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.

Preparation for CSST:Star-galaxy Classification using a Rotationally Invariant Supervised Machine Learning Method

Most existing star-galaxy classifiers depend on the reduced information from catalogs,necessitating careful data processing and feature extraction.In this study,we employ a supervised machine learning method(GoogLeNet)to automatically classify stars and galaxies in the COSMOS field.Unlike traditional machine learning methods,we introduce several preprocessing techniques,including noise reduction and the unwrapping of denoised images in polar coordinates,applied to our carefully selected samples of stars and galaxies.By dividing the selected samples into training and validation sets in an 8:2 ratio,we evaluate the performance of the GoogLeNet model in distinguishing between stars and galaxies.The results indicate that the GoogLeNet model is highly effective,achieving accuracies of 99.6% and 99.9% for stars and galaxies,respectively.Furthermore,by comparing the results with and without preprocessing,we find that preprocessing can significantly improve classification accuracy(by approximately 2.0% to 6.0%)when the images are rotated.In preparation for the future launch of the China Space Station Telescope(CSST),we also evaluate the performance of the GoogLeNet model on the CSST simulation data.These results demonstrate a high level of accuracy(approximately 99.8%),indicating that this model can be effectively utilized for future observations with the CSST.

Erratum:A Search for Solar Axions and Anomalous Neutrino Magnetic Moment with the Complete PandaX-Ⅱ Data[CHIN.PHYS.LETT.38(2021)011301]

In our published letter,[1]we have identified a minor error in Figs.2 and 3.Instead,we have 2111 events in these two plots with 646,249,382,and 834 events in Run 9(20.0 ton·day),Run 10(19.4 ton·day),Run 11–1(24.2 ton·day),and Run 11–2(37.1 ton·day).The mistake is due to an incorrect application of a small energy non-linearity(known as the BLS non-linearity)in making plots,but has no impact to the final results.Figures 2 and 3 are now updated in this note.

A Search for Solar Axions and Anomalous Neutrino Magnetic Moment with the Complete Panda X-Ⅱ Data

We report a search for new physics signals using the low energy electron recoil events in the complete data set from PandaX-Ⅱ,in light of the recent event excess reported by XENON1 T.The data correspond to a total exposure of 100.7 ton·day with liquid xenon.With robust estimates of the dominant background spectra,we perform sensitive searches on solar axions and neutrinos with enhanced magnetic moment.It is found that the axionelectron coupling gAe<4.6×10^(-12) for an axion mass less than 0.1 keV/c^(2) and the neutrino magnetic moment μv<4.9×10^(-11)μB at 90%confidence level.The observed excess from XENON1 T is within our experimental constraints.

Constraints on the skewness coefficient of symmetric nuclear matter within the nonlinear relativistic mean field model

Within the nonlinear relativistic mean field(NLRMF) model, we show that both the pressure of symmetric nuclear matter at supra-saturation densities and the maximum mass of neutron stars are sensitive to the skewness coefficient, J_0, of symmetric nuclear matter. Using experimental constraints on the pressure of symmetric nuclear matter at supra-saturation densities from flow data in heavy-ion collisions and the astrophysical observation of a large mass neutron star PSR J0348+0432, with the former favoring a smaller J_0 while the latter favors a larger J_0, we extract a constraint of -494 MeV≤J_0≤-10 MeV based on the NL-RMF model. This constraint is compared with the results obtained in other analyses.

How tightly is the nuclear symmetry energy constrained by a unitary Fermi gas?

We examine critically how tightly the density dependence of nuclear symmetry energy E_(sym)(q) is constrained by the universal equation of state of the unitary Fermi gas EUG(q) considering currently known uncertainties of higher order parameters describing the density dependence of the equation of state of isospin asymmetric nuclear matter. We found that E_(UG)(q) does provide a useful lower boundary for the E_(sym)(q). However, it doesnot tightly constrain the correlation between the magnitude E_(sym)(q_0) and slope L unless the curvature K_(sym)of the symmetry energy at saturation density q_0 is more precisely known. The large uncertainty in the skewness parameters affects the E_(sym)(q_0) versus L correlation by the same almost as significantly as the uncertainty in K_(sym).

