Design of hadronic calorimeter for DarkSHINE experiment

The sensitivity of the dark photon search through invisible decay final states in low-background experiments relies sig-nificantly on the neutron and muon veto efficiencies,which depend on the amount of material used and the design of the detector geometry.This paper presents the optimized design of the hadronic calorimeter(HCAL)used in the DarkSHINE experiment,which is studied using a GEANT4-based simulation framework.The geometry is optimized by comparing a traditional design with uniform absorbers to one that uses different thicknesses at different locations on the detector,which enhances the efficiency of vetoing low-energy neutrons at the sub-GeV level.The overall size and total amount of material used in the HCAL are optimized to be lower,owing to the load and budget requirements,whereas the overall performance is studied to satisfy the physical objectives.

Performance of AC-LGAD strip sensors designed for the DarkSHINE experiment

The DarkSHINE experiment proposes a novel approach to single-electron-on-fixed-target exploration that focuses on the search for dark photons through their invisible decay into dark matter particles.Central to this initiative is an advanced tracking detector designed to achieve exceptional sensitivity in the detection of light dark matter candidates.This study evaluates the performance of several prototype AC-coupled low-gain avalanche diode(AC-LGAD)strip sensors specifically developed for the DarkSHINE tracking detector.The electrical properties of the sensors from two batches of wafers with different n^(+)doses are thoroughly evaluated.Spatial and temporal resolutions are measured using an infrared laser source.The spatial resolutions range from 6.5 to 8.2μm and from 8.8 to 12.3μm for the sensors from two distinct dose batches,each with a 100μm pitch size.Furthermore,the sensors demonstrate time resolutions of 8.3 and 11.4 ps,underscoring the potential of AC-LGAD technology in enhancing the performance of the DarkSHINE tracking detector.

Insight-HXMT Research Progress Since 2023

Since the launch in June 2017,Insight-HXMT has been in service smoothly in orbit and particularly productive in 2023 and 2024.Among a total number of 238 papers published so far based on Insight-HXMT data,63 were published in 2023,and 32 in the early 2024(till 2024 April),accounting for 40%of the total.These studies cover a variety of scientific subjects including the basic properties of black holes and neutron stars,the outburst of accreting black hole and neutron star X-ray binaries,thermal nuclear burst probes,isolated pulsars,quasi periodical oscillations,cyclotron resonant scattering features,fast radio bursts and gamma-ray bursts,etc.This paper introduces the overall progress with focus on some potential breakthroughs.

Screener3D:a gaseous time projection chamber for ultra-low radioactive material screening

In experiments searching for rare signals,background events from the detector itself are some of the major factors limiting search sensitivity.Screening for ultra-low radioactive detector materials is becoming ever more essential.We propose to develop a gaseous time projection chamber(TPC)with a Micromegas readout for radio screening.The TPC records three-dimensional trajectories of charged particles emitted from a flat sample placed in the active volume of the detector.The detector can distinguish the origin of an event and identify the particle types with information from trajectories,which significantly increases the screening sensitivity.For a particles from the sample surface,we observe that our proposed detector can reach a sensitivity higher than 100 l Bq m-2 within two days.

Radio Luminosity,Black Hole Mass and Eddington Ratio for Quasars from the Sloan Digital Sky Survey

We investigate the MBH-σ＊ relation for radio-loud quasars with redshifl z 〈 0.83 in Data Release 3 of the Sloan Digital Sky Survey （SDSS）. The sample consists of 3772 quasars with better models of the H/4 and [O Ⅲ] lines and available radio luminosity, including 306 radio-loud quasars, 3466 radio-quiet quasars with measured radio luminosity or upper-limit of radio luminosity （181 radio-quiet quasars with measured radio luminosity）. The virial supermassive black hole mass （MBH） is calculated from the broad Hβline, and the host stellar velocity dispersion （σ＊） is traced by the core [O Ⅲ] gaseous velocity dispersion. The radio luminosity and radio loudness are derived from the FIRST catalog. Our results are as follows： （1） For radio-quiet quasars, we confirm that there is no obvious deviation from the MBH-σ＊ relation defined for inactive galaxies when the uncertainties in ~IBH and the luminosity bias are concerned. （2） We find that the radio-loud quasars deviate more from the MBH-σ＊ relation than do the radio-quiet quasars. This deviation is only partly due to a possible cosmological evolution of the MBH-σ＊ relation and the luminosity bias. （3） The radio luminosity is proportional to MBH1.28＋0.23-0.16（LBol/LEdd） ^1.29＋0.31-0.24 for radio-quiet quasars and to -MBH3.10＋0.60-0.70（LBol/LEdd）^4.18＋1.40-1.10 - for radio-loud quasars. The weaker dependence of the radio luminosity on the mass and the Eddington ratio for radio-loud quasars shows that other physical effects would account for their radio luminosities, such as the spin of the black hole.

