Invisible Higgs Decay at the LHeC

The possibility that the 125 GeV Higgs boson may decay into invisible non-standard-model (non-SM) particles is theoretically and phenomenologically intriguing. In this letter we investigate the sensitivity of the Large Hadron Electron Collider (LHeC) to an invisibly decaying Higgs, in its proposed high luminosity running mode. We focus on the neutral current Higgs production channel which offers more kinematical handles than its charged current counterpart. The signal contains one electron, one jet and large missing energy. With a cut-based parton level analysis, we estimate that if the $hZZ$ coupling is at its standard model (SM) value, then assuming an integrated luminosity of 1\,\mbox{ab}^{-1} the LHeC with the proposed 60 GeV electron beam (with $-0.9$ polarization) and 7 TeV proton beam is capable of probing $\mathrm{Br}(h\rightarrow E\!\!\!\!/_T)=6\%$ at $2\sigma$ level. Good lepton veto performance (especially hadronic $\tau$ veto) in the forward region is crucial to the suppression of the dominant $Wje$ background. We also explicitly point out the important role that may be played by the LHeC in probing a wide class of exotic Higgs decay processes and emphasize the general function of lepton-hadron colliders in precision study of new resonances after their discovery in hadron-hadron collisions.Comment: 6 pages, 3 figures. Description of the backgrounds, analysis and results is simplified. Results unchanged with respect to v2. References update

Exotic Higgs Decay h→ϕϕ→4bh\rightarrow\phi\phi\rightarrow 4b at the LHeC

We study the exotic decay of the 125 GeV Higgs boson ($h$) into a pair of light spin-0 particles ($\phi$) which subsequently decays and results in a $4b$ final state. This decay mode is well motivated in the Next to Minimal Supersymmetric Standard Model (NMSSM) and extended Higgs sector models. Instead of searching at the Large Hadron Collider (LHC) and the High Luminosity Large Hadron Collider (HL-LHC) which are beset by large Standard Model (SM) backgrounds, we investigate this decay channel at the much cleaner Large Hadron Electron Collider (LHeC). With some simple selection cuts this channel becomes nearly free of background at this $ep$ machine, in stark contrast with the situation at the (HL-)LHC. With a parton level analysis we show that for the $\phi$ mass range $[20,60]GeV$, with $100\,fb^{-1}$ luminosity the LHeC is generally capable of constraining $C_{4b}^2\equiv\kappa_{V}^2\times\text{Br}(h\rightarrow\phi\phi)\times\text{Br}^2(\phi\rightarrow b\bar{b})$ ($\kappa_{V}$ denotes the $hVV(V=W,Z)$ coupling strength relative to the SM value) to a few percent level ($95\%$ CLs). With $1\,ab^{-1}$ luminosity $C_{4b}^2$ at a few per mille level can be probed. These sensitivities are much better than the HL-LHC performance and demonstrate the important role expected to be played by the LHeC in probing exotic Higgs decay processes, in addition to the already proposed invisible Higgs decay channel.Comment: 10 pages, 5 figures. Version accepted by EPJC. Tables and figures updated after correcting a mistake in signal event generation. Results essentially unchange

Entanglement Entropy and Quantum Phase Transition in the O(N)O(N) σ\sigma-model

We investigate how entanglement entropy behaves in a system with a quantum phase transition. We study the $\sigma$-model which has an $O(N)$ symmetry when the mass squared parameter $\mu^2$ is positive, and when $\mu^2$ is negative, this symmetry is broken spontaneously. The area law and the leading divergence of entanglement entropy are preserved in both the symmetric and the broken phases. In 3+1 dimensions, the spontaneous symmetry breaking changes the subleading divergence from a log to log squared, while in 2+1 dimensions the subleading divergent structure is unchanged. At the leading order of the coupling constant expansion, the entanglement entropy reaches its local maximum with a cusp at the quantum phase transition point $\mu^2=0$ and decreases while $|\mu^2|$ is increased. We also find novel scaling behavior of the entanglement entropy near the transition point.Comment: 32 pp., 6 figures. v2. scaling behavior revised, 3 references added, submitted to JHE

Structural and Thermodynamic Factors of Suppressed Interdiffusion Kinetics in Multi-component High-entropy Materials

We report multi-component high-entropy materials as extraordinarily robust diffusion barriers and clarify the highly suppressed interdiffusion kinetics in the multi-component materials from structural and thermodynamic perspectives. The failures of six alloy barriers with different numbers of elements, from unitary Ti to senary TiTaCrZrAlRu, against the interdiffusion of Cu and Si were characterized, and experimental results indicated that, with more elements incorporated, the failure temperature of the barriers increased from 550 to 900°C. The activation energy of Cu diffusion through the alloy barriers was determined to increase from 110 to 163 kJ/mole. Mechanistic analyses suggest that, structurally, severe lattice distortion strains and a high packing density caused by different atom sizes, and, thermodynamically, a strengthened cohesion provide a total increase of 55 kJ/mole in the activation energy of substitutional Cu diffusion, and are believed to be the dominant factors of suppressed interdiffusion kinetics through the multi-component barrier materials

Miyun 232 MHz survey 1: Fields centered at: alpha:00(h)41(m), delta:41 deg 12 min and alpha: 07(h)00(m),delta:35 deg 00 min

A new meter-wave survey of sky region north of declination +30 deg is carried out with the Miyun 232 MHz Synthesis Radio Telescope (MSRT). The instrument, observation, and method of data reduction are briefly described. A preliminary catalog, first of a series, for two 8 deg. x 8 deg. regions centered respectively at 35 deg. is presented. On the average 4 - 5 sources per square degree are recorded with position accuracy of 5 sec. / S(Jy). BGPW scale is adopted for the flux density calibration. The accuracy of flux determination is limited by background fluctuation which is about 30 mJy. The catalog is complete for sources with flux larger than 0.25 Jy. The total number of sources listed in the paper amounts to 687. Several extended sources, sources with convex spectra, and one GPS source were found. Spectra of sources with flux larger than 0.5 Jy were also given