Current Particle Physics Research Articles

Early-career researchers in instrumentation

Early-career researchers (ECRs) play a crucial role in current particle physics experiments such as at the Large Hadron Collider. Because future experiments in particle physics can take decades to be conceptualised, designed and built, today’s ECRs are the leaders of the experiments of tomorrow. In 2021, the ECFA ECR Panel conducted a survey to collect community input on training in instrumentation for the ECFA Detector R&D Roadmap Symposium on Training. Additionally, this poll also pointed to issues that ECRs in instrumentation are facing such as a lack of networking opportunities, missing recognition and issues of diversity. The goal of this proceeding is to stimulate discussion about the needs of ECRs in instrumentation and list possible actions that can be taken to help them.

Radiation hardness of Hamamatsu H12700/H8500 MAPMTs, entrance glass windows, and p-terphenyl wavelength shifting coating under neutron and [formula omitted]Co gamma irradiation

Photomultiplier tubes, in particular multianode photomultiplier tubes, are often used in current accelerator-based nuclear and particle physics experiments for spatially resolved detection of single photons. With increasing luminosity and harsh radiation background, the radiation hardness of these sensors plays an increasingly important role. In an extensive experimental study we have investigated the effects of neutron irradiation, using a fission neutron source, and energetic 60Co γ-irradiation on commercially available Hamamatsu H12700/H8500 MAPMTs. In addition, individual components were irradiated, such as their glass windows and voltage dividers. Additionally, a p-terphenyl based wavelength shifting coating, which can be applied on the MAPMT window to enhance the photon yield, was also tested for its radiation tolerance.

Laboratory limits on the annihilation or decay of dark matter particles

Abstract Constraints on the indirect detection of dark matter are usually obtained from observations of astrophysical objects—the Galactic Center, dwarf galaxies, M31, etc. Here we propose instead to look for the annihilation or decay of dark matter particles taking place inside detectors searching directly for dark matter or in large neutrino experiments. We show that the data from XENON1T and Borexino set limits on the annihilation and decay rates of dark matter particles with masses in the keV to few MeV range. All relevant final states are considered: annihilation into γγ and e−e+ and decays into γγ, γν, and e−e+. The expected sensitivities in XENONnT, DARWIN, JUNO, and THEIA are also computed. Though weaker than current astrophysical bounds, the laboratory limits (and projections) obtained are free from the usual astrophysical uncertainties associated with J-factors and unknown backgrounds, and may thus offer a complementary probe of the dark matter properties. We point out that current and future (astro)particle physics detectors might also be used to set analogous limits for different decays and dark matter masses above a few MeV.

Bayesian neural networks for fast SUSY predictions

One of the goals of current particle physics research is to obtain evidence for new physics, that is, physics beyond the Standard Model (BSM), at accelerators such as the Large Hadron Collider (LHC) at CERN. The searches for new physics are often guided by BSM theories that depend on many unknown parameters, which, in some cases, makes testing their predictions difficult. In this paper, machine learning is used to model the mapping from the parameter space of the phenomenological Minimal Supersymmetric Standard Model (pMSSM), a BSM theory with 19 free parameters, to some of its predictions. Bayesian neural networks are used to predict cross sections for arbitrary pMSSM parameter points, the mass of the associated lightest neutral Higgs boson, and the theoretical viability of the parameter points. All three quantities are modeled with average percent errors of 3.34% or less and in a time significantly shorter than is possible with the supersymmetry codes from which the results are derived. These results are a further demonstration of the potential for machine learning to model accurately the mapping from the high dimensional spaces of BSM theories to their predictions.

Craig on the Resurrection: A Defense

This article is a rebuttal to Robert G. Cavin and Carlos A. Colombetti’s article, “Assessing the Resurrection Hypothesis: Problems with Craig’s Inference to the Best Explanation,” which argues that the Standard Model of current particle physics entails that non-physical things (like a supernatural God or a supernaturally resurrected body) can have no causal contact with the physical universe. As such, they argue that William Lane Craig’s resurrection hypothesis is not only incompatible with the notion of Jesus physically appearing to the disciples, but the resurrection hypothesis is significantly limited in both its explanatory scope and explanatory power. This article seeks to demonstrate why their use of the Standard Model does not logically entail a rejection of the physical resurrection of Jesus when considering the scope and limitations of science itself.

