High-energy Regime Research Articles

From soft to hard radiation: the role of multiple scatterings in medium-induced gluon emissions

A proper understanding of the physics of medium-induced gluon emissions is known to be of critical importance to describe the properties of strongly interacting matter under extreme conditions. In this regard, many theoretical efforts have been directed towards obtaining analytical calculations which might help us discerning the underlying physical picture and the dominant dynamics for different regimes. These analytical approaches rely on approximations whose validity is analyzed here by comparing their results with a recently developed numerical evaluation which includes all-order resummation of multiple scatterings. More specifically, by quantitatively comparing the energy spectrum and rates, we observe that three different regimes — each with its corresponding physical picture — emerge naturally from the equations: the high-energy regime where the emission process is dominated by a single hard scattering, the intermediate-energy regime where coherence effects among multiple scatterings become fundamental, and the low-energy regime where the dynamics is again dominated by a single scattering but where one must include the suppression factor due to the probability of not having any further scatterings (which is obtained through the resummation of virtual terms).

Quantum Graphs with Vertices Violating the Time Reversal Symmetry

We discuss quantum graphs with the vertex coupling which violates the time-reversal invariance. For a simple type of this coupling in which the violation is in a sense maximum one we show that it leads to spectral properties determined in the high-energy regime by the graph topology. We illustrate this effect on examples which involve lattice graphs and loop arrays as well as finite graphs associated with Platonic solids. We also show that transport properties of such graphs may differ in the graph bulk and at the edges.

Nanoscale pattern formation on solid surfaces bombarded by two broad ion beams in the regime in which sputtering is negligible

We study nanoscale pattern formation on the surface of a solid that is bombarded with two diametrically opposed, broad ion beams for ion energies low enough that sputtering can be neglected. We focus on the case in which the angle of ion incidence is just above the threshold angle for pattern formation. The equation of motion at sufficiently long times is derived using a generalized crater function formalism. This formalism also yields expressions for the coefficients in the equation of motion in terms of crater function moments. We find that virtually defect-free ripples with a sawtooth profile can emerge at sufficiently long times. The ripples also coarsen as time passes, in contrast to the near-threshold behavior of ripples in the higher energy regime in which sputtering is significant.

Suppression of electroweak instanton processes in high-energy collisions

Electroweak instantons are a prediction of the Standard Model and have been studied in great detail in the past although they have not been observed. Earlier calculations of the instanton production cross-section at colliders revealed that it was exponentially suppressed at low energies, but may grow large at energies (much) above the sphaleron mass. Such calculations faced difficulty in the breakdown of the instanton perturbation theory in the high-energy regime. In this paper, we review the calculation for the electroweak instanton cross-section using the optical theorem, including quantum effects arising from interactions in the initial state and show that this leads to an exponential suppression of the cross-section at all energies, rendering the process unobservable.

Leading-order QED radiative corrections to timelike Compton scattering on the proton

We evaluate the leading-order QED radiative corrections to the timelike Compton scattering (TCS) process $\gamma p \to l^- l^+ p$. We study these corrections in two energy regimes using different models for the TCS amplitude. In the low-energy regime we calculate the contribution due to the proton and its lowest-energy excitation, the $\Delta(1232)$ resonance. In the high-energy near-forward kinematical regime we calculate the TCS amplitude in a handbag approach in terms of Generalized Parton Distributions (GPDs). On the level of cross sections we find the QED radiative corrections to be in the $5 -10\%$ range in the low-energy regime and around $20\%$ in the high-energy regime. We show that in both the di-lepton forward-backward asymmetry as well as in the photon beam helicity asymmetry these corrections nearly cancel out, making them gold-plated observables to extract the real and imaginary parts of the TCS amplitude. We demonstrate in particular the sensitivity of these asymmetries on GPD parameterizations for a recent CLAS12@JLab TCS experiment.

