located in a quasi-circular underground tunnel having a circumference of 80 to 100 km. The synchrotron radiation emitted by the high-energy hadron beam increases by more than two orders of magnitude compared to the LHC. To reduce the entropic load on the superconducting magnets’ refrigeration system, beam screens are indispensable to extract the heat load at a higher temperature level. After illustrating the decisive constraints of the beam screen's refrigeration design, this paper presents a preliminary design of the length of a continuous cooling loop comparing helium and neon, for different cooling channel geometries with emphasis on the cooling length limitations and the exergetic efficiency.

Progress with High-Field Superconducting Magnets for High-Energy Colliders

One of the possible next steps for high-energy physics research relies on a high-energy hadron or muon collider. The energy of a circular collider is limited by the strength of bending dipoles, and its maximum luminosity is determined by the strength of final focus quadrupoles. For this reason, the high-energy physics and accelerator communities have shown much interest in higher-field and higher-gradient superconducting accelerator magnets. The maximum field of NbTi magnets used in all present high-energy machines, including the LHC, is limited to ∼10 T at 1.9 K. Fields above 10 T became possible with the use of Nb3Sn superconductors. Nb3Sn accelerator magnets can provide operating fields up to ∼15 T and can significantly increase the coil temperature margin. Accelerator magnets with operating fields above 15 T require high-temperature superconductors. This review discusses the status and main results of Nb3Sn accelerator magnet research and development and work toward 20-T magnets.

Photon-tagged and B-meson-tagged b-jet production at the LHC

Tagged jet measurements in high energy hadronic and nuclear reactions provide constraints on the energy and parton flavor origin of the parton shower that recoils against the tagging particle. Such additional insight can be especially beneficial in illuminating the mechanisms of heavy flavor production in proton–proton collisions at the LHC and their modification in the heavy ion environment, which are not fully understood. With this motivation, we present theoretical results for isolated-photon-tagged and B-meson-tagged b-jet production at sNN=5.1 TeV for comparison to the upcoming lead–lead data. We find that photon-tagged b-jets exhibit smaller momentum imbalance shift in nuclear matter, and correspondingly smaller energy loss, than photon-tagged light flavor jets. Our results show that B-meson tagging is most effective in ensuring that the dominant fraction of recoiling jets originate from prompt b-quarks. Interestingly, in this channel the large suppression of the cross section is not accompanied by a significant momentum imbalance shift.

Self-similarity of hadron production: z-scaling

We briefly review z-scaling as a reflection of the self-similarity of hadron production in high-energy hadron and nuclear collisions and discuss the basic principles of constituent interactions (locality, self-similarity, and fractality). We present results of analyzing experimental data on the inclusive pT spectra of hadron and jet production at the RHIC, Tevatron, and LHC in the framework of z-scaling.

Scaling and asymptotic properties of evaporated neutron inclusive cross sections in high energy hadron–nucleus and nucleus–nucleus interactions

New properties of the evaporated neutron (E < 30 MeV) energy spectra in hadron–nucleus interactions have been found. Particularly, the spectra approach the asymptotic regime, namely, they weakly depend on the collision energy at momenta of projectile protons larger than 5–6 GeV/c; the spectra for various nuclei are similar, and can be approximately described by the function Anf(E). Experimental data on neutron spectra in the case of projectile π-mesons show analogous behavior, but the statistics of the data do not allow one to draw clear conclusions. In our analysis we used ITEP experimental data on inclusive cross sections of neutrons produced in interactions of π-mesons and protons with various nuclei in the energy range from 747 MeV up to 8.1 GeV. The observed properties allow one to predict neutron yields in the nucleus–nucleus interactions at high and super high energies. Predictions for the NICA/MPD experiment at JINR are presented. It is shown that the FTF (Fritiof)-model of the Geant4 toolkit qualitatively reproduces the observed regularities. For the first time estimates of the neutron energy flows are obtained at both RHIC and LHC energies.

Accelerator physics and technology challenges of very high energy hadron colliders

High energy hadron colliders have been in the forefront of particle physics for more than three decades. At present, international particle physics community considers several options for a 100 TeV proton–proton collider as a possible post-LHC energy frontier facility. The method of colliding beams has not fully exhausted its potential but has slowed down considerably in its progress. This paper briefly reviews the accelerator physics and technology challenges of the future very high energy colliders and outlines the areas of required research and development towards their technical and financial feasibility.

Evaluation of commercial ADC radiation tolerance for accelerator experiments

Electronic components used in high energy physics experiments are subjected to a radiation background composed of high energy hadrons, mesons and photons. These particles can induce permanent and transient effects that affect the normal device operation. Ionizing dose and displacement damage can cause chronic damage which disable the device permanently. Transient effects or single event effects are in general recoverable with time intervals that depend on the nature of the failure. The magnitude of these effects is technology dependent with feature size being one of the key parameters. Analog to digital converters are components that are frequently used in detector front end electronics, generally placed as close as possible to the sensing elements to maximize signal fidelity. We report on the development of a technique for testing analog to digital converters for radiation effects, in particular for single event effects. A total of seventeen commercial ADCs were evaluated for ionizing dose tolerance and extensive SEU measurements performed on a twelve and fourteen bit ADCs. Mitigation strategies for single event effects (SEE) are discussed for their use in the large hadron collider environment.