On proportional scintillation in very large liquid xenon detectors

The charge readout of a liquid xenon(LXe)detector via proportional scintillation in the liquid phase was first realized by the Waseda group 40 years ago,but the technical challenges involved were overwhelming.Although the tests were successful,this method was finally discarded and eventually nearly forgotten.Currently,this approach is not considered for large LXe dark matter detectors.Instead,the dual-phase technology was selected despite many limitations and challenges.In two independent studies,two groups from Columbia University and Shanghai Jiao Tong University reevaluated proportional scintillation in the liquid phase.Both studies established the merits for very large LXe detectors,but the Columbia group also encountered apparent limitations,namely the shadowing of the light by the anode wires,and a dependence of the pulse shape on the drift path of the electrons in the anode region.The differences between the two studies,however,are not intrinsic to the technique,but a direct consequence of the chosen geometry.Taking the geometrical differences into account,the results match without ambiguity.They also agree with the original results from the Waseda group.

Isospin dependence of nucleon effective masses in neutron-rich matter

In this talk,we first briefly review the isospin dependence of the total nucleon effective mass M Jinferred from analyzing nucleon-nucleus scattering data within an isospin-dependent non-relativistic optical potential model,and the isospin dependence of the nucleon E-mass M;E J obtained from applying the Migdal–Luttinger theorem to a phenomenological single-nucleon momentum distribution in nuclei constrained by recent electron-nucleus scatteringexperiments.Combining information about the isospin dependence of both the nucleon total effective mass and E-mass,we then infer the isospin dependence of nucleon k-mass using the well-known relation M_J~*=M_ J^(*1E).Implications of the results on the nucleon mean free path in neutron-rich matter are discussed.

Size distribution of galaxies in SDSS DR7:weak dependence on halo environment

Using a sample of galaxies selected from the Sloan Digital Sky Survey Data Release 7(SDSS DR7) and a catalog of bulge-disk decompositions, we study how the size distribution of galaxies depends on the intrinsic properties of galaxies, such as concentration, morphology, specific star formation rate(sSFR),and bulge fraction, and on the large-scale environments in the context of central/satellite decomposition,halo environment, the cosmic web: cluster, filament, sheet and void, as well as galaxy number density. We find that there is a strong dependence of the luminosity-or mass-size relation on the galaxy concentration, morphology, s SFR and bulge fraction. Compared with late-type(spiral) galaxies, there is a clear trend of smaller sizes and steeper slope for early-type(elliptical) galaxies. Similarly, galaxies with a high bulge fraction have smaller sizes and steeper slopes than those with a low bulge fraction. Fitting formulae of the average luminosity-and mass-size relations are provided for galaxies with these different intrinsic properties. Examining galaxies in terms of their large scale environments, we find that the masssize relation has some weak dependence on the halo mass and central/satellite segregation for galaxies within mass range 9.0 ≤ log M*≤ 10.5, where satellites or galaxies in more massive halos have slightly smaller sizes than their counterparts, while the cosmic web and local number density dependence of the mass-size relation is almost negligible.

Toward accurate measurement of property-dependent galaxy clustering I.Comparison of the Vmax method and the“shuffled”method

Galaxy clustering provides insightful clues to our understanding of galaxy formation and evolution,as well as the universe.The redshift assignment for the random sample is one of the key steps to accurately measure galaxy clustering.In this paper,by virtue of the mock galaxy catalogs,we investigate the effect of two redshift assignment methods on the measurement of galaxy two-point correlation functions(hereafter 2 PCFs),the Vmax method and the"shuffled"method.We have found that the shuffled method significantly underestimates both of the projected 2 PCFs and the two-dimensional 2 PCFs in redshift space,while the Vmax method does not show any notable bias on the 2 PCFs for volume-limited samples.For fluxlimited samples,the bias produced by the Vmax method is less than half of the shuffled method on large scales.Therefore,we strongly recommend the Vmax method to assign redshifts to random samples in the future galaxy clustering analysis.