Consistency of the standard model effective field theory

We derive bounds on couplings in the standard model effective field theory (SMEFT) as a consequence of causality and the analytic structure of scattering amplitudes. In the SMEFT, there are 64 independent operators at mass dimension eight that are quartic in bosons (either Higgs or gauge fields) and that contain four derivatives and/or field strengths, including both CP-conserving and CP-violating operators. Using analytic dispersion relation arguments for two-to-two bosonic scattering amplitudes, we derive 27 independent bounds on the sign or magnitude of the couplings. We show that these bounds also follow as a consequence of causality of signal propagation in nonvacuum SM backgrounds. These bounds come in two qualitative forms: i) positivity of (various linear combinations of) couplings of CP-even operators and ii) upper bounds on the magnitude of CP-odd operators in terms of (products of) CP-even couplings. We exhibit various classes of example completions, which all satisfy our EFT bounds. These bounds have consequences for current and future particle physics experiments, as part of the observable parameter space is inconsistent with causality and analyticity. To demonstrate the impact of our bounds, we consider applications both to SMEFT constraints derived at colliders and to limits on the neutron electric dipole moment, highlighting the connection between such searches suggested by infrared consistency.

Anomalies in b→s Transitions and Dark Matter

Since 2013, the LHCb collaboration has reported on the measurement of several observables associated with b→s transitions, finding various deviations from their predicted values in the Standard Model. These include a set of deviations in branching ratios and angular observables, as well as in the observables RK and RK⁎, specially built to test the possible violation of Lepton Flavor Universality. Even though these tantalizing hints are not conclusive yet, the b→s anomalies have gained considerable attention in the flavor community. Here we review new physics models that address these anomalies and explore their possible connection to the dark matter of the Universe. After discussing some of the ideas introduced in these works and classifying the proposed models, two selected examples are presented in detail in order to illustrate the potential interplay between these two areas of current particle physics.

Wrong sign bottom Yukawa coupling in low energy supersymmetry

The study of the Higgs boson properties is one of the most relevant activities in current particle physics. In particular, the Higgs boson couplings to third generation fermions is an important test of the mechanism of mass generation. In spite of their impact on the production and decay properties of the Higgs boson, the values of these couplings are still uncertain and, in models of new physics, they can differ in magnitude as well as in sign with respect to the Standard Model case. In this article, we study the possibility of a wrong sign bottom-quark Yukawa coupling within the framework of the Minimal and Next-to-Minimal Supersymmetric Standard Model. Possible experimental tests are also discussed, including novel decays of the heavy CP-even and CP-odd Higgs fields that may be probed in the near future and that may lead to an explanation of some intriguing di-boson signatures observed at the ATLAS experiment.

Lepton flavor violating decays ofBandKmesons in models with extended gauge group

Lepton flavor violating (LFV) decays are forbidden in the Standard Model (SM) and to explore them one has to go beyond it. The flavor changing neutral current induced lepton flavor conserving and LFV decays of [Formula: see text] and [Formula: see text] mesons is discussed in the gauge group [Formula: see text]. The lepto-quark [Formula: see text] corresponding to gauge group [Formula: see text] allows the quark–lepton transitions and hence giving a framework to construct the effective Lagrangian for the LFV decays. The mass of lepto-quark [Formula: see text] provides a scale at which the gauge group [Formula: see text] is broken to the SM gauge group. Using the most stringent experimental limit [Formula: see text], the upper bound on the effective coupling constant [Formula: see text] is obtained for certain pairing of lepton and quark generations in the representation [Formula: see text] of the group [Formula: see text]. Later, the effective Lagrangian for the LFV meson decays for the gauge group [Formula: see text] is constructed. Using [Formula: see text], the bound on the ratio of effective couplings is obtained to be [Formula: see text]. A number of decay modes are discussed which provide a promising area to test this model in the current and future particle physics experiments.

