Search

We conduct the first-ever Pulsar Polarization Array (PPA) analysis to detect the ultralight Axion-Like Dark Matter (ALDM) using the polarization data of 22 millisecond pulsars from the third data release of Parkes Pulsar Timing Array. As one of the major dark matter candidates, the ultralight ALDM exhibits a pronounced wave nature on astronomical scales and offers a promising solution to small-scale structure issues within local galaxies. While the linearly polarized pulsar light travels through the ALDM galactic halo, its position angle (PA) can be subject to an oscillation induced by the ALDM Chern-Simons coupling with electromagnetic field. The PPA is thus especially suited for detecting the ultralight ALDM by correlating polarization data across the arrayed pulsars. To accomplish this task, we develop an advanced Bayesian analysis framework that allows us to construct pulsar PA residual time series, model noise contributions properly and search for pulsar cross-correlations. We find that for an ALDM density of $\rho_0=0.4\,\textrm{GeV}/\textrm{cm}^3$, the Parkes PPA offers the best global limits on the ALDM Chern-Simons coupling, namely $\lesssim 10^{-13.5}-10^{-12.2}~{\rm GeV}^{-1}$, for the mass range of $10^{-22} - 10^{-21}~{\rm eV}$. The crucial role of pulsar cross-correlation in recognizing the nature of the derived limits is also highlighted., Comment: 6+15 pages, 10 figures, 2 tables, submitted to the journal

The rapid progress in gravitational wave astronomy has provided an opportunity for investigating the presence of long-range scalar forces that exclusively manifest around astrophysical black holes. In this paper, we explore a new possibility in this context, particularly in connection to the hypothesis that astrophysical black holes might be horizonless ultracompact objects (UCOs). In the absence of horizons, UCOs could feature unique interiors with extreme environments. This could help generate non-trivial scalar profiles and significant scalar charges. For demonstration, we consider 2-2-holes in quadratic gravity as a concrete example of UCOs. These objects can be formed by ordinary gases and closely resemble black holes externally. However, they have distinct interiors characterized by high curvatures and substantial redshift. In particular, the gases inside could reach extremely high temperatures or densities, making them an ideal object for investigating the generation of scalar profiles by UCOs. Within a minimal model of the scalar field, we find that this unique environment enables the generation of a substantial scalar charge for astrophysical 2-2-holes, which is challenging for other stellar objects. The predicted scalar charge-to-mass ratio of 2-2-holes remains nearly constant across a wide range of masses, offering different predictions for gravitational wave observations compared to other mechanisms., Comment: 30 pages, 10 figures. v2: typos fixed, matches published version in PRD

High-frequency gravitational waves (HFGWs) carry a wealth of information on the early Universe with a tiny comoving horizon and astronomical objects of small scale but with dense energy. We demonstrate that the nearby planets, such as Earth and Jupiter, can be utilized as a laboratory for detecting the HFGWs. These GWs are then expected to convert to signal photons in the planetary magnetosphere, across the frequency band of astronomical observation. As a proof of concept, we present the first limits from the existing low-Earth-orbit satellite for specific frequency bands and project the sensitivities for the future more-dedicated detections. The first limits from Juno, the latest mission orbiting Jupiter, are also presented. Attributed to the long path of effective GW-photon conversion and the wide angular distribution of signal flux, we find that these limits are highly encouraging, for a broad frequency range including a large portion unexplored before., Comment: 12 pages, 10 figures. Final published version

Pulsar timing arrays (PTAs) can detect disturbances in the fabric of spacetime on a galactic scale by monitoring the arrival time of pulses from millisecond pulsars (MSPs). Recent advancements have enabled the use of $\gamma$-ray radiation emitted by MSPs, in addition to radio waves, for PTA experiments. Wave dark matter (DM), a prominent class of DM candidates, can be detected with PTAs due to its periodic perturbations of the spacetime metric. In response to this development, we perform in this Letter a first analysis of applying the $\gamma$-ray PTA to detect the ultralight axion-like wave DM, with the data of Fermi Large Area Telescope (Fermi-LAT). Despite its much smaller collecting area, the Fermi-LAT $\gamma$-ray PTA demonstrates a promising sensitivity potential. We show that the upper limits not far from those of the dedicated radio-PTA projects can be achieved. Moreover, we initiate a cross-correlation analysis using the data of two Fermi-LAT pulsars. The cross-correlation of phases, while carrying key information on the source of the spacetime perturbations, has been ignored in the existing data analyses for the wave DM detection with PTAs. Our analysis indicates that taking this information into account can improve the sensitivity to wave DM by $\gtrsim 50\%$ at masses below $10^{-23}$ eV., Comment: 11 pages, 4 figures. Published version

