We present a simple solution to the little hierarchy problem in the minimal supersymmetric standard model: a vectorlike fourth generation. With $\mathcal{O}(1)$ Yukawa couplings for the new quarks, the Higgs mass can naturally be above 114 GeV. Unlike a chiral fourth generation, a vectorlike generation can solve the little hierarchy problem while remaining consistent with precision electroweak and direct production constraints, and maintaining the success of the grand unified framework. The new quarks are predicted to lie between $\sim 300–600\mathrm{GeV}$ and will thus be discovered or ruled out at the LHC. This scenario suggests exploration of several novel collider signatures.

In an extension of the standard model with a scalar color octet, the possibility of the strongly first-order electroweak phase transition is studied by examining the finite-temperature effective Higgs potential at the one-loop level. It is found that there are wide regions in the parameter space that allow the strongly first-order electroweak phase transition, where the Higgs boson mass is larger than the experimental lower bound of 115 GeV, and the masses of the scalar color octet is around 200 GeV. The parameter regions may be explored at the LHC with respect to the electroweak phase transition.

Recently, a new class of models describing the quark mass hierarchy has been introduced. In this class, while the $t$ quark plays a minor role in electroweak symmetry breaking, it is crucial in providing the quark mass hierarchy. In this paper, we analyze the dynamics of a particular model in this class, in which the $b^{\prime }$ and $t^{\prime }$ quarks of the fourth family are mostly responsible for dynamical electroweak symmetry breaking. The low energy effective theory in this model is derived. It has a clear signature, a $2+1$ structure of composite Higgs doublets: two nearly degenerate ${\Phi }_{b^{\prime }}\sim {\overline{b}}_R^{\prime }(t^{\prime },b^{\prime }{)}_L$ and ${\Phi }_{t^{\prime }}\sim {\overline{t}}_R^{\prime }(t^{\prime },b^{\prime }{)}_L$, and a heavier top-Higgs resonance ${\Phi }_t\sim {\overline{t}}_R(t,b{)}_L$. The properties of these composites are described in detail, and it is shown that the model satisfies the electroweak precision data constraints. The signatures of these composites at the Large Hadron Collider are briefly discussed.

We calculate the radiative decay widths, two-photon ($\gamma \gamma$) and one-photon–one-vector meson ($V\gamma$), of the dynamically generated resonances from vector-meson–vector-meson interaction in a unitary approach based on the hidden-gauge Lagrangians. In the present paper we consider the following dynamically generated resonances: $f_0(1370)$, $f_0(1710)$, $f_2(1270)$, $f_2^{\prime }(1525)$, $K_2^{*}(1430)$, two $\mathrm{\text{strangeness}}=0$ and $\mathrm{\text{isospin}}=1$ states, and two $\mathrm{\text{strangeness}}=1$ and $\mathrm{\text{isospin}}=1/2$ states. For the $f_0(1370)$ and $f_2(1270)$ we reproduce the previous results for the two-photon decay widths and further calculate their one-photon–one-vector decay widths. For the $f_0(1710)$ and $f_2^{\prime }(1525)$ the calculated two-photon decay widths are found to be consistent with data. The ${\rho }^0\gamma$, $\omega \gamma$ and $\varphi \gamma$ decay widths of the $f_0(1370)$, $f_2(1270)$, $f_0(1710)$, $f_2^{\prime }(1525)$ are compared with the results predicted by other approaches. The $K^{*+}\gamma$ and $K^{*0}\gamma$ decay rates of the $K_2^{*}(1430)$ are also calculated and compared with the results obtained in the framework of the covariant oscillator quark model. The results for the two states with $\mathrm{\text{strangeness}}=0$, $\mathrm{\text{isospin}}=1$ and two states with $\mathrm{\text{strangeness}}=1$, $\mathrm{\text{isospin}}=1/2$ are predictions that need to be tested by future experiments.