The bar and spiral arms in the Milky Way: structure and kinematics

The Milky Way is a spiral galaxy with the Schechter characteristic luminosity L*,thus an important anchor point of the Hubble sequence of all spiral galaxies.Yet the true appearance of the Milky Way has remained elusive for centuries.We review the current best understanding of the structure and kinematics of our home galaxy,and present an updated scientifically accurate visualization of the Milky Way structure with almost all components of the spiral arms,along with the COBE image in the solar perspective.The Milky Way contains a strong bar,four major spiral arms,and an additional arm segment(the Local arm)that may be longer than previously thought.The Galactic boxy bulge that we observe is mostly the peanut-shaped central bar viewed nearly end-on with a bar angle of^25°-30°from the SunGalactic center line.The bar transitions smoothly from a central peanut-shaped structure to an extended thin part that ends around R^5 kpc.The Galactic bulge/bar contains^30%-40%of the total stellar mass in the Galaxy.Dynamical modelling of both the stellar and gas kinematics yields a bar pattern rotation speed of^35-40 km s-1 kpc-1,corresponding to a bar rotation period of^160-180 Myr.From a galaxy formation point of view,our Milky Way is probably a pure-disk galaxy with little room for a significant merger-made,"classical"spheroidal bulge,and we give a number of reasons why this is the case.

The intrinsic SFRF and sSFRF of galaxies:comparing SDSS observation with IllustrisTNG simulation

The star formation rate function(SFRF) and specific star formation rate function(s SFRF) from observations are impacted by the Eddington bias, due to uncertainties in the estimated star formation rate(SFR). We develop a novel method to correct the Eddington bias and obtain the intrinsic SFRF and sSFRF from the Sloan Digital Sky Survey(SDSS) Data Release 7. The intrinsic SFRF is in good agreement with measurements from previous data in the literature that relied on UV SFRs but its high star-forming end is slightly lower than the corresponding IR and radio tracers. We demonstrate that the intrinsic sSFRF from SDSS has a bimodal form with one peak found at sSFR ~10-9.7 yr^-1 representing the star-forming objects while the other peak is found at sSFR ~10-12 yr^-1 representing the quenched population. Furthermore, we compare our observations with the predictions from the Illustris TNG and Illustris simulations and affirm that the "TNG" model performs much better than its predecessor. However,we show that the simulated SFRF and CSFRD of TNG simulations are highly dependent on resolution,reflecting the limitations of the model and today’s state-of-the-art simulations. We demonstrate that the bimodal, two peaked s SFRF implied by the SDSS observations does not appear in TNG regardless of the adopted box-size or resolution. This tension reflects the need for inclusion of an additional efficient quenching mechanism in the TNG model.

Expansion series of the pairwise velocity generating function and its implications on redshift space distortion modeling

The pairwise velocity generating function G has a deep connection with both the pairwise velocity probability distribution function and modeling of redshift space distortion(RSD).Its implementation into RSD modeling is often faciliated by expansion into a series of pairwise velocity moments(v^(n)_(12))-Motivated by the logrithmic transformation of the cosmic density field,we investigate an alternative expansion into series of pairwise velocity cumulants(v^(n)_(12))c.We numerically evaluate the convergence rate of the two expansions,with three 30723 particle simulations of the CosmicGrowth N-body simulation series.(1)We find that the cumulant expansion performs significantly better,for all the halo samples and redshifts investigated.(2)For modeling RSD at k||<O.1h Mpc^(-1),including only the n=1,2 cumulants is sufficient.(3)But for modeling RSD at k||=0.2h Mpc^(-1),we need and only need the n=1,2,3,4 cumulants.These results provide specific requirements on RSD modeling in terms of m-th order statistics of the large-scale structure.