X-Ray Properties of PSR J1811-1925 by Nu STAR

We analyzed the spectral properties and pulse profile of PSR J1811-1925,a pulsar located in the center of composite supernova remnant(SNR)G11.2-0.3,by using high timing resolution archival data from the Nuclear Spectroscopic Telescope Array Mission(NuSTAR).Analysis of archival Chandra data over different regions rules out the SNR shell as the site of the hard X-ray emission while spectral analysis indicates that the NuSTAR photons originate in the pulsar and its nebula.The pulse profile exhibits a broad single peak up to 35 keV.The jointed spectrum by combining NuSTAR and Chandra can be well fitted by a power-law model with a photon index ofΓ=1.58±0.04.The integrated flux of jointed spectrum over 1-10 keV is 3.36×10^(-12)erg cm^(-2)s^(-1).The spectrum of pulsar having photon indexΓ=1.33±0.06 and a 1-10 keV flux of 0.91×10^(-12)erg cm^(-2)s^(-1).We also performed the phase-resolved spectral analysis by splitting the whole pulse-on phase into five phase bins.The photon indices of the bins are all around 1.4,indicating that the photon index does not evolve with the phase.

Féeton(B-L gauge boson)dark matter for the 511-keV gamma-ray excess and the prediction of low-energy neutrino flux

The féeton is the gauge boson of the U(1)_(B−L) gauge theory.If the gauge coupling constant is extremely small,the féeton becomes a candidate for dark matter.We show that its decay to a pair of an electron and a positron explains the observed Galactic 511-keV gamma-ray excess in a consistent manner.This féeton dark matter decays mainly into pairs neutrino and anti-neutrino.Future low-energy experiments with improved directional capability will enable capturing these neutrino signals.The seesaw-motivated parameter space predicts a relatively short féeton lifetime that is comparable to the current cosmological constraint.

Waveform simulation in PandaX-4T

Signal reconstruction through software processing is a crucial component of the background and signal models in the PandaX-4T experiment,which is a multi-tonne dark matter direct search experiment.The accuracy of signal reconstruction is influenced by various detector artifacts,including noise,dark count of photomultiplier,photoionization of impurities in the detector,and other relevant considerations.In this study,we presented a detailed description of a semi-data-driven approach designed to simulate a signal waveform.This work provides a reliable model for the efficiency and bias of the signal reconstruction in the data analysis of PandaX-4T.By comparing critical variables that relate to the temporal shape and hit pattern of the signals,we found good agreement between the simulation and data.

X-ray Spectroscopy of Dips of Cir X-1

We present X-ray spectral analyses of the low-mass X-ray binary Cir X-1 during X-ray dips, using the Rossi X-ray Timing Explorer （RXTE） data. Each dip was divided into several segments, and the spectrum of each segment was fitted with a three-component blackbody model, in which the first two components are affected by partial covering and the third one is unaffected. A Gaussian emission line is also included in the spectral model to represent the Fe Kα line at - 6.4 keV. The fitted temperatures of the two partially covered components are about 2 keV and 1 keV, while the uncovered component has a temperature of -0.5-0.6 keV. The equivalent blackbody emission radius of the hottest component is the smallest and that of the coolest component is the largest. During the dips the fluxes of the two hot components are linearly correlated, while that of the third component does not show any significant variation. The Fe line flux remains constant, within the errors, during the short dips. However, during the long dips the line flux varies significantly and is positively correlated with the fluxes of the two hot components. These results suggest; （1） that the temperature of the X-ray emitting region decreases with radius, （2） that the Fe Kα line emitting region is close to the hot continuum emitting region, and （3） that the size of the Fe line emitting region is larger than that of the obscuring matter causing the short dips but smaller than the region of that causing the long dips.

The YSZ,Planck - YSZ,XMM scaling relation and its difference between cool-core and non-cool-core clusters