We propose a new stellar structure of compact stars, the ``cross stars" that consist of a hadronic matter core and a quark matter crust, with an inverted structure compared to the conventional hybrid stars. This distinct stellar structure naturally arises from the quark matter to hadronic matter transition associated with the chemical potential crossing, in the context of the quark matter hypothesis that either strange or up-down quark matter is the ground state of baryonic matter at low pressure. We find that the interplay between the hadronic matter and quark matter compositions of cross stars can help to reconcile the small radii constraints indicated by the LIGO/Virgo GW170817 event, the large radii constraints set for massive compact stars by recent NICER X-ray observations, and the recent observation of the most-massive pulsar PSR J0952-0607. This leaves more space open for the equation of states of both hadronic matter and quark matter., Comment: 10 pages, 6 figures. Published version. Typo fixed

Pulsar timing arrays (PTAs) consisting of widely distributed and well-timed millisecond pulsars can serve as a galactic interferometer to measure gravitational waves. With the same data acquired for PTAs, we propose to develop pulsar polarization arrays (PPAs), to explore astrophysics and fundamental physics. As in the case of PTAs, PPAs are best suited to reveal temporal and spatial correlations at large scales that are hard to mimic by local noise. To demonstrate the physical potential of PPAs, we consider detection of ultralight axion-like dark matter (ALDM), through cosmic birefringence induced by its Chern-Simon coupling. Because of its tiny mass, the ultralight ALDM can be generated as a Bose-Einstein condensate, characterized by a strong wavy nature. Incorporating both temporal and spatial correlations of the signal, we show that PPAs have a potential to probe the Chern-Simon coupling up to $\sim 10^{-14}-10^{-17}$GeV$^{-1}$, with a mass range $\sim 10^{-27} - 10^{-21}$eV., Comment: 11 pages, 4 figures; v2: matches version published in Physical Review Letters, pulsar number for the optimal PPA changed, Fig.2 updated, Supplementary Materials added

Primordial black holes have been considered as an attractive dark matter candidate, whereas some of the predictions heavily rely on the near-horizon physics that remains to be tested experimentally. As a concrete alternative, thermal 2-2-holes closely resemble black holes without event horizons. Being a probable endpoint of gravitational collapse, they not only provide a resolution to the information loss problem, but also naturally give rise to stable remnants. Previously, we have considered primordial 2-2-hole remnants as dark matter. Due to the strong constraints from a novel phenomenon associated with remnant mergers, only small remnants with close to the Planck mass can constitute all of dark matter. In this paper, we examine the scenario that the majority of dark matter consists of particles produced by the evaporation of primordial 2-2-holes, whereas the remnant contribution is secondary. The products with light enough mass may contribute to the number of relativistic degrees of freedom in the early universe, which we also calculate. Moreover, 2-2-hole evaporation can produce particles that are responsible for the baryon asymmetry. We find that baryogenesis through direct B-violating decays or through leptogenesis can both be realized. Overall, the viable parameter space for the Planck remnant case is similar to primordial black holes with Planck remnants. Heavier remnants, on the other hand, lead to different predictions, and the viable parameter space remains large even when the remnant abundance is small., Comment: 34 pages, 8 figures; more added for discussion, matches version to be published in CPC

