TeV Energies Research Articles

Plasma density transition-based electron injection in laser wake field acceleration driven by a flying focus laser

By using a high-intensity flying focus laser, the dephasingless [Phys. Rev. Lett. 124 134802 (2020)] or phase-locked [Nat. Photon. 14 475 (2020)] laser wakefield acceleration (LWFA) can be realized, which may overcome issues of laser diffraction, pump depletion, and electron dephasing which are always suffered in usual LWFA. The scheme thus has the potentiality to accelerate electrons to TeV energy in a single acceleration stage. However, the controlled electron injection has not been self-consistently included in such schemes. Only external injection was suggested in previous theoretical studies, which requires other accelerators and is relatively difficulty to operate. Here, we numerically study the actively controlled density transition injection in phase-locked LWFA to get appropriate density profiles for amount of electron injection. The study shows that compared with LWFA driven by lasers with fixed focus, a larger plasma density gradient is necessary. Electrons experience both transverse and longitudinal loss during acceleration due to the superluminal group velocity of the driver and the variation of the wakefield structure. Furthermore, the periodic deformation and fracture of the flying focus laser in the high-density plasma plateau make the final injected charge also depend on the beginning position of the density downramp. Our studies show a possible way for amount of electron injection in LWFA driven by flying focus lasers.

Precision μ+μ+ and μ+e− elastic scatterings

Abstract The expected measurement precisions of elastic scattering cross sections are estimated for μ+μ+ and μ+e− colliders, which have recently been proposed as future realistic possibilities (μTRISTAN). Compared with contributions from possible new physics represented by higher-dimensional operators, we find that the measurements at a TeV energy μ+μ+ collider can probe the scale of new physics up to O(100) TeV. A μ+e− collider for the Higgs boson factory can also improve the electroweak precision test. For those studies, we assume the expected integrated luminosity at μTRISTAN, Lint = 120 fb−1 (μ+μ+) and 1 ab−1 (μ+e−).

Gamma‐ray production in supermassive black hole binary OJ 287

AbstractOJ 287 is one of the most studied BL Lac objects with very long optical measurements whose spectrum has been well measured through radio to X‐ray band. The most outstanding characteristic of OJ 287 is its 12‐year period, which is discovered in the optical range and has also been confirmed in the X‐ray band. OJ 287 is supposed to be a binary black hole system in which a secondary black hole passes the accretion disk of the primary black hole and produces two impact flashes per period. It has also been proposed to be a GeV–TeV source. Observations of OJ 287 in the GeV–TeV energy range reveal the variable γ‐ray connected with the flare activity of this object. The spectral energy distributions of blazars consist of two broad peaks. The first, lower frequency peak is due to the synchrotron emissions of relativistic electrons in the jet. Leptonic and hadronic emission mechanisms are considered to describe the second, higher frequency spectrum part. The inverse Compton emissions of the same electrons (synchrotron self‐Compton model) or combined with an external Compton mechanism are considered in the leptonic scenario. The last one supposes the existence of the external to jet photon cloud. The high‐energy spectrum part is also supposed to be generated due to the acceleration of the cosmic ray hadrons in shock produced by outflow, which expands and then collides with the wind of the primary black hole. The detection of GeV–TeV energy fluxes can help find the parameters of the configuration of the two‐black hole system.

A possible explanation of the TeV emission from the pulsar wind nebula HESS J1825-137