Gravitational Wave Implications for the Parity Symmetry of Gravity in the High Energy Region

Abstract Einstein's general relativity, as the most successful theory of gravity, is one of the cornerstones of modern physics. However, the experimental tests for gravity in the high energy region are limited. The emerging gravitational-wave astronomy has opened an avenue for probing the fundamental properties of gravity in a strong and dynamical field, and in particular, a high energy regime. In this work, we test the parity conservation of gravity with gravitational waves. If the parity symmetry is broken, the left- and right-handed modes of gravitational waves would follow different equations of motion, dubbed as birefringence. We perform full Bayesian inference by comparing the state-of-the-art waveform with parity violation with the compact binary coalescence data released by LIGO and Virgo collaboration. We do not find any violations of general relativity, thus constrain the lower bound of the parity-violating energy scale to be 0.09 GeV through the velocity birefringence of gravitational waves. This provides the most stringent experimental test of gravitational parity symmetry to date. We also find third generation gravitational-wave detectors can enhance this bound to GeV if there is still no violation, comparable to the current energy scale in particle physics, which indicates gravitational-wave astronomy can usher in a new era of testing the ultraviolet behavior of gravity in the high energy region.

A Note on Effects of Generalized and Extended Uncertainty Principles on Jüttner Gas

In recent years, the implications of the generalized (GUP) and extended (EUP) uncertainty principles on Maxwell–Boltzmann distribution have been widely investigated. However, at high energy regimes, the validity of Maxwell–Boltzmann statistics is under debate and instead, the Jüttner distribution is proposed as the distribution function in relativistic limit. Motivated by these considerations, in the present work, our aim is to study the effects of GUP and EUP on a system that obeys the Jüttner distribution. To achieve this goal, we address a method to get the distribution function by starting from the partition function and its relation with thermal energy which finally helps us in finding the corresponding energy density states.

Baryon production probability via the nuclear configurational entropy

We study the net-baryon production at forward rapidities within the Color Glass Condensate paradigm. At high energy regime, the leading baryon production mechanism is shown to change from recombination to independent fragmentation. The nuclear configurational entropy (NCE) constructed upon forward scattering amplitudes allows to predict the two free parameters that govern the anomalous dimension of the target gluon distribution. The global minimum of the NCE indicates a point of stability in pp/pA/AA collisions at LHC energies, corroborating and matching RHIC data for hadron spectra measured in pp and dAu collisions at RHIC energies, with accuracy between 1.2 and 1.8%, respectively, for the two free parameters.

A Two-zone Photohadronic Interpretation of the EHBL-like Behavior of the 2016 Multi-TeV Flares of 1ES 1959+650

Abstract The high-energy-peaked blazar 1ES 1959+650 is a well-known and well-studied nearby blazar that has undergone several episodes of multi-TeV flaring. In 2002 for the first time an orphan TeV flare was observed from this blazar. During a multiwavelength campaign from 2016 April 29 to November 21, MAGIC telescopes observed multi-TeV flarings during the nights of 2016 June 13 and 14 and July 1 when the position of the synchrotron peak was found to be above 1017 Hz. Also observed was that the second peak of the spectral energy distribution shifted toward higher energy and exhibited extreme HBL-like behavior. The photohadronic model, which is very successful at explaining the multi-TeV flaring from many high energy blazars, including 1ES 1959+650, is applied to study the flaring events of 2016. It is observed that the photohadronic model is unable to explain the observed spectra. Here, we use a two-zone photohadronic model to explain the observed spectra. We clearly demonstrate that the low energy regime (zone-1) of the spectra corresponds to the standard flaring events of the high energy blazar and the high energy regime (zone-2) of the spectra is solely due to the extreme nature of the flaring events. Our two-zone photohadronic model explains the multi-TeV flaring events observed by MAGIC telescopes very well.

Red-to-Blue Photon Upconversion Enabled by One-Dimensional CdTe Nanorods

Photon upconversion via triplet–triplet annihilation creating light in the high-energy regime of the visible spectrum could prove particularly useful in applications such as photocatalysis. Quantum...