Quark matter with only $u$ and $d$ quarks ($ud$QM) might be the ground state of baryonic matter at large baryon number $A>A_{\rm min}$. With $A_{\rm min}\gtrsim 300$, this has no direct conflict with the stability of ordinary nuclei. An intriguing test of this scenario is to look for quantum nucleation of $ud$QM inside neutron stars due to their large baryon densities. In this paper, we study the transition rate of cold neutron stars to $ud$ quark stars ($ud$QSs) and the astrophysical implications, considering the relevant theoretical uncertainties and observational constraints. It turns out that a large portion of parameter space predicts an instantaneous transition, and so the observed neutron stars are mostly $ud$QSs. We find this possibility still viable under the recent gravitational wave and pulsar observations, although there are debates on its compatibility with some observations that involve complicated structure of quark matter. The tension could be partially relieved in the two-families scenario, where the high-mass stars ($M\gtrsim2 M_{\odot}$) are all $ud$QSs and the low-mass ones ($M\sim1.4\, M_{\odot}$) are mostly hadronic stars. In this case, the slow transition of the low-mass hadronic stars points to a very specific class of hadronic models with moderately stiff EOSs, and $ud$QM properties are also strongly constrained., Comment: 26 pages, 11 figures

Primordial black holes that survive until the present have been considered as a dark matter candidate. In this paper we argue that primordial 2-2-hole remnants provide a more promising and testable option. 2-2-holes arise in quadratic gravity as a new family of classical solutions for ultracompact matter distributions and they possess the black hole exterior without an event horizon. They may serve as the endpoint of gravitational collapse, providing a resolution for the information loss problem. Intriguing thermodynamic behavior is found for these objects when sourced by a thermal gas. A large 2-2-hole radiates with a Hawking-like temperature and exhibits an entropy-area law. At a late stage, the evaporation slows down and essentially stops as the mass asymptotically approaches a minimal value. This remnant mass is determined by a fundamental scale in quadratic gravity. We study the cosmological and astrophysical implications of having these remnants as dark matter and derive the corresponding constraints. A distinctive phenomenon associated with remnant mergers occurs, predicting fluxes of high-energy astrophysical particles due to the spectacular evaporation of the merger product. Measurements of high-energy photon and neutrino fluxes could possibly bound the remnant mass to be not far above the Planck mass. Early-universe physics, on the other hand, requires that 2-2-holes quickly evolve into the remnant state after formation, putting an upper bound on the formation mass., Comment: 33 pages, 10 figures

We are entering a new era to test the strong gravity regime around astrophysical black holes. The possibility that they are actually horizonless ultracompact objects and then free from the information loss paradox can be examined more closely with observational data. In this paper, we systematically develop a thermal gas model of the 2-2-hole in quadratic gravity, as one step further to look for more tractable models of black hole mimickers. Concrete predictions for departures from black holes are made all the way down to the high curvature interior. The simple form of matter further enables an explicit study of the relation between geometry and thermodynamics. Within this unified framework, we identify notably different behaviors at two limits. On one side is the astrophysically large 2-2-hole, as characterized by a minuscule deviation outside the would-be horizon and a highly squeezed interior along the radial direction. Anomalous features of black hole thermodynamics emerge from the ordinary gas. On the other side is the minimal 2-2-hole with an isotropic and shrinking interior, which behaves more like a normal thermodynamic system. This brings a new perspective to the related theoretical questions as well as phenomenological implications., Comment: 25 pages, 3 figures, 1 table; minor corrections, matches published version

The Higgs self-interactions play a crucial role for exploring the underlying mechanism of electroweak symmetry breaking and the nature of the phase transition involved. In this article, we propose to probe the quartic Higgs self-interaction at lepton and hadron colliders, via the di-Higgs productions. We analyze the contributions of the quartic Higgs coupling, including the renormalization of the cubic Higgs coupling and the modification of the $VVhh$ form factor, to the vector-boson-fusion and the vector-boson associated di-Higgs productions at one-loop level. Such an effect is independent of the choice of gauge-fixing, if the quartic Higgs coupling is decoupled from the other ones in the contexts considered. Notably, a combination of these two di-Higgs productions is important for optimizing the collider sensitivities to probe the quartic Higgs coupling. With this guideline, we explore the ILC and CLIC sensitivities, and find that the ILC has a potential to measure the quartic Higgs coupling, normalized by its SM value, with a precision of $\sim \pm 25$ (500 GeV, 4 ab$^{-1}$ + 1 TeV, 2.5 ab$^{-1}$) and $\sim \pm20$ (500 GeV, 4 ab$^{-1}$ + 1 TeV, 8 ab$^{-1}$), at $1\sigma$ C.L., after marginalizing the cubic Higgs coupling in the $\chi^2$ analysis. The dependence on the renormalization scheme of the cubic Higgs coupling is discussed., Comment: 18 pages, 8 figures, 5 tables. Typos fixed, Fig. 8 updated, references added