Probing gauge-phobic heavy Higgs bosons at high energy hadron colliders

We study the probe of the gauge-phobic (or nearly gauge-phobic) heavy Higgs bosons (GPHB) at high energy hadron colliders including the 14 TeV LHC and the 50 TeV Super Proton–Proton Collider (SppC). We take the process pp→tt¯tt¯, and study it at the hadron level including simulating the jet formation and top quark tagging (with jet substructure). We show that, for a GPHB with MH<800 GeV, MH can be determined by adjusting the value of MH in the theoretical pT(b1) distribution to fit the observed pT(b1) distribution, and the resonance peak can be seen at the SppC for MH=800 GeV and 1 TeV.

Support for massless particles in Chaos Many-Body Engine simulations of nuclear collisions at relativistic energies

Following the goal of improving the relativistic nuclear collisions toy-model proposed in Grossu et al. (2014), we added support for massless particles in all “Many-Body”, “High Precision”, and “Reactions” modules of the Chaos Many-Body Engine application. In this context, we discuss a first CMBE–HIJING comparative study on nuclear collisions at the maximum BNL energy. As a new high precision example of use, we implemented a 50 decimals precision simulation of a bound system composed by two massless particles with gravitational potential. New version program summaryProgram title: Chaos Many-Body Engine v06Catalogue identifier: AEGH_v6_0Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEGH_v6_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: Microsoft Public License (Ms-PL)No. of lines in distributed program, including test data, etc.: 1087674No. of bytes in distributed program, including test data, etc.: 46861801Distribution format: tar.gzProgramming language: C# 4.0Computer: PCOperating system: Net Framework 4.0 running on MS WindowsRAM: 128 MBClassification: 24.60.Lz, 05.45.aCatalogue identifier of previous version: AEGH_v5_0Journal reference of previous version: Computer Physics Communications 185 (2014) 3059Does the new version supersede the previous version?: YesNature of problem: Treatment of massless particles in simulations of relativistic many-body systems.Solution method: Relativistic many-body OOP engine, including a reactions module.Reasons for new version:1.Adding support for massless particles in CMBE simulations of relativistic many-body systems with reactions.Summary of revisions:1.Treatment of massless particles in all CMBE modules: Many-Body Engine, High Precision Framework, and Reactions Engine.2.Simulations∖Collider: Addition of some reactions with photons to the existing toy-model for chaos analysis of relativistic nuclear collisions at present BNL energies.3.HighPrecision∖MasslessParticles: Implementation of a new high precision example of use (a bound system composed by 2-massless particles with gravitational potential).4.Help∖Options: CMBE options (e.g. the high precision maximum number of decimals).5.GUI improvements (e.g. implementation of a new user control for high precision numbers I/O).Additional comments:The Many-Body Engine Module. For regular particles, CMBE provides a calculated property (Particle.RelativisticMass) for obtaining the relativistic mass as a function of velocity. As this approach cannot be used for massless particles, the dependency on momentum (m=p/c) was considered instead. The main impact of this change is related to the implementation of the second Newton’s law. Thus, the Next methods, of both Nbody and BigNBody classes, were modified accordingly.The Reactions Engine Module. The previous mentioned relation between momentum and relativistic mass was also used for the massless particles involved in both bi-particle reactions and decays (the ReactionEngine.GetreactionOutput and ReactionEngine.GetDecayOutput methods). For the particular case when the decay massless products are emitted along the movement direction we applied the Doppler shift equation [2]: (1)υo=υe1±β1−β2 where υo is the observed frequency, and υe the emitted frequency.The Toy-Model for Relativistic Nuclear Collision at present BNL energies. Following the goal of improving the relativistic nuclear collisions toy-model proposed in [1], we added the following reactions with photons (see the ColliderReactions.xml configuration file):π0→γ+γγ+p→p̃+p+pγ+p̃→p̃+p+p̃p+p̃→γ+γγ+n→ñ+n+nγ+ñ→ñ+n+ñn+ñ→γ+γ. HIJING [3,4] is a Monte Carlo program based on QCD models for multiple jets production. In Fig. 1 we present, for exemplification, a CMBE–HIJING comparative analysis for 100 Cu + Cu ultracentral collisions at 200 A GeV/c, the maximum BNL energy [5].The differences between CMBE and HIJING can be explained by both, dissimilarities in the reaction lists, and by the fact that HIJING takes into account the minijet production, with increasing weight for high-energy hadron and nuclear interactions. In relativistic heavy-ion collisions, minijets are responsible for the main transverse energy production in the central rapidity region. This generates, at least in part, the differences between HIJING and CMBE, mainly observed at mid-rapidity. Furthermore, HIJING also incorporates nuclear effects such as final state interactions and parton shadowing for heavy-ion interactions. [Display omitted] [Display omitted] High precision framework — new example of use. As an exemplification of CMBE high precision capabilities, we considered also a bound system composed of 2 identical massless particles with gravitational potential. By imposing also the stationary de Broglie wave condition, we obtained the following simple equations:(2)m=nmP(3)r=nℏcmP where m is the relativistic mass, r the system radius, n the principal quantum number, and mP the Planck mass. Taking into account the magnitude order of quantities involved, we chose to work at 50 decimals precision (see the Help/Options, “Max. number of decimals” CMBE setting).AcknowledgmentThis study is supported by a grant of the Romanian National Authority for Scientific Research, CNCS–UEFISCDI, project number 34/05.10.2011 PN-II-ID-PCE.