Hydrodynamic computations of high-power laser drives generating metal ejecta jets from surface grooves

Understanding dynamic fragmentation in shock-loaded metals and predicting properties of the resulting ejecta are of considerable importance for both basic and applied science. The nature of material ejection has been shown to change drastically when the free surface melts on compression or release. In this work, we present hydrodynamic simulations of laser-driven microjetting from micron-scale grooves on a tin surface. We study microjet formation across a range of shock strengths from drives that leave the target solid after release to drives that induce shock melting in the target. The shock-state particle velocity (Up) varies from 0.3 to 3 km/s and the shock breakout pressure is 3–120 GPa. The microjet tip velocity is 1–8 km/s and the free-surface velocity varies from 0.1 to 5 km/s. Two tin equations of state are examined: a “soft” model (LEOS 501) where the target melts for Up>1 km/s and a more detailed multiphase model (SESAME 2161) that melts for Up>1.4 km/s. We use these two models to examine the influence of phase change and the choice of the material model on microjet formation and evolution. We observe in our computational results that jet formation can be classified into three regimes: a low-energy regime where material strength affects jet formation, a moderate-energy regime dominated by the changing phase of tin material, and a high-energy regime where results are insensitive to the material model and jet formation is described by an idealized steady-jet theory. Using an ensemble of 2D simulations, we show that these trends hold across a wide range of drive energies and groove angles.

From period to quasiperiod to chaos: A continuous spectrum of orbits of charged particles trapped in a dipole magnetic field.

Via evaluation of the Lyapunov exponent, we report the discovery of three prominent sets of phase space regimes of quasiperiodic orbits of charged particles trapped in a dipole magnetic field. Besides the low energy regime that has been studied extensively and covers more than ∼10% in each dimension of the phase space of trapped orbits, there are two sets of high energy regimes, the largest of which covers more than ∼4% in each dimension of the phase space of trapped orbits. Particles in these high-energy orbits may be observed in space and be realized in plasma experiments on the earth.

The conundrum of biont-free substrates on a high-energy continental shelf: Burial and scour on Nantucket Shoals, Great South Channel

A survey of the adjacent waters east of Nantucket, Massachusetts provided an opportunity to evaluate the epibiota attached to cobbles, rocks, boulders, and Atlantic surfclam shell in a region of high tidal current velocity and sand scour where burial, exhumation, and scour may limit epibiont coverage on exposed, and thus otherwise highly preferred for attachment, substrates. Such conditions may confute the expectation that substrate complexity always adds significantly to ecosystem value by expanding the range of habitat options and consequently increasing species richness and trophic linkages. Sedimentary particles potentially providing good attachment substrate for erect sessile epibiota included surfclam shells, abundant at many locations, cobbles, nearly ubiquitous, rocks, routinely encountered, and occasional boulders. The attached epibiota fell into three categories based on their biases for particle types. Some preferred the largest particles or evidence of their occupation was best preserved on these particles: these included sponges, mussels, and barnacles and their scars. Some preferred intermediate and smaller terrigenous particles; these included tunicates and encrusting bryozoans. Some preferred surfclam shells, namely the slipper shells and erect hydroids. Slow-growing attached epibionts were exceedingly rare and all soft-bodied attached epibionts were rare. Only barnacles and their taphonomic scars and hydroids were common. The frequency of barnacle scars relative to intact barnacles suggests sediment scour under a high-flow regime. Mussels were rarely attached to larger sedimentary particles such as cobbles and rocks, though commonly occurring locally as mussel beds on sand and pebble, further supporting the ephemerality of exposed unscoured attachment sites. The absence of attached epibionts demonstrates that edaphic processes minimize the importance of cobbles, rocks, boulders, and shells in community structure in some subtidal high-energy regimes, defying expectations from their contribution to substrate complexity. Their apparent contribution to habitat complexity belies their resultant much more minor role in determining community composition, thereby limiting their ecosystem value.