If quark matter is energetically favored over nuclear matter at zero temperature and pressure then it has long been expected to take the form of strange quark matter (SQM), with comparable amounts of $u$, $d$, $s$ quarks. The possibility of quark matter with only $u$, $d$ quarks ($ud$QM) is usually dismissed because of the observed stability of ordinary nuclei. However we find that $ud$QM generally has lower bulk energy per baryon than normal nuclei and SQM. This emerges in a phenomenological model that describes the spectra of the lightest pseudoscalar and scalar meson nonets. Taking into account the finite size effects, $ud$QM can be the ground state of baryonic matter only for baryon number $A>A_\textrm{min}$ with $A_\textrm{min}\gtrsim 300$. This ensures the stability of ordinary nuclei and points to a new form of stable matter just beyond the periodic table., Comment: 5 pages, 4 figures, version to appear in Physical Review Letters

Searching for new Higgs particle beyond the observed light Higgs boson h(125GeV) will unambiguously point to new physics beyond the standard model. We study the resonant production of a CP-even heavy Higgs state $H^0$ in the di-Higgs channel via, $gg\to H^0\to h^0h^0\to WW^*WW^*$, at the LHC Run-2 and the high luminosity LHC (HL-LHC). We analyze two types of the $4W$ decay modes, one with the same-sign di-leptons ($4W\to\ell^\pm\nu\ell^\pm\nu 4q$) and the other with tri-leptons ($4W\to\ell^\pm\nu\ell^\mp\nu\ell^\pm\nu 2q$). We perform a full simulation for the signals and backgrounds, and estimate the discovery potential of the heavy Higgs state at the LHC Run-2 and the HL-LHC, in the context of generical two-Higgs-doublet models (2HDM). We determine the viable parameter space of the 2HDM as allowed by the theoretical constraints and the current experimental limits. We systematically analyze the allowed parameter space of the 2HDM which can be effectively probed by the heavy Higgs searches of the LHC, and further compare this with the viable parameter region under the current theoretical and experimental bounds., Comment: v3: JHEP published version, 34pp, 10 Figs(36 plots) and 9 Tables. Only minor typos fixed, references added. v2: JHEP version. All results and conclusions un-changed, discussions and references added. (This update is much delayed due to author's traveling and flu.)

We propose that the SU(2) x SU(2) x U(1) (aka G221) models could provide us a 750 GeV scalar resonance that may account for the diphoton excess observed at the LHC while satisfying present collider constraints. The neutral component of the $SU(2)_R$ scalar multiplet can be identified as the 750 GeV scalar. In the lepto-phobic and fermio-phobic G221 models the new charged gauge boson W' could be light, and we find that the diphoton decay width could be dominated by the loop contribution from the $W'$. To initiate gluon fusion production, it is necessary to extend the G221 symmetry to the Pati-Salam and SO(10) symmetry. We investigate the possibilities that the light colored scalars or vectorlike fermions survive in the SO(10) theory and provide large gluon fusion rate for the diphoton signature. It is possible to test the G221 interpretation by direct searches of W' using the multi-gauge boson production channel at the Run 2 LHC., Comment: 26 pages, 3 figures, 2 tables

LHC Run-2 has provided intriguing di-photon signals of a new resonance around 750GeV, which, if not due to statistical fluctuations, must call for new physics beyond the standard model (SM) at TeV scale. We propose a minimal extension of the SM with a complex singlet scalar $\mathcal{S}$ and a doublet of vector-like quarks. The scalar sector respects CP symmetry, with its CP-odd imaginary component $\chi$ providing a natural dark matter (DM) candidate. The real component of $\mathcal{S}$ serves as the new resonance (750GeV) and explains the diphoton excess of the LHC Run-2. The new scalar degrees of freedom of $\mathcal{S}$ help to stabilize the Higgs vacuum, and can realize the Higgs inflation around GUT scale, consistent with the current cosmology observations. We construct two representative samples A and B of our model for demonstration. We study the mono-jet signals of the DM production from invisible decays Re$(\mathcal{S}) \to \chi\chi$ at the LHC Run-2. We further derive the DM relic density bound, and analyze the constraints from direct and indirect DM detections., Comment: Phys.Lett.B Final Version. 16pp (7 Figs + 2 Tables). Only minor text refinements, references added