ABSTRACT Pulsar wind nebula (PWN) HESS J1825-137 is one of the largest and brightest gamma-ray sources in Milky Way. It was found that the morphology of the nebula strongly depends on energy and the photon spectrum varies obviously with distance from the pulsar in the >0.1 TeV energy band. In the frame of a spatially-dependent particle transport model, we investigate the TeV gamma-ray observed features of HESS J1825-137 by using the Markov chain Monte Carlo method. Our results are as follows: (i) the observed features can be reasonably explained by the competition between the transport (advection and diffusion) and energy cooling losses (adiabatic, synchrotron, and inverse Compton) of the high energy electrons, and that a parameter ξ ≡ τp/τC is introduced to describe this competition, which is the function of electron energy and position within the nebula, where τp and τC are total transport and energy cooling timescales, respectively; (ii) for the high energy electrons (Ee > 0.1 TeV) within the nebula, the particle diffusion dominates over its advection, and the radiative cooling mostly dominates over adiabatic cooling; and (iii) the change of the radial extent with photon energy Eγ can be expressed as $R\propto E^{-\beta }_\gamma$, where the index β is a function of Eγ and the Klein−Nishina effect has a very important role for the variation of β with Eγ. From the modelling results, the initial rotation period, braking index, and age of the pulsar are predicted to be 12.16 ms, 1.79, and 44 kyr, respectively.

Transverse Momentum Dependence on Fourier Elliptic and Triangular Flow Harmonics in Mid-Central Pbpb Collisions at

We have collected particle collision data from the experiment using CMS apparatus, where we studied charged ions in the nucleus-to-nucleus collision’s PbPb branch in Pb at the 2.76 TeV energy scale. So far for the present work, we report the anisotropy of the thermal observational flux in lead-lead nucleon collisions at sqrt = 2.76 TeV. We observed that the collisions produced a large ion azimuth angle ranging from −π to π radian and a pseudo-conductance ranging from -2.6 to 2.6. In this work, we report the correlation function of transverse momentum, Pt , Δη, and ΔΦ over a wide range of centroids. When the transverse momentum is about 1-2 GeV/c and Δη is in range -1 to 1, we observe a jet peak in the η and Φ correlation plot as the centrality increases. In the case of ν 2, which is an elliptic current signal, we measured it with a 4-part correlation method in the 40-50% centrality class. Asymptotic angular correlations in the far range have been studied by Fourier decomposition on the product of anisotropies when the cross-correlation is equal to 3-3.5 GeV/c. The obtained Fourier coefficients are factorized into the singular product of -ion Φ anisotropies. The assumptions of the hydrodynamic model with the shear viscosity correlation increase accordingly.

Assessing aerosol induced errors in Monte Carlo based air-shower reconstruction for atmospheric Cherenkov detectors

Aerosol levels influence the wavelength dependent transmission properties of the atmosphere. Variations in aerosol levels therefore affect the amount of Cherenkov light from air-showers that can reach an atmospheric Cherenkov detector. As the amount of detected Cherenkov light is directly related to a primary shower particle’s energy, deviations between actual and assumed atmospheric transmission properties yield errors in reconstructed particle energies as well as energy axes of instrument response functions. In this work, a scheme is presented to assess this influence and potentially reduce related errors in the air-shower reconstruction. The proposed scheme relies on estimations or measurements of the aerosol optical depth and atmospheric density profile which are then used in radiative transfer simulations to generate atmospheric transmission profiles. As the scheme furthermore uses detector specific quantum efficiencies and generalised shower evolution models, it does not rely on detailed Monte Carlo simulations for the different atmospheric conditions but only on the transmission profile which the initial shower reconstruction algorithm is based on. The approach is derived and presented on the example of the H.E.S.S. experiment which employs imaging atmospheric Cherenkov telescopes in the Khomas Highland of Namibia to detect gamma rays in the GeV to TeV energy range.