Heavy color-octet particles at the LHC

Many new-physics models, especially those with a color-triplet top-quark partner, contain a heavy color-octet state. The “naturalness” argument for a light Higgs boson requires that the color-octet state be not much heavier than a TeV, and thus it can be pair-produced with large cross sections at high-energy hadron colliders. It may decay preferentially to a top quark plus a top partner, which subsequently decays to a top quark plus a color-singlet state. This singlet can serve as a WIMP dark-matter candidate. Such decay chains lead to a spectacular signal of four top quarks plus missing energy. We pursue a general categorization of the color-octet states and their decay products according to their spin and gauge quantum numbers. We review the current bounds on the new states at the LHC and study the expected discovery reach at the 8-TeV and 14-TeV runs. We also present the production rates at a future 100-TeV hadron collider, where the cross sections will be many orders of magnitude greater than at the 14-TeV LHC. Furthermore, we explore the extent to which one can determine the color octet’s mass, spin, and chiral couplings. Finally, we propose a test to determine whether the fermionic color octet is a Majorana particle.

Top-quark initiated processes at high-energy hadron colliders

In hadronic collisions at high energies, the top-quark may be treated as a parton inside a hadron. Top-quark initiated processes become increasingly important since the top-quark luminosity can reach a few percent of the bottom-quark luminosity. In the production of a heavy particle $H$ with mass $m_H > m_t$, treating the top-quark as a parton allows us to resum large logarithms $\log(m_{H}^{2}/m_{t}^{2}$) arising from collinear splitting in the initial state. We quantify the effect of collinear resummation at the 14-TeV LHC and a future 100-TeV hadron collider, focusing on the top-quark open-flavor process $gg\to t\bar t H$ in comparison with $t\bar t \to H$ and $tg\rightarrow tH$ at the leading order (LO) in QCD. We employ top-quark parton distribution functions with appropriate collinear subtraction and power counting. We find that (1) Collinear resummation enhances the inclusive production of a heavy particle with $m_H\approx$ 5 TeV (0.5 TeV) by more than a factor of two compared to the open-flavor process at a 100-TeV (14-TeV) collider; (2) Top-quark mass effects are important for scales $m_H$ near the top-quark threshold, where the cross section is largest. We advocate a modification of the ACOT factorization scheme, dubbed m-ACOT, to consistently treat heavy-quark masses in hadronic collisions; (3) The scale uncertainty of the total cross section in m-ACOT is of about 20 percent at the LO. While a higher-order calculation is indispensable for a precise prediction, the LO cross section is well described by the process $t\bar t\to H$ using an effective factorization scale significantly lower than $m_H$. We illustrate our results by the example of a heavy spin-0 particle. Our main results also apply to the production of particles with spin-1 and 2.

Calorimeters for Precision Timing Measurements in High Energy Physics

Current and future high energy physics particle colliders are capable to provide instantaneous luminosities of 1034 cm-2s-1 and above. The high center of mass energy, the large number of simultaneous collision of beam particles in the experiments and the very high repetition rates of the collision events pose huge challenges. They result in extremely high particle fluxes, causing very high occupancies in the particle physics detectors operating at these machines. To reconstruct the physics events, the detectors have to make as much information as possible available on the final state particles. We discuss how timing information with a precision of around 10 ps and below can aid the reconstruction of the physics events under such challenging conditions. High energy photons play a crucial role in this context. About one third of the particle flux originating from high energy hadron collisions is detected as photons, stemming from the decays of neutral mesons. In addition, many key physics signatures under study are identified by high energy photons in the final state. They pose a particular challenge in that they can only be detected once they convert in the detector material. The particular challenge in measuring the time of arrival of a high energy photon lies in the stochastic component of the distance to the initial conversion and the size of the electromagnetic shower. They extend spatially over distances which propagation times of the initial photon and the subsequent electromagnetic shower which are large compared to the desired precision. We present studies and measurements from test beams and a cosmic muon test stand for calorimeter based timing measurements to explore the ultimate timing precision achievable for high energy photons of 10 GeV and above. We put particular focus on techniques to measure the timing with a precision of about 10 ps in association with the energy of the photon. For calorimeters utilizing scintillating materials and light guiding components, the propagation speed of the scintillation light in the calorimeter is important. We present studies and measurements of the propagation speed on a range of detector geometries. Finally, possible applications of precision timing in future high energy physics experiments are discussed.