Constrained flavor violation is a recent proposal for predicting the down-quark Yukawa matrix in terms of those for up quarks and charged leptons. We study the viability of CFV with respect to its predictions for the lepton mass ratios, showing that this remains a challenge, and suggest some possible means for improving this shortcoming. We then extend CFV to include neutrinos, and show that it leads to interesting predictions for hierachical heavy neutrinos, and leptogenesis dominated by decays of the second heaviest one ("N2 leptogenesis"), as well as the possibility of low-scale leptoquark-mediated exotic decays., Comment: 13 pages, 7 figures; v.2: published version, reorganized and clarified leptogenesis section

Despite the discovery of a Higgs boson h(125GeV) at the LHC Run-1, its self-interaction has fully evaded direct experimental probe so far. Such self-interaction is vital for electroweak symmetry breaking, vacuum stability and electroweak phase transition, and Higgs inflation. It is a most likely place to encode new physics beyond the standard model. We parametrize such new physics by model-independent dimension-6 effective operators, and study their tests via Higgs pair production at hadron colliders. We analyze three major di-Higgs production channels at parton level, and compare the parameter-dependence of total cross sections and kinematic distributions at the LHC(14TeV) and pp(100TeV) hadron collider. We further perform full simulations for the di-Higgs production channel $gg\to hh \to b\bar{b}\gamma\gamma$ and its backgrounds at the pp(100TeV) hadron collider. We construct four kinds of benchmark points, and study the sensitivities to probing different regions of the parameter space of cubic Higgs interactions. We find that for one-parameter analysis and with a 3/ab (30/ab) integrated luminosity, the $gg\to hh \to b\bar{b}\gamma\gamma$ channel can measure the SM cubic Higgs coupling and the derivative cubic Higgs coupling to an accuracy of about 13% (4.2%) and 5% (1.6%), respectively., Comment: 35pp (13 Figs, 2 Tables), PRD Journal Version, all results unchanged, only minor refinements, references added

We consider possible extensions of the standard model that are not only completely asymptotically free, but are such that the UV fixed point is completely UV attractive. All couplings flow towards a set of fixed ratios in the UV. Motivated by low scale unification, semi-simple gauge groups with elementary scalars in various representations are explored. The simplest model is a version of the Pati-Salam model. The Higgs boson is truly elementary but dynamical symmetry breaking from strong interactions may be needed at the unification scale. A hierarchy problem, much reduced from grand unified theories, is still in need of a solution., Comment: 26 pages. Published version, typos corrected

So far all evidences of dark matter (DM) come from astrophysical and cosmological observations, due to gravitational interactions of the DM. It is possible that the true DM particle in the universe joins gravitational interactions only, but nothing else. Such a Gravitational DM (GDM) acts as a weakly interacting massive particle (WIMP), which is conceptually simple and attractive. In this work, we explore this direction by constructing the simplest scalar GDM particle $\chi_s$. It is a $Z_2$ odd singlet under the standard model (SM) gauge group, and naturally joins the unique dimension-4 interaction with Ricci curvature, $\xi_s \chi_s^2 R$, where $\xi_s$ is the dimensionless nonminimal coupling. We demonstrate that this gravitational interaction $\xi_s \chi_s^2 R$, together with Higgs-curvature nonminimal coupling term $\xi_h H^\dag H R$, induces effective couplings between $\chi_s^2$ and SM fields which can account for the observed DM thermal relic abundance. We analyze the annihilation cross sections of GDM particles and derive the viable parameter space for realizing the DM thermal relic density. We further study the direct/indirect detections and the collider signatures of such a scalar GDM. These turn out to be highly predictive and testable., Comment: 33pp, JCAP Final Version. Only minor rewordings, references added