A New Track Reconstruction Algorithm suitable for Parallel Processing based on Hit Triplets and Broken Lines

Track reconstruction in high track multiplicity environments at current and future high rate particle physics experiments is a big challenge and very time consuming. The search for track seeds and the fitting of track candidates are usually the most time consuming steps in the track reconstruction. Here, a new and fast track reconstruction method based on hit triplets is proposed which exploits a three-dimensional fit model including multiple scattering and hit uncertainties from the very start, including the search for track seeds. The hit triplet based reconstruction method assumes a homogeneous magnetic field which allows to give an analytical solutions for the triplet fit result. This method is highly parallelizable, needs fewer operations than other standard track reconstruction methods and is therefore ideal for the implementation on parallel computing architectures. The proposed track reconstruction algorithm has been studied in the context of the Mu3e-experiment and a typical LHC experiment.

磁单极子的数理分析与延拓

研究高能量宇宙质量粒子的空间结构是当前粒子物理学急需解决的课题。数学理论研究表明，一类磁单极子是存在的，属于玻色子与费米子构成的夸克混合态，其单元基态存在正反，满足两个6 × 6，4 × 4标量矩阵。在空间度规上叠加，异性磁单极子根据有限加法群和非阿尔贝群理论与色动力学原理，形成耦合渐近的强力胶子态；根据有限乘法群理论，形成另一种动量传递的量子纠缠弱力态磁场。其强力与弱力混合态构成相反电性的一类基本粒子——电子。 To study the quality of high-energy cosmic particles of the spatial structure is the current particle physics issues that need to be resolved. Mathematical theory studies have shown that a class of magnetic monopoles exist, and they are bosons and fermions mixed state composed of quarks, which means that there is positive and negative ground state satisfying two 6 × 6, 4 × 4 scalar ma-trices. In metric space overlay, according to finite additive group, non-abelian group and chromo-dynamic theory, superposition of dissimilar magnetic monopoles on space time scale forms asymptotic strong coupled gluons. However, in accordance with finite multiplicative group theory, it forms another kind of quantum entanglement weak magnetic field for transmission of momentum, where strong force and weak force mixed state constitute opposite electric fundamental par-ticle—electron.

The 3-3-1 Models in Current Particle Physics

We review the main contribution of the Division for Theoretical Particle Physics at the Institute ofPhysics, VAST in building the models based on \(\text{SU}(3)_C\otimes \text{SU}(3)_L \otimes \text{U}(1)_X\) gauge unification.

Silicon detectors for the sLHC

In current particle physics experiments, silicon strip detectors are widely used as part of the inner tracking layers. A foreseeable large-scale application for such detectors consists of the luminosity upgrade of the Large Hadron Collider (LHC), the super-LHC or sLHC, where silicon detectors with extreme radiation hardness are required. The mission statement of the CERN RD50 Collaboration is the development of radiation-hard semiconductor devices for very high luminosity colliders. As a consequence, the aim of the R&D programme presented in this article is to develop silicon particle detectors able to operate at sLHC conditions. Research has progressed in different areas, such as defect characterisation, defect engineering and full detector systems. Recent results from these areas will be presented. This includes in particular an improved understanding of the macroscopic changes of the effective doping concentration based on identification of the individual microscopic defects, results from irradiation with a mix of different particle types as expected for the sLHC, and the observation of charge multiplication effects in heavily irradiated detectors at very high bias voltages.

Atomic precision tests and light scalar couplings

We calculate the shift in the atomic energy levels induced by the presence of a scalar field which couples to matter and photons. We find that a combination of atomic measurements can be used to probe both these couplings independently. A new and stringent bound on the matter coupling springs from the precise measurement of the 1s to 2s energy level difference in the hydrogen atom, while the coupling to photons is essentially constrained by the Lamb shift. Combining these constraints with current particle physics bounds we find that the contribution of a scalar field to the recently claimed discrepancy in the proton radius measured using electronic and muonic atoms is negligible.