MeV–GeV Gamma-Ray Emission from SNR G327.1–1.1 Discovered by the Fermi-LAT

We report the discovery of MeV–GeV γ-ray emission by the Fermi-LAT positionally coincident with the TeV pulsar wind nebula (PWN) HESS J1554–550 within the host supernova remnant (SNR) G327.1–1.1. The γ-ray emission is point-like and faint but significant (>4σ) in the 300 MeV–2 TeV energy range. We report here the Fermi-LAT analysis of the observed γ-ray emission followed by a detailed multiwavelength investigation to understand the nature of the emission. The central pulsar powering the PWN within G327.1–1.1 has not been detected in any wave band; however, it is likely embedded within the X-ray nebula, which is displaced from the center of the radio nebula. The γ-ray emission is faint and therefore a pulsation search to determine if the pulsar may be contributing is not feasible. Prior detailed multiwavelength reports revealed an SNR system that is old, τ ∼ 18,000 yr, where the interaction of the reverse shock with the PWN is underway or has recently occurred. We find that the γ-ray emission agrees remarkably well with a detailed broadband model constructed in a prior report based on independent hydrodynamical and semianalytic simulations of an evolved PWN. We further investigate the physical implications of the model for the PWN evolutionary stage incorporating the new Fermi-LAT data and attempt to model the distinct particle components based on a spatial separation analysis of the displaced PWN counterparts.

A test of spatial coincidence between CHIME FRBs and IceCube TeV energy neutrinos

We search for a spatial association between the Canadian Hydrogen Mapping Intensity Experiment (CHIME) FRBs and IceCube neutrinos detected in the TeV energy range, by counting the total number of neutrino-FRB pairs with angular separations of <3 degrees, as well as within the observed neutrino error circle. This number constitutes the total signal events, which is then compared to the total background, corresponding to the null hypothesis of no spatial association. The background was obtained from the total neutrino-FRB matches in off-source angular windows with the same solid angle as the signal window. We do not find any statistically significant excess compared to the background. Therefore, we conclude that there is no evidence for an angular correlation between the IceCube neutrinos in the TeV energy range and CHIME FRBs. For each of these searches, we report 90% Bayesian credible interval upper limits on the observed FRB-induced neutrinos.

The steady-state multi-TeV diffuse γ-ray emission predicted with galprop and prospects for the Cherenkov Telescope Array

ABSTRACT Cosmic rays (CRs) interact with the diffuse gas, radiation, and magnetic fields in the interstellar medium (ISM) to produce electromagnetic emissions that are a significant component of the all-sky flux across a broad wavelength range. The Fermi–Large Area Telescope (LAT) has measured these emissions at GeV γ-ray energies with high statistics. Meanwhile, the high-energy stereoscopic system (H.E.S.S.) telescope array has observed large-scale Galactic diffuse emission in the TeV γ-ray energy range. The emissions observed at GeV and TeV energies are connected by the common origin of the CR particles injected by the sources, but the energy dependence of the mixture from the general ISM (true ‘diffuse’), those emanating from the relatively nearby interstellar space about the sources, and the sources themselves, is not well understood. In this paper, we investigate predictions of the broad-band emissions using the galprop code over a grid of steady-state 3D models that include variations over CR sources, and other ISM target distributions. We compare, in particular, the model predictions in the very-high energy ( VHE; ≳100 GeV) γ-ray range with the H.E.S.S. Galactic plane survey (HGPS) after carefully subtracting emission from catalogued γ-ray sources. Accounting for the unresolved source contribution, and the systematic uncertainty of the HGPS, we find that the galprop model predictions agree with lower estimates for the HGPS source-subtracted diffuse flux. We discuss the implications of the modelling results for interpretation of data from the next generation Cherenkov Telescope Array (CTA).

First search for magnetic monopoles through the Schwinger mechanism

Magnetic monopoles are hypothetical fundamental particles predicted in several theories beyond the standard model, however they have never been experimentally detected. The Schwinger mechanism predicts that an extremely strong magnetic field would produce isolated magnetic charges, if they exist. Looking for the existence of magnetic monopoles via the Schwinger mechanism had not been attempted before, but it is advantageous, owing to the possibility of calculating its rate through semi-classical techniques without perturbation theory. This paper focuses on the first search for magnetic monopoles produced by the Schwinger mechanism in heavy-ion collisions. It was carried out by the MoEDAL experiment, whose trapping detectors were exposed to 0.235 nb−1 of Pb-Pb collisions with 5.02 TeV energy per collision at the LHC, that provided the strongest known magnetic fields in the universe. A superconducting quantum interference device magnetometer scanned these detectors for the presence of magnetic charge. Magnetic monopoles with 1, 2 and 3 Dirac charges and masses up to 75 GeV were excluded by the analysis. This analysis, which has been published in the journal Nature, provided a lower mass limit for finite-size magnetic monopoles from a collider search and greatly extended previous mass bounds.