In this work, we examine the possibility of realizing a strongly first-order electroweak phase transition within the minimal classically scale invariant extension of the standard model (SM), previously proposed and analyzed as a potential solution to the hierarchy problem. By introducing one complex singlet scalar and three right-handed Majorana neutrinos, the scenario was successfully capable of achieving a radiative breaking of the electroweak symmetry (Coleman-Weinberg Mechanism), inducing non-zero masses for the SM neutrinos (seesaw mechanism), presenting a pseudoscalar dark matter candidate, and predicting the existence of a second $CP$-even boson in addition to the 125 GeV scalar. We construct the full finite-temperature one-loop effective potential of the model, including the resummed thermal daisy loops, and demonstrate that finite-temperature effects induce a first-order electroweak phase transition. Requiring the thermally-driven first-order phase transition to be sufficiently strong further constrains the model's parameter space; in particular, an $\mathcal O(0.01)$ fraction of the dark matter in the universe may be simultaneously accommodated with a strongly first-order electroweak phase transition. Moreover, such a phase transition disfavors right-handed Majorana neutrino masses above several hundreds of GeV, confines the pseudoscalar dark matter masses to $\sim 1$-2 TeV, predicts the mass of the second $CP$-even scalar to be $\sim 100$-300 GeV, and requires the mixing angle between the $CP$-even components of the SM doublet and the complex singlet to lie within the range $0.2 \lesssim \sin\omega \lesssim 0.4$. The obtained results are displayed in comprehensive exclusion plots, identifying the viable regions of the parameter space. Many of these predictions lie within the reach of the next LHC run., Comment: 18 pages, 9 figures. Published version, typos corrected, references added

In a previous work, a classically scale invariant extension of the standard model was proposed, as a potential candidate for resolving the hierarchy problem, by minimally introducing a complex gauge singlet scalar, and generating radiative electroweak symmetry breaking by means of the Coleman- Weinberg Mechanism. Postulating the singlet sector to respect the CP-symmetry, the existence of a stable pseudoscalar dark matter candidate with a mass in the TeV range was demonstrated. More- over, the model predicted the presence of another physical CP-even Higgs boson (with suppressed tree-level couplings), in addition to the 125 GeV scalar discovered by the LHC. The viable region of the parameter space was determined by various theoretical and experimental considerations. In this work, we continue to examine the phenomenological implications of the proposed minimal sce- nario by considering the constraints from the dark matter relic density, as determined by the Planck collaboration, as well as the direct detection bounds from the LUX experiment. Furthermore, we investigate the implications of the collider Higgs searches for the additional Higgs boson. Our results are comprehensively demonstrated in unified exclusion plots, which analyze the viable region of the parameter space from all relevant angles, demonstrating the testability of the proposed scenario., Comment: Published version with a slight adjustment of the title per journal's suggestion

We discuss the properties and LHC phenomenology of a potentially discoverable heavy scalar boson ($s$) that arises in the context of the renormalizable coloron model; the model also contains a light scalar, $h$, identifiable with the 125 GeV state discovered by the LHC. These two scalar mass eigenstates are admixtures of a weak doublet gauge eigenstate and a weak singlet gauge eigenstate. A previous study set exclusion limits on the heavy $s$ scalar, using the stability of the scalar potential, unitarity, electroweak precision tests, LHC searches for the 125 GeV Higgs; it also briefly discussed the $\sqrt{s} = 7,8$ TeV LHC searches for a heavy Higgs. In this work, we show how the projected LHC sensitivity at $\sqrt{s} = 14$ TeV to the presence of a heavy Higgs and to the detailed properties of the 125 GeV Higgs will further constrain the properties of the new heavy $s$ scalar. Since the renormalizable coloron model may contain spectator fermions to remove anomalies, we examine several representative scenarios with different numbers of spectator fermions. Our results are summarized in plots that overlay the current exclusion limits on the $s$ boson with the projected sensitivity of the $\sqrt{s} = 14$ TeV LHC to the new state. We find that the upcoming LHC searches should be sensitive to an $s$ scalar of mass less than 1 TeV for essentially all of the model parameter space in which the $h$ state differs from the Higgs boson of the SM. More precisely, unless the mixing between the weak doublet and weak singlet gauge-eigenstate scalars is zero, the 14 TeV LHC will be sensitive to the presence of the non-standard heavy $s$ state that is characteristic of the renormalizable coloron model., Comment: 13 pages, 22 embedded figures