We construct a sample of 70 clusters using data from XMM-Newton and Planck to investigate the YSZ,Planck-YSZ,XMM scaling relation and the cool-core influences on this relation.YSZ,XMM is calculated by accurately de-projected temperature and electron number density profiles derived from XMMNewton.YSZ,Planckis the latest Planck data restricted to our precise X-ray cluster size θ500.To study the cool-core influences on the YSZ,Planck-YSZ,XMM scaling relation,we apply two criteria,namely the limits of central cooling time and classic mass deposition rate,to distinguish cool-core clusters(CCCs) from non-cool-core clusters(NCCCs).We also use YSZ,Planckfrom other papers,which are derived from different methods,to confirm our results.The intercept and slope of the YSZ,Planck-YSZ,XMM scaling relation are A =-0.86 ± 0.30 and B = 0.83 ± 0.06 respectively.The intrinsic scatter is σins= 0.14 ± 0.03.The ratio of YSZ,Planck/YSZ,XMM is 1.03 ± 0.05,which is in excellent statistical agreement with unity.Discrepancies in the YSZ,Planck-YSZ,XMM scaling relation between CCCs and NCCCs are found in the observation.They are independent of the cool-core classification criteria and YSZ,Planckcalculation methods,although the discrepancies are more significant under the classification criteria of classic mass deposition rate.The intrinsic scatter of CCCs(0.04) is quite small compared to that of NCCCs(0.27).The ratio of YSZ,Planck/YSZ,XMM for CCCs is 0.89 ± 0.05,suggesting that CCCs’ YSZ,XMM may overestimate the Sunyaev-Zel’dovich(SZ)signal.By contrast,the ratio of YSZ,Planck/YSZ,XMM for NCCCs is 1.14 ± 0.12,which indicates that NCCCs’ YSZ,XMM may underestimate the SZ signal.

Quasar SDSS J142507.32+323137.4: dual AGNs?

We analyze the optical spectrum of type 1 QSO SDSS J1425＋3231. This object is interesting since its narrow emission lines, such as [O Ⅲ]λλ4959, 5007, are double-peaked, and the line structure can be modeled well by three Gaussian components： two components for the two peaks （we refer to the peaks at low/high redshift as ＂the blue/red component＂） and another one for the line wing which has the same line center as that of the blue component, but is- 3 times broader. The separation between the blue and red components is -500km s-1 with the blue component being -2 times broader than the red one. The Hβ emission can be separated into four components： two for the double-peaked narrow line and two for the broad line which comes from the broad line regions. The black hole mass estimated from the broad Hβ emission line using the typical reverberation mapping relation is 0.85 × 108 M⊙, which is consistent with that derived from parameters of [O Ⅲ]λ 5007 of the blue component. We suggest that this QSO might be a dual AGN system; the broad Hβ emission line is mainly contributed by the primary black hole （traced by the blue component） while the broad Hβ component of the secondary black hole （traced by the red component） is hard to be separated out considering a resolution of - 2 000 for SDSS spectra or it may be totally obscured by the dusty torus.

Fe Kα line profile in AGNs: average shape and redshift dependence

We collect a sample of 381 （271 type Ⅰ） active galactic nuclei （AGNs） with XMM-Newton observations for an analysis of the dependence of Fe Kα profiles on redshifts to test the potential cosmological evolution of spins of supermassive black holes （SMBHs）. The sample spans a redshift range of z = 0.0008 - 4.76, which allows us to rebin the sample into 7 redshift groups. Phenomenological analysis of the Fe profile suggested that the line width （δ） of the narrow or broad Fe line does not show significant changes in redshift range z 〈 0.3. Using a physical model, we significantly detect a narrow Fe Kα line at 6.4 keV with an average equivalent width （EW） = 160 eV except for the two largest redshift bins. The EW of the Fe line does not show significant changes. We also find a relativistic broad line in three redshift bins （z 〈 0.116, 0.056 〈 z 〈 0.12 and 0.12 〈 z 〈 0.3）with an average EW = 522eV.

Detecting radio afterglows of gamma-ray bursts with FAST

Using the generic hydrodynamic model of gamma-ray burst （GRB） after- glows, we calculate the radio afterglow light curves of low luminosity, high luminosity, failed and standard GRBs in different observational bands of FAST＇s energy window. The GRBs are assumed to be located at different distances from us. Our results rank the detectability of GRBs in descending order as high luminosity, standard, failed and low luminosity GRBs. We predict that almost all types of radio afterglows except those of low luminosity GRBs could be observed by a large radio telescope as long as the domains of time and frequency are appropriate. It is important to note that FAST can detect relatively weak radio afterglows at a higher frequency of 2.5 GHz for very high redshift up to z = 15 or even more. Radio afterglows of low luminosity GRBs can only be detected after the completion of the second phase of FAST. FAST is expected to significantly expand the sample of GRB radio afterglows in the near future.

Discrimination of background events in the PolarLight X-ray polarimeter

PolarLight is a space-borne X-ray polarimeter that measures the X-ray polarization via electron tracking in an ionization chamber.It is a collimated instrument and thus suffers from the background on the whole detector plane.The majority of background events are induced by high energy charged particles and show ionization morphologies distinct from those produced by X-rays of interest.Comparing on-source and off-source observations,we find that the two datasets display different distributions on image properties.The boundaries between the source and background distributions are obtained and can be used for background discrimination.Such a means can remove over 70%of the background events measured with PolarLight.This approaches the theoretical upper limit of the background fraction that is removable and justifies its effectiveness.For observations with the Crab nebula,the background contamination decreases from 25%to 8%after discrimination,indicative of a polarimetric sensitivity of around 0.2 Crab for PolarLight.This work also provides insights into future X-ray polarimetric telescopes.