Assembly and test of prototype scintillator tiles for the plastic scintillator detector of the High Energy Cosmic Radiation Detection (HERD) facility

Satellite experiments for gamma-ray and cosmic-ray detection employ plastic scintillators to discriminate charged from neutral particles in order to correctly identify gamma-rays and charged nuclei. The High Energy Cosmic Radiation Detection (HERD) facility will be among these experiments, to be installed onboard the future Chinese Space Station (CSS), to detect cosmic-rays and gamma-rays up to TeV energies. The plastic scintillator detector (PSD) will consist of scintillator tiles or bars coupled to Silicon Photomultipliers (SiPMs). To discriminate gamma-rays from charged particles and measure the ion charge up to iron nuclei a wide dynamic range is required, from few tens up to thousands of photoelectrons. We have equipped a plastic scintillator tile prototype with SiPMs produced by Hamamatsu and AdvanSiD and coupled their analog signals to the DT5550W board based on the CITIROC ASIC, produced by CAEN SpA. The CITIROC ASIC allows both the formation of a fast trigger with a configurable threshold and the digitization of analog waveforms after a preamplification and shaping stage along two paths with different gain settings. The performance of our prototype will be shown.

Neutrino detection without neutrino detectors: Discovering collider neutrinos at FASER with electronic signals only

The detection of collider neutrinos will provide new insights about neutrino production, propagation, and interactions at TeV energies, the highest human-made energies ever observed. During Run 3 of the LHC, the FASER experiment is expected to detect roughly $10^4$ collider neutrinos using its emulsion-based neutrino detector FASER$\nu$. In this study, we show that, even without processing the emulsion data, low-level input provided by the electronic detector components of FASER and FASER$\nu$ will be able to establish a $5\sigma$ discovery of collider neutrinos with as little as $5~\text{fb}^{-1}$ of integrated luminosity. These results foreshadow the possible early discovery of collider neutrinos in LHC Run 3.

Investigating color screening in proton-nucleus collisions with complex potentials* *Supported by the National Natural Science Foundation of China (NSFC) (12175165, 11705125); S.S. acknowledges support from U.S. Department of Energy, Office of Science, Office of Nuclear Physics, (DE-FG88ER40388); X.D acknowledges support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through the CRC-TR 211 'Strong-interaction matter under extreme conditions’– project number 315477589

Color screening and parton inelastic scattering modify the heavy-quark antiquark potential in mediums consisting of particles from quantum chromodynamics (QCD), leading to the suppression of quarkonium production in relativistic heavy-ion collisions. Owing to the small charm/anti-charm () pair production number in proton-nucleus (pA) collisions, the correlation between different pairs is negligible, which makes the Schrödinger equation viable for tracking the evolution of only one pair. We employ the time-dependent Schrödinger equation with an in-medium potential to study the evolution of charmonium wave functions in a hydrodynamic-like QCD medium produced in pA collisions. We explore different parametrizations of real and imaginary parts of the potential and calculate the nuclear modification factors () of and in TeV energy p-Pb collisions at the Large Hadron Collider (LHC). Comparing strong and weak screening scenarios with experimental data in this approach, we arrive at the conclusion that color screening is weak at temperatures close to the deconfined phase transition. Moreover, the imaginary part of the potential is crucial in describing the experimental data, which is consistent with widely studied semi-classical approaches, where dissociation rates are essential.