We study gravitational interaction of Higgs boson through the unique dimension-4 operator $\xi H^\dag H R$, with $H$ the Higgs doublet and $R$ the Ricci scalar curvature. We analyze the effect of this dimensionless nonminimal coupling $\xi$ on weak gauge boson scattering in both Jordan and Einstein frames. We explicitly establish the longitudinal-Goldstone boson equivalence theorem with nonzero $\xi$ coupling in both frames, and analyze the unitarity constraints. We study the $\xi$-induced weak boson scattering cross sections at O(1-30)TeV scales, and propose to probe the Higgs-gravity coupling via weak boson scattering experiments at the LHC(14TeV) and the next generation pp colliders (50-100TeV). We further extend our study to Higgs inflation, and quantitatively derive the perturbative unitarity bounds via coupled channel analysis, under large field background at the inflation scale. We analyze the unitarity constraints on the parameter space in both the conventional Higgs inflation and the improved models in light of the recent BICEP2 data., Comment: 40pp, JCAP Final Version. Use jcappub.sty, only minor rewordings, references added

We construct a minimal viable extension of the standard model (SM) with classical scale symmetry. Its scalar sector contains a complex singlet in addition to the SM Higgs doublet. The scale-invariant and CP-symmetric Higgs potential generates radiative electroweak symmetry breaking a la Coleman-Weinberg, and gives a natural solution to the hierarchy problem, free from fine-tuning. Besides the 125GeV SM-like Higgs particle, it predicts a new CP-even Higgs (serving as the pseudo-Nambu-Goldstone boson of scale symmetry breaking) and a CP-odd scalar singlet (providing the dark matter candidate) at weak scale. We systematically analyze experimental constraints from direct LHC Higgs searches and electroweak precision tests, as well as theoretical bounds from unitarity, triviality and vacuum stability. We demonstrate the viable parameter space, and discuss implications for new Higgs and dark matter (DM) searches at the upcoming LHC runs and for the on-going direct detections of DM., Comment: Phys.Lett.B final version. Only minor refinements

The renormalizable coloron model is the minimal extension of the standard model color sector, in which the color gauge group is enlarged to SU(3)_{1c} x SU(3)_{2c}. In this paper we discuss the constraints on this model derived from the requirements of vacuum stability, tree-level unitarity, electroweak precision measurements, and from LHC measurements of the properties of the observed Higgs-like scalar boson. The combination of these theoretical and experimental considerations strongly constrains the allowed parameter space. (Erratum appended, March 2014.), Comment: 20 pages, pdf included figures. Brief phenomenological analysis of additional scalar s-boson added. Erratum appended: an error in the Higgs-boson gluon-fusion production amplitude arising from the new colored states is corrected, resulting in stronger constraints on the model parameter space

With the LHC discovery of a 125 GeV Higgs-like boson, we study gravitational interaction of the Higgs boson via the unique dimension-4 operator involving Higgs doublet and scalar curvature, $\,\xi H^\dag H R\,$, with nonminimal coupling $\,\xi\,$. This Higgs portal term can be transformed away in Einstein frame and induces gauge-invariant effective interactions in the Higgs sector. We study the weak boson scattering in Einstein frame, and explicitly demonstrate the longitudinal-Goldstone boson equivalence theorem in the presence of $\,\xi\,$ coupling. With these, we derive unitarity bound on the Higgs gravitational coupling $\,\xi\,$ in Einstein frame, which is stronger than that inferred from the current LHC Higgs measurements. We further study $\xi$-dependent weak boson scattering cross sections at TeV scale, and propose a new LHC probe of the Higgs-gravity coupling $\,\xi\,$ via weak boson scattering experiments., Comment: 7pp, Phys.Rev.D Published Version. All results + conclusions un-changed. Only minor rewording to clarify the Importance of this work

This paper completes the study of the next-to-leading order (NLO) QCD corrections to massive color-octet vector boson production at the LHC and Tevatron. The massive color-octet vector bosons are generically referred to as colorons. Building on our previous calculation of quark-initiated coloron production at NLO, we use the pinch technique to investigate coloron production via gluon fusion. We demonstrate that this one-loop production amplitude is finite, and find that its numerical contribution to coloron production is typically four orders of magnitude smaller than the contribution from quark annihilation. Coloron production via gluon fusion is therefore only relevant if the colorons are (nearly) fermiophobic. We then present extensive plots and tables of our full results for NLO coloron production at the Tevatron and the LHC., Comment: 22 pages, pdf figures included (references added)