Monolithic integration of mesoporous germanium: A step toward high-performance on-chip anode

Advanced energy storage systems are one of the essential pillars for accelerating development of the cutting-edge technologies, including Internet of things and grid energy storage. Microbatteries with high power and energy density levels are then required and germanium, despite its relatively high cost, is an attractive candidate in this field due to its high specific capacity. This study is the first report of a monolithic mesoporous germanium (mpGe) and graphene-coated mesoporous germanium nanocomposite (GPGNC) as anodes for Li-ion battery within an on-chip architecture. In this configuration, the sample substrate is used as the current collector while the porous part acts as the active material. GPGNC exhibits an outstanding electrochemical performance at high areal capacity (1 mAh cm−2) and offers a high capacity retention at slow (C/5) and medium (2C) discharge rates. Moreover, no capacity fading is observed during 1000 cycles at C/5 rate with Coulombic efficiency of 98.9 %. High rate capacity application has also been investigated and a 4000 cycle lifetime at 5 mA cm−2 discharge current during 1 min was demonstrated. Our findings evidenced superior performance of on-chip anodes based on mesoporous Ge at high energy and high power density regimes.

High-energy multidimensional solitary states in hollow-core fibres

Multidimensional solitary states (MDSS)—self-sustained wavepackets—have attracted renewed interest in many different fields of physics. They are of particular importance in nonlinear optics, especially for the nonlinear propagation of ultrashort pulses in multimode fibres, which contain rich spatiotemporal intermodal interactions and dynamics, albeit often in an unstable manner. Here, we report the observation of the formation of highly stable multidimensional solitary states in a molecular gas-filled large-core hollow-core fibre. We experimentally and numerically demonstrate the creation of MDSS by multimillijoule, subpicosecond near-infrared pulses and the underlying physics. We find that the MDSS have a broadband redshifted spectra with an uncommon negative quadratic spectral phase at the output of the hollow-core fibre, originating from Raman enhancement due to the strong intermodal nonlinear interactions. The spatial and temporal localization of MDSS enables the compression of the broadened pulses at the output to 10.8 fs by simple linear propagation in a piece of fused silica. The high spatiotemporal quality of MDSS is further verified by high-harmonic generation. Our results present new opportunities for studying multimodal spatiotemporal dynamics in the high-energy regime. This work also presents a route toward a new class of compact, tunable and high-energy spatiotemporally engineered coherent light sources based on picosecond ytterbium technology. The formation of multidimensional solitary states through the nonlinear propagation of high-energy pulses in a molecular gas-filled large-core hollow-core fibre is demonstrated, offering new opportunities for studying multimodal spatiotemporal dynamics in the high-energy regime.

A Two-zone Photohadronic Scenario for EHBL-like Behavior of Mrk 501

Abstract Major outbursts have been observed from the well known high-energy-peaked blazar Markarian 501 since its discovery in 1996. Two episodes of very-high-energy gamma-ray flaring events during 2005 May–July and 2012 June are of special significance, as the source exhibited extreme HBL-like behavior. The successful standard photohadronic model does not adequately explain these extraneous behaviors. We propose a two-zone photohadronic scenario to overcome this problem. In this picture, the low-energy regime (zone-1) of the spectrum follows the standard photohadronic interpretation, while the high-energy regime (zone-2) of the spectrum is new, with a spectral index δ 2 ≥ 3.1, which is solely due to the extreme nature of the flaring event. We also estimate the bulk Lorentz factor corresponding to these extreme flaring events. By analyzing many flaring events before and after these extreme events we argue that the extreme HBL-like events are transient and may repeat in the future.