Future projections on the anomalous WWγγ couplings in hadron–hadron interactions at the FCC-hh

We carry out a study in the approach of a dimension-eight effective field theory on the anomalous quartic WWγγ couplings that arise from the process pp → Wγγ at the Future Circular Collider-hadron hadron (FCC-hh). The process is sensitive to the WWγγ vertex, and future projections on the anomalous f M,i /Λ4 and f T,j /Λ4 couplings can be put by measurements of Wγγ production. We illustrate the physics opportunities and reach of the FCC-hh operating for a high integrated luminosity scenario of of proton–proton collisions at a center-of-mass energy of TeV and systematic uncertainties of δ sys = 0%, 3%, 5%, 10%. Production cross-sections of the signal and the sensitivity constraints on the anomalous f M,i /Λ4 and f T,j /Λ4 couplings at 95% C.L. are identified through the leptonic and hadronic decay modes of the W-boson. The FCC-hh sensitivity on these anomalous couplings is expected might reach up to the order of magnitude . These sensitivity perspectives indicate that the pp → Wγγ channel at the FCC-hh has a greater potential to search for the anomalous quartic WWγγ couplings and to search for new physics than present colliders.

First Measurement of the Z→μ^{+}μ^{-} Angular Coefficients in the Forward Region of pp Collisions at sqrt[s]=13 TeV.

The first study of the angular distribution of μ^{+}μ^{-} pairs produced in the forward rapidity region via the Drell-Yan reaction pp→γ^{*}/Z+X→ℓ^{+}ℓ^{-}+X is presented, using data collected with the LHCb detector at a center-of-mass energy of 13TeV, corresponding to an integrated luminosity of 5.1 fb^{-1}. The coefficients of the five leading terms in the angular distribution are determined as a function of the dimuon transverse momentum and rapidity. The results are compared to various theoretical predictions of the Z-boson production mechanism and can also be used to probe transverse-momentum-dependent parton distributions within the proton.

Evidence for PeV Proton Acceleration from Fermi-LAT Observations of SNR G106.3+2.7.

The existence of a "knee" at energy ∼1 PeV in the cosmic-ray spectrum suggests the presence of Galactic PeV proton accelerators called "PeVatrons." Supernova remnant (SNR) G106.3+2.7 is a prime candidate for one of these. The recent detection of very high energy (0.1-100TeV) gamma rays from G106.3+2.7 may be explained either by the decay of neutral pions or inverse Compton scattering by relativistic electrons. We report an analysis of 12years of Fermi-LAT gamma-ray data that shows that the GeV-TeV gamma-ray spectrum is much harder and requires a different total electron energy than the radio and x-ray spectra, suggesting it has a distinct, hadronic origin. The nondetection of gamma rays below 10GeV implies additional constraints on the relativistic electron spectrum. A hadronic interpretation of the observed gamma rays is strongly supported. This observation confirms the long-sought connection between Galactic PeVatrons and SNRs. Moreover, it suggests that G106.3+2.7 could be the brightest member of a new population of SNRs whose gamma-ray energy flux peaks at TeV energies. Such a population may contribute to the cosmic-ray knee and be revealed by future very high energy gamma-ray detectors.

Tau depolarization at very high energies for neutrino telescopes

The neutrino interaction length scales with energy, and becomes comparable to Earth's diameter above 10's of TeV energies. Over terrestrial distances, the tau's short lifetime leads to an energetic regenerated tau neutrino flux, tau neutrino to tau to tau neutrino, within the Earth. The next generation of neutrino experiments aim to detect ultra-high energy neutrinos. Many of them rely on detecting either the regenerated tau neutrino, or a tau decay shower. Both of these signatures can be affected by the polarization of the tau through the energy distribution of the secondary particles produced from the tau's decay. While taus produced in weak interactions are nearly 100 percent polarized, it is expected that taus experience some depolarization due to electromagnetic interactions in the Earth. In this paper, for the first time we quantify the depolarization of taus in electromagnetic energy loss. We find that tau depolarization has only small effects on the final energy of tau neutrinos or taus produced by high energy tau neutrinos incident on the Earth. Tau depolarization can be directly implemented in Monte Carlo simulations such as nuPyProp and TauRunner.