Disk-Corona Model in Active Galactic Nuclei: an Observational Test

We compiled a sample of 98 radio-quiet active galactic nuclei observed by ASCA, Chandra, XMM-Newton, INTEGRAL and Swift with the aim of testing the formation of hot corona and the magnetic shear stress operating in a disk-corona system. We found a strong correlation between the hard X-ray luminosity, bolometric luminosity LBol and Eddington luminosity LEdd, in the sense that the fraction f of hard X-ray to the bolometric luminosity is inversely proportional to the Eddington ratio. This correlation favors the shear stress tensor being of the form of trФ∝ Pgas, with which the disk-corona structure is stable.

SDSS J143030.22-001115.1: A Misclassified Narrow-line Seyfert 1 Galaxy with Flat X-ray Spectrum

We used multi-component profiles to model the HE and [O Ⅲ]λλ4959,5007 lines of SDSS J143030.22-001115.1, a narrow-line Seyfert 1 galaxy （NLS1） in a sample of 150 NLS1 candidates selected from the Sloan Digital Sky Survey （SDSS）, Early Data Release （EDR）. After subtracting the HE contribution from narrow line regions （NLRs）, we found that its full width half maximum （FWHM） of broad H/3 line is nearly 2900km s^-1, significantly larger than the customarily adopted criterion of 2000 km s^-1. With its weak Fe II multiples, we believe that SDSS J143030.22-001115.1 should not be classified as a genuine NLS1. When we calculate the virial black hole masses of NLSls, we should use the Hβ linewidth after subtracting the NLR component.

Search for charm-quark production via dimuons in neutrino telescopes

Dimuon events induced by charm-quark productions from neutrino deep inelastic scattering(DIS) processes have been studied in traditional DIS experiments for decades.The recent progress in neutrino telescopes makes it possible to search for such dimuon events at energies far beyond the laboratory scale.In this study,we construct a simulation framework to calculate yields and distributions of dimuon signals in an IceCube-like km3scale neutrino telescope.Owing to the experimental limitation in the resolution of double-track lateral distance,only dimuons produced outside the detector volume are considered.Detailed information about simulation results for a10-year exposure is presented.As an earlier paper [Physical Review D 105,093005(2022)] and ours report on a similar situation,we use that paper as a baseline to conduct comparisons.We then estimate the impacts of different calculation methods of muon energy losses.Finally,we study the experimental potential of dimuon searches under the hypothesis of single-muon background only.Our results based on a simplified double-track reconstruction indicate a moderate sensitivity,especially with the ORCA configuration.Further developments on both the reconstruction algorithm and possible detector designs are thus required and are under investigation.

Topological Equivalence Theorem and Double-Copy for Chern-Simons Scattering Amplitudes

We study the mechanism of topological mass generation for 3-dimensional Chern-Simons gauge theories and propose a brand-new topological equivalence theorem to connect scattering amplitudes of the physical gauge boson states to that of the transverse states under high-energy expansion.

A gaseous time projection chamber with Micromegas readout for low-radioactive material screening

Purpose Low-radioactive material screening is becoming essential for rare event search experiments,such as neutrinoless double beta decay and dark matter searches in underground laboratories.A gaseous time projection chamber(TPC)can be used for such purposes with large active areas and high efficiency.Methods A gaseous TPC with a Micromegas readout plane of approximately 20×20 cm^(2)is successfully constructed for surface alpha contamination measurements.Results We have characterized the energy resolution,gain stability,and tracking capability with calibration sources.Conclusion With the unique track-related background suppression cuts of the gaseous TPC,we have established that the alpha background rate of the TPC is(0.13±0.03)×10^(−6)Bq/cm^(2),comparable to the leading commercial solutions.

A comparative lattice analysis of SU(2)dark glueballs

We study the mass and scattering cross section of SU(2)glueballs as dark matter candidates using lattice simulations.We employ both naive and improved SU(2)gauge actions in 3+1 dimensions with severalβvalues,and we adopt both the traditional Monte Carlo method and flow-based model based on machine learning techniques to generate lattice configurations.The mass of a dark scalar glueball with J^(PC)=0^(++)and the Nambu-Bethe-Salpeter wave function are calculated.Using a coupling constant ofβ=2.2 as an illustration,we compare the dark glueball mass calculated from the configurations generated from the two methods.While consistent results can be achieved,the two methods demonstrate distinct advantages.Using the Runge-Kutta method,we extract the glueball interaction potential and two-body scattering cross section.From the observational constraints,we obtain the lower bound of the mass of scalar glueballs as candidates of dark matter.