Note on the pseudo-Nambu-Goldstone boson of meta-stable SUSY violation

Many models of meta-stable supersymmetry (SUSY) breaking lead to a very light scalar pseudo-Nambu Goldstone boson (PNGB), P, associated with spontaneous breakdown of a baryon number like symmetry in the hidden sector. Current particle physics data provide no useful constraints on the existence of P. For example, the predicted decay rates for both K --> pi + P, b--> s + P and Upsilon --> photon + P are many orders of magnitude below the present experimental bounds. We also consider astrophysical implications of the PNGB and find a significant constraint from its effect on the evolution of red giants. This constraint either rules out models with a hidden sector gauge group larger than SU(4), or requires a new intermediate scale, of order at most 10^{10} GeV, at which the hidden sector baryon number is explicitly broken.

What are the phenomena of physics?

Depending on different positions in the debate on scientific realism, there are various accounts of the phenomena of physics. For scientific realists like Bogen and Woodward, phenomena are matters of fact in nature, i.e., the effects explained and predicted by physical theories. For empiricists like van Fraassen, the phenomena of physics are the appearances observed or perceived by sensory experience. Constructivists, however, regard the phenomena of physics as artificial structures generated by experimental and mathematical methods. My paper investigates the historical background of these different meanings of “phenomenon” in the traditions of physics and philosophy. In particular, I discuss Newton’s account of the phenomena and Bohr’s view of quantum phenomena, their relation to the philosophical discussion, and to data and evidence in current particle physics and quantum optics.

Review of Cherenkov imaging devices in particle and nuclear physics experiments

This review summarizes the properties and performance of the detectors of focused Cherenkov radiation that are used in several current and future particle and nuclear physics experiments. The order of presentation is guided by the physics motivation, which in turn informs the choice of technology.

Colliders as a simultaneous probe of supersymmetric dark matter and Terascale cosmology

Terascale supersymmetry has the potential to provide a natural explanation of the dominant dark matter component of the standard lambda-CDM cosmology. However once we impose the constraints on minimal supersymmetry parameters from current particle physics data, a satisfactory dark matter abundance is no longer prima facie natural. This Neutralino Tuning Problem could be a hint of nonstandard cosmology during and/or after the Terascale era. To quantify this possibility, we introduce an alternative cosmological benchmark based upon a simple model of quintessential inflation. This benchmark has no free parameters, so for a given supersymmetry model it allows an unambiguous prediction of the dark matter relic density. As a example, we scan over the parameter space of the CMSSM, comparing the neutralino relic density predictions with the bounds from WMAP. We find that the WMAP--allowed regions of the CMSSM are an order of magnitude larger if we use the alternative cosmological benchmark, as opposed to lambda-CDM. Initial results from the CERN Large Hadron Collider will distinguish between the two allowed regions.

Looking for consistency in the construction and use ofFeynman diagrams

This article describes the role of the Feynman diagramin the representation of particle interactions. Conventions forthe construction and interpretation of the diagrams aresummarized and examples of the applications of those conventionsare given. The article draws attention to the range of Feynmandiagrams in current particle physics literature and argues for amove towards consistency in their use.

The Status of the Solar Neutrino Problem

Perhaps the most outstanding discrepancy between prediction and measurements in current particle physics comes from the solar neutrino problem, in which a large deficit of high-energy solar neutrinos is observed. Many Nonstandard Solar Models have been invoked to try to reduce the predicted flux, but all have run into problems in trying to reproduce other measured parameters (e.g., the luminosity) of the Sun. Other explanations involving new physics such as neutrino decay and neutrino oscillations, etc. have also been proffered. Again, most of these explanations have been ruled out by either laboratory or astrophysical measurements. It appears that perhaps the most likely particle physics solution is that of matter enhanced neutrino oscillation, the Mikheyev-Smirnov-Wolfenstein (MSW) oscillations. Two new radiochemical gallium experiments, which have a low enough threshold to be sensitive to the dominant flux of low-energy p-p neutrinos, now also report a deficit and also favor a particle physics solution. The next generation of solar experiments promise to finally resolve the source of the ``solar neutrino problem`` by the end of this decade.