First predicted cosmic ray spectra, primary-to-secondary ratios, and ionization rates from MHD galaxy formation simulations

ABSTRACT We present the first simulations evolving resolved spectra of cosmic rays (CRs) from MeV–TeV energies (including electrons, positrons, (anti)protons, and heavier nuclei), in live kinetic-magnetohydrodynamics galaxy simulations with star formation and feedback. We utilize new numerical methods including terms often neglected in historical models, comparing Milky Way analogues with phenomenological scattering coefficients ν to Solar-neighbourhood [Local interstellar medium (LISM)] observations (spectra, B/C, e+/e−, $\mathrm{\bar{p}}/\mathrm{p}$, 10Be/9Be, ionization, and γ-rays). We show it is possible to reproduce observations with simple single-power-law injection and scattering coefficients (scaling with rigidity R), similar to previous (non-dynamical) calculations. We also find: (1) The circumgalactic medium in realistic galaxies necessarily imposes an $\sim 10\,$ kpc CR scattering halo, influencing the required ν(R). (2) Increasing the normalization of ν(R) re-normalizes CR secondary spectra but also changes primary spectral slopes, owing to source distribution and loss effects. (3) Diffusive/turbulent reacceleration is unimportant and generally sub-dominant to gyroresonant/streaming losses, which are sub-dominant to adiabatic/convective terms dominated by $\sim 0.1-1\,$ kpc turbulent/fountain motions. (4) CR spectra vary considerably across galaxies; certain features can arise from local structure rather than transport physics. (5) Systematic variation in CR ionization rates between LISM and molecular clouds (or Galactic position) arises naturally without invoking alternative sources. (6) Abundances of CNO nuclei require most CR acceleration occurs around when reverse shocks form in SNe, not in OB wind bubbles or later Sedov–Taylor stages of SNe remnants.

First Search for Exclusive Diphoton Production at High Mass with Tagged Protons in Proton-Proton Collisions at sqrt[s]=13 TeV.

A search for exclusive two-photon production via photon exchange in proton-proton collisions, pp→pγγp with intact protons, is presented. The data correspond to an integrated luminosity of 9.4 fb^{-1} collected in 2016 using the CMS and TOTEM detectors at a center-of-mass energy of 13TeV at the LHC. Events are selected with a diphoton invariant mass above 350GeV and with both protons intact in the final state, to reduce backgrounds from strong interactions. The events of interest are those where the invariant mass and rapidity calculated from the momentum losses of the forward-moving protons match the mass and rapidity of the central, two-photon system. No events are found that satisfy this condition. Interpreting this result in an effective dimension-8 extension of the standard model, the first limits are set on the two anomalous four-photon coupling parameters. If the other parameter is constrained to its standard model value, the limits at 95% confidence level are |ζ_{1}|<2.9×10^{-13} GeV^{-4} and |ζ_{2}|<6.0×10^{-13} GeV^{-4}.

The contribution of Galactic TeV pulsar wind nebulae to Fermi large area telescope diffuse emission

The large-scale diffuse γ − ray flux observed by Fermi Large Area Telescope (Fermi-LAT) in the 1–100 GeV energy range, parameterized as ∝ E−Γ, has a spectral index Γ that depends on the distance from the Galactic center. This feature, if attributed to the diffuse emission produced by cosmic rays interactions with the interstellar gas, can be interpreted as the evidence of a progressive cosmic ray spectral hardening towards the Galactic center. This interpretation challenges the paradigm of uniform cosmic rays diffusion throughout the Galaxy. We report on the implications of TeV Pulsar Wind Nebulae observed by the High Energy Stereoscopic System (H.E.S.S.) Galactic Plane Survey in the 1–100 TeV energy range for the interpretation of Fermi-LAT data. We argue that a relevant fraction of this population cannot be resolved by Fermi-LAT in the GeV domain providing a relevant contribution to the large-scale diffuse emission, ranging within ~4%–40% of the total diffuse γ-ray emission in the inner Galaxy. This additional component may account for a large part of the spectral index variation observed by Fermi-LAT, weakening the evidence of cosmic ray spectral hardening in the inner Galaxy.