Weak lensing magnification reconstruction with the modified internal linear combination method

Measuring weak lensing cosmic magnification signal is very challenging due to the overwhelming intrinsic clustering in the observed galaxy distribution.In this paper,we modify the Internal Linear Combination(ILC)method to reconstruct the lensing signal with an extra constraint to suppress the intrinsic clustering.To quantify the performance,we construct a realistic galaxy catalogue for the LSST-like photometric survey,covering 20000 deg^(2) with mean source redshift at z_(s)~1.We find that the reconstruction performance depends on the width of the photo-z bin we choose.Due to the correlation between the lensing signal and the source galaxy distribution,the derived signal has smaller systematic bias but larger statistical uncertainty for a narrower photo-z bin.We conclude that the lensing signal reconstruction with the Modified ILC method is unbiased with a statistical uncertainty <5% for bin width Δz^(P)=0.2.

The Halo Concentration and Mass Relation Traced by Satellite Galaxies

We study the relation between halo concentration and mass(c-M relation) using galaxy catalogs of the Seventh and Eighth Data Releases of the Sloan Digital Sky Survey(SDSS DR7 and DR8). Assuming that the satellite galaxies follow the distribution of dark matter, we derive the halo concentration by fitting the satellite radial profile with a Nararro Frank and White(NFW) format. The derived c-M relation covers a wide halo mass range from10^(11.6)to 10^(14.1)M_(⊙). We confirm the anti-correlation between the halo mass and concentration as predicted in cosmological simulations. Our results are in good agreement with those derived using galaxy dynamics and gravitational lensing for halos of 10^(11.6)– 10^(12.9)M_(⊙), while they are slightly lower for halos of 10^(12.9)– 10^(14.1)M_(⊙).This is because blue satellite galaxies are less concentrated, especially in the inner regions. Instead of using all satellite galaxies, red satellites could be better tracers of the underlying dark matter distribution in galaxy groups.

Unambiguously Resolving the Potential Neutrino Magnetic Moment Signal at Large Liquid Scintillator Detectors

Non-vanishing electromagnetic properties of neutrinos have been predicted by many theories beyond the Standard Model, and an enhanced neutrino magnetic moment can have profound implications for fundamental physics. The XENON1T experiment recently detected an excess of electron recoil events in the 1–7 keV energy range, which can be compatible with solar neutrino magnetic moment interaction at a most probable value of μ_(v) = 2.1 × 10^(-11)μ_(B).However, tritium backgrounds or solar axion interaction in this energy window are equally plausible causes.Upcoming multi-tonne noble liquid detectors will test these scenarios more in depth, but will continue to face similar ambiguity. We report a unique capability of future large liquid scintillator detectors to help resolve the potential neutrino magnetic moment scenario. With O(100) kton·year exposure of liquid scintillator to solar neutrinos, a sensitivity of μ_(v) < 10^(-11)μ_(B) can be reached at an energy threshold greater than 40 keV, where no tritium or solar axion events but only neutrino magnetic moment signal is still present.

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.

Future Physics Programme of BESⅢ

There has recently been a dramatic renewal of interest in hadron spectroscopy and charm physics. This renaissance has been driven in part by the discovery of a plethora of charmonium-like XYZ states at BESⅢ and B factories, and the observation of an intriguing proton-antiproton threshold enhancement and the possibly related X(1835) meson state at BESⅢ, as well as the threshold measurements of charm mesons and charm baryons. We present a detailed survey of the important topics in tau-charm physics and hadron physics that can be further explored at BESⅢ during the remaining operation period of BEPCⅡ. This survey will help in the optimization of the data-taking plan over the coming years, and provides physics motivation for the possible upgrade of BEPCⅡ to higher luminosity.