Investigation of thermal residual stresses during laser ablation of tantalum carbide coated graphite substrates using micro-Raman spectroscopy and COMSOL multiphysics

Laser ablation of high-temperature ceramic coatings results in thermal residual stresses due to which the coatings fail by cracking and debonding. Hence, the measurement of such residual stresses during laser ablation process holds utmost importance from the view of performance of coatings in extreme conditions. The present research aims at investigating the effect of laser parameters such as laser pulse energy, scanning speed and line spacing on thermal residual stresses induced in tantalum carbide-coated graphite substrates. Residual stresses were measured using micro-Raman spectroscopy and correlated with Raman peak shifts. Transient thermal analysis was performed using COMSOL Multiphysics to model the single ablated track and residual stresses were reported at low, moderate and high pulse energy regimes. The results showed that the initial laser conditions caused higher tensile residual stresses. Moderate pulse energy regime comprised higher compressive residual stresses due to off centre overlapping of the laser pulses. Higher pulse energy (250 μJ), higher scanning speed (1000 mm/s) and moderate line spacing (20 μm) caused accumulation of tensile residual stresses during the final stage of laser ablation. The deviation of experimental residual stresses from COMSOL numerical model was attributed to unaccounted additional stresses induced during thermal spraying process and deformation potentials in the numerical model.

Exchange field effects on the electronic properties of heterostructured ferromagnetic/topological crystalline insulator

Abstract In this paper, the exchange field effects are theoretically investigated to generate the mass in ferromagnetic/topological crystalline insulator SnTe heterostructure. The Dirac theory of exchange field-induced system predicts the anisotropic gaps in both low- and high-energy regimes. At small momenta, the group velocity is anisotropic, coinciding with orientation-dependent Fermi velocities, however; it increases (decreases) when the magnetization vector is parallel (antiparallel) to the host spin direction. Further, we found that the effective mass is anisotropic as well and y-direction is responsible for the heavy-mass band around Dirac points. Moreover, the proximity coupling leads to the switching of the effective mass sign at small momenta due to the band gap opening and concavity changing of bands. Additionally, a decreasing behavior for effective mass with exchange field strength is seen independently of the direction.

First-principles investigations of electronic structures and optical spectra of wurtzite and sphalerite types of ZnO1-xSx (x=0, 0.25, 0.50, 0.75 &1) alloys

Alloying of the zinc oxide (ZnO) with sulfur (S) chalcogen reveals vivid modifications of its electronic and optical properties driven by the dramatic restructuring of electronic structure. Here, we systematically executed mutual alloying of ZnO and ZnS in two different structural phases namely the wurtzite and sphalerite phases. Evolution in the physical properties of the designed ZnO1-xSx alloys for the compositions, x = 0, 0.25, 0.50, 0.75 and 1 has been comprehensively examined by using full-potential linearized augmented-plane-wave plus local orbital approach within density functional theory. It is observed that the replacement of the Oxygen by Sulfur atoms significantly affects the band-structure profiles of ZnO1-xSx alloys in both wurtzite and sphalerite geometries. Furthermore, by increasing the S contents in ZnO1-xSx alloys, the conduction band minimum is found to be moved in the upward direction resulting in enhancement of the bandgaps. The electronic bandgaps of ZnO1-xSx alloys were enhanced from 2.65 eV to 3.68 eV in wurtzite and from 2.50 eV to 3.60 eV in sphalerite phase. Similarly, the imaginary parts of the dielectric function of ZnO1-xSx move towards a high energy regime with an increase in S composition, which resulted in a blueshift in their absorption edges. Our results are found well-matching with available theoretical and experimental results. The variation in the energy bandgaps and optical properties makes the S-rich ZnO a promising candidate for ultraviolet photoelectronic devices.

Quantum walks and Dirac cellular automata on a programmable trapped-ion quantum computer

The quantum walk formalism is a widely used and highly successful framework for modeling quantum systems, such as simulations of the Dirac equation, different dynamics in both the low and high energy regime, and for developing a wide range of quantum algorithms. Here we present the circuit-based implementation of a discrete-time quantum walk in position space on a five-qubit trapped-ion quantum processor. We encode the space of walker positions in particular multi-qubit states and program the system to operate with different quantum walk parameters, experimentally realizing a Dirac cellular automaton with tunable mass parameter. The quantum walk circuits and position state mapping scale favorably to a larger model and physical systems, allowing the implementation of any algorithm based on discrete-time quantum walks algorithm and the dynamics associated with the discretized version of the Dirac equation.