Weakly Interacting Massive Particles (WIMPs) are the candidates of dark matter in our universe. Up to now any direct interaction of WIMP with nuclei has not been observed yet. The exclusion limits of the spin-independent cross section of WIMP-nucleon which have been experimentally obtained is about 10^{-7}pb at high mass region and only 10^{-5}pb} at low mass region. China Jin-Ping underground laboratory CJPL is the deepest underground lab in the world and provides a very promising environment for direct observation of dark matter. The China Dark Matter Experiment (CDEX) experiment is going to directly detect the WIMP flux with high sensitivity in the low mass region. Both CJPL and CDEX have achieved a remarkable progress in recent two years. The CDEX employs a point-contact germanium semi-conductor detector PCGe whose detection threshold is less than 300 eV. We report the measurement results of Muon flux, monitoring of radioactivity and Radon concentration carried out in CJPL, as well describe the structure and performance of the 1 kg PCGe detector CDEX-1 and 10kg detector array CDEX-10 including the detectors, electronics, shielding and cooling systems. Finally we discuss the physics goals of the CDEX-1, CDEX-10 and the future CDEX-1T detectors., Comment: 36pages,39 figures

We analyze the phenomenology of the top-pion and top-Higgs states in models with strong top dynamics, and translate the present LHC searches for the Standard Model Higgs into bounds on these scalar states. We explore the possibility that the new state at a mass of approximately 125 GeV observed at the LHC is consistent with a neutral pseudoscalar top-pion state. We demonstrate that a neutral pseudoscalar top-pion can generate the diphoton signal at the observed rate. However, the region of model parameter space where this is the case does not correspond to classic topcolor-assisted technicolor scenarios with degenerate charged and neutral top-pions and a top-Higgs mass of order twice the top mass; rather, additional isospin violation would need to be present and the top dynamics would be more akin to that in top seesaw models. Moreover, the interpretation of the new state as a top-pion can be sustained only if the ZZ (four-lepton) and WW (two-lepton plus missing energy) signatures initially observed at the 3? level decline in significance as additional data is accrued., Comment: 25 pages, pdf embedded figures. Submission extensively revised to reflect discovery of a 125 GeV boson

LHC searches for the standard model Higgs Boson in \gamma\gamma\ or \tau\tau\ decay modes place strong constraints on the light technipion state predicted in technicolor models that include colored technifermions. Compared with the standard Higgs Boson, the technipions have an enhanced production rate (largely because the technipion decay constant is smaller than the weak scale) and also enhanced branching ratios into di-photon and di-tau final states (largely due to the suppression of WW decays of the technipions). Recent ATLAS and CMS searches for Higgs bosons exclude the presence of technipions with masses from 110 GeV to nearly 2m_t in technicolor models that (a) include colored technifermions (b) feature topcolor dynamics and (c) have technicolor groups with three or more technicolors (N_{TC} > 3)., Comment: 15 pages, pdf figures embedded. Contribution to KMI Inauguration Conference "Quest for the Origin of Particles and the Universe" (KMIIN), 24-26 Nov. 2011, KMI, Nagoya University

LHC searches for the standard model Higgs Boson in di-photon or di-tau decay modes place strong constraints on the light top-pion state predicted in technicolor models that include colored technifermions. Compared with the standard Higgs Boson, the top-pions have an enhanced production rate (largely because the technipion decay constant is smaller than the weak scale) and also enhanced branching ratios into di-photon and di-tau final states (largely due to the suppression of WW decays of the technipions). These factors combine to make the technipions more visible in both channels than a standard model Higgs would be. Hence, the recent ATLAS and CMS searches for Higgs bosons exclude the presence of technipions with masses from 110 GeV to nearly twice the top-quark mass in technicolor models that (a) include colored technifermions (b) feature topcolor dynamics and (c) have technicolor groups with three or more technicolors. For certain models, the limits also apply out to higher technipion masses or down to the minimum number of technicolors. The limits may be softened somewhat in models where extended technicolor plays a significant role in producing the top quark's mass. Additional LHC data on di-tau and di-photon final states will be extremely valuable in further exploring technicolor parameter space., Comment: 15 pages, 5 figures, PDF-LaTeX