All Results

Insight-HXMT observations of the first binary neutron star merger GW170817

TiPei Li; ShaoLin Xiong; ShuangNan Zhang; FangJun Lu; LiMing Song; XueLei Cao; Zhi Chang; Gang Chen; Li Chen; TianXiang Chen; Yong Chen; YiBao Chen; YuPeng Chen; Wei Cui; WeiWei Cui; JingKang Deng; YongWei Dong; YuanYuan Du; MinXue Fu; GuanHua GaoSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

Finding the electromagnetic (EM) counterpart of binary compact star merger, especially the binary neutron star (BNS) merger, is critically important for gravitational wave (GW) astronomy, osmology and fundamental physics. On Aug. 17, 2017, Advanced LIGO and Fermi/GBM independently triggered the first BNS merger, GW170817, and its high energy EM counterpart, GRB 170817A, respectively, resulting in a global observation campaign covering gamma-ray, X-ray, UV, optical, IR, radio as well as neutrinos. The High Energy X-ray telescope (HE) onboard Insight-HXMT (Hard X-ray Modulation Telescope) is the unique high-energy gamma-ray telescope that monitored the entire GW localization area and especially the optical counterpart (SSS17a/AT2017gfo) with very large collection area (~1000 cm2) and microsecond time resolution in 0.2-5 MeV. In addition, Insight-HXMT quickly implemented a Target of Opportunity (ToO) observation to scan the GW localization area for potential X-ray emission from the GW source. Although Insight-HXMT did not detect any significant high energy (0.2-5 MeV) radiation from GW170817, its observation helped to confirm the nexpected weak and soft nature of GRB 170817A. Meanwhile, Insight-HXMT/HE provides one of the most stringent constraints (~10-7 to 10-6 erg/cm2/s) for both GRB170817A and any other possible precursor or extended emissions in 0.2-5 MeV, which help us to better understand the properties of EM radiation from this BNS merger. Therefore the observation of Insight-HXMT constitutes an important chapter in the full context of multi-wavelength and multi-messenger observation of this historical GW event. |

Status of Natural Supersymmetry from the GmSUGRA in Light of the current LHC Run-2 and LUX data

Waqas Ahmed; Xiao-Jun Bi; Tianjun Li; Jia Shu Niu; Shabbar Raza; Qian-Fei Xiang; Peng-Fei YinSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

We study natural supersymmetry in the Generalized Minimal Supergravity (GmSUGRA).For the parameter space with low energy electroweak fine-tuning measures less than 50, we are left with only the Z-pole, Higgs-pole and Higgsino LSP scenarios for dark matter (DM). We perform the focused scans for such parameter space and find that it satisfies various phenomenological constraints and is compatible with the current direct detection bound on neutralino DM reported by the LUX experiment. Such parameter space also has solutions with correct DM relic density besides the solutions with DM relic density smaller or larger than 5 WMAP9 bounds. We present five benchmark points as examples. In these benchmark points, gluino and the first two generations of squarks are heavier than 2 TeV, stop ˜t1,2 are in the mass range [1, 2] TeV, while sleptons are lighter than 1 TeV. Some part of the parameter space can explain the muon anomalous magnetic moment within 3 as well. We also perform the collider study of such solutions by implementing and comparing with relevant studies done by the ATLAS and CMS Collaborations. We find that the points with Higgsino dominant ˜ 02/ ˜ ±1 mass upto 300 GeV are excluded in Z-pole scenario while for Higgs-pole scenario, the points with ˜ 02 mass up to 460 GeV are excluded. We also notice that the Higgsino LSP points in our present scans are beyond the reach of present LHC searches. Next, we show that for both the Z-pole and Higgs-pole scenarios, the points with electroweak fine-tuning measure around 20 do still survive. |

Six-quark structure of d#3;(2380) in chiral constituent quark model

Qi-Fang L╱,; Fei Huang,; Yu-Bing Dong,; Peng-Nian Shen,; Zong-Ye ZhangSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

On the charge distribution of d#3;(2380)

Yubing Dong,; Fei Huang, Pengnian Shen,; Zongye ZhangSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

Decay width of d (2380) ! NN process in a chiral constituent quark model

Yubing Dong; Fei Huang; Pengnian Shen; Zongye ZhangSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

The width of three-body single-pion decay process d∗ → NNπ0,± is calculated by using the d∗ wave function obtained from our chiral SU(3) constituent quark model calculation. The eﬀect of the dynamical structure on the width of d∗ is taken into account in both the single ∆∆ channel and cou-pled ∆∆+CC two-channel approximations. Our numerical result shows that in the coupled-channel approximation, namely, the hidden-color conﬁguration being considered, the obtained partial decay width of d∗ → NNπ is about several hundred KeV, while in the single ∆∆ channel it is just about 2 ∼ 3 MeV. We, therefore, conclude that the partial width in the single-pion decay process of d∗ is much smaller than the widths in its double-pion decay processes. Our prediction may provide a criterion for judging diﬀerent interpretations of the d∗ structure, as diﬀerent pictures for the d∗ may result quite diﬀerent partial decay width. |

How Large is the Contribution of Excited Mesons in Coupled-Channel Effects?

Yu Lu; Muhammad Naeem Anwar; Bing-Song ZouSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

We study the excited B mesons' contributions to the coupled-channel e ects under the framework of the 3P0 model for the bottomonium. Contrary to what has been widely accepted, the contributions of P wave B mesons are generally the largest, and to some extent, this result is independent of the potential parameters. We also push the calculation beyond B(1P) and carefully analyze the contributions of B(2S). A form factor is a key ingredient to suppress the contributions of B(2S) for low lying bottomonia. However, this suppression mechanism is not e cient for highly excited bottomonia, such as (5S) and (6S). We give explanations why this di culty happens to the 3P0 model and suggest analyzing the ux-tube breaking model for the full calculation of coupled-channel e ects. |

Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

A detailed theoretical derivation of the cross sections of e+e− → e+e− and e+e− → µ+µ− around the J/ψ resonance is reported. The resonance and interference parts of the cross sections, related to J/ψ resonance parameters, are calculated. Higher-order corrections for vacuum polarization and initial-state radiation are consid-ered. An arbitrary upper limit of radiative correction integration is involved. Full and simpliﬁed versions of analytic formulae are given with precision at the level of 0.1% and 0.2%, respectively. Moreover, the results obtained in the paper can be applied to the case of the ψ(3686) resonance. |

Motion of photons in a background of gravitational wave

Zhe Chang; Chao-Guang Huang; Zhi-Chao ZhaoSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

The photon motion in a Michelson interferometer is re-analyzed in both geometrical optics and wave optics. The classical paths of the photons in the background of gravitational wave are derived from Fermat principle, which is the same as the null geodesics in general relativity. The deformed Maxwell equations and the wave equations of electric elds in the background of gravitational wave are presented in at-space approximation. Both methods show that the response of an interferometer depends on the frequency of a gravitational wave, however it is almost independent of the frequency of the mirror's vibrations. It implies that the vibrating mirror cannot mimic a gravitational wave very well. |