We calculate the relativistic correction to $J/\psi$ production in the color-singlet process $e^{+}{e}^{-}\to J/\psi +gg$ at $B$ factories. We employ the nonrelativistic QCD factorization approach, where the short-distance coefficients are calculated perturbatively and the long-distance matrix elements are extracted from the decays of $J/\psi$ into $e^{+}{e}^{-}$ and light hadrons. We find that the $O(v^2)$ relativistic correction can enhance the cross section by a factor of 20–30%, comparable to the enhancement due to the $O({\alpha }_s)$ radiative correction obtained earlier. Combining the relativistic correction with the QCD radiative correction, we find that the color-singlet contribution to $e^{+}{e}^{-}\to J/\psi +gg$ can saturate the latest observed cross section $\sigma (e^{+}{e}^{-}\to J/\psi +X_{\mathrm{non}\mathrm{\text{−}}c\overline{c}})=0.43\pm 0.09\pm 0.09\mathrm{pb}$ by Belle, thus leaving little room to the color-octet contributions. This gives a very stringent constraint on the color-octet contribution, and may imply that the values of color-octet matrix elements are much smaller than expected earlier by using the naive velocity scaling rules or extracted from fitting experimental data with the leading-order calculations.

We study the light quark mass dependence of the $f_0(600)$, $\kappa (800)$, $\rho (770)$, and $K^{*}(892)$ resonance parameters generated from elastic meson-meson scattering using unitarized one-loop chiral perturbation theory. First, we show that it is possible to fit simultaneously all experimental scattering data up to 0.8–1 GeV together with lattice results on decay constants and scattering lengths up to a pion mass of 400 MeV, using chiral parameters compatible with existing determinations. Then, the strange and nonstrange quark masses are varied from the chiral limit up to values of interest for lattice studies. In these amplitudes, the mass and width of the $\rho (770)$ and $K^{*}(892)$ present a similar and smooth quark mass dependence. In contrast, both scalars present a similar nonanalyticity at high quark masses. Nevertheless, the $f_0(600)$ dependence on the nonstrange quark mass is stronger than for the $\kappa (800)$ and the vectors. We also confirm the lattice assumption of quark mass independence of the vector two-meson coupling that, in contrast, is violated for scalars. As a consequence, vector widths are very well approximated by the Kawarabayashi-Suzuki-Riazuddin-Fayyazuddin relation, and their masses are shown to scale like their corresponding meson decay constants.

We study the implications of the simultaneous existence of a texture zero and a vanishing minor in the neutrino mass matrix. There are 36 possible texture structures of this type, 21 of which reduce to two texture zero cases which have, already, been extensively studied. Of the remaining 15 textures only six are allowed by the current data. We examine the phenomenological implications of the allowed texture structures for Majorana type $CP$-violating phases, 1-3 mixing angle, and Dirac type $CP$-violating phase. All these possible textures can be generated through the seesaw mechanism and realized in the framework of discrete Abelian flavor symmetry. We present the symmetry realization of these texture structures.

Using data collected on the $\psi (3770)$ resonance and near the $D_s^{*\pm }{D}_s^{\mp }$ peak production energy by the CLEO-c detector, we study the decays of the possible $D\to PP$ modes and report measurements of or upper limits on all branching fractions for Cabibbo-favored, singly Cabibbo-suppressed, and doubly Cabibbo-suppressed $D\to PP$ decays except modes involving $K_L^0$ (and except $D^0\to K^{+}{\pi }^{-}$). We normalize with respect to the Cabibbo-favored $D$ modes, $D^0\to K^{-}{\pi }^{+}$, $D^{+}\to K^{-}{\pi }^{+}{\pi }^{+}$, and $D_s^{+}\to K^{+}{K}_S^0$.

We have used a sample of $\gamma +3$ jets events collected by the D0 experiment with an integrated luminosity of about $1{\mathrm{fb}}^{-1}$ to determine the fraction of events with double parton scattering ($f_{\mathrm{DP}}$) in a single $p\overline{p}$ collision at $\sqrt{s}=1.96\mathrm{TeV}$. The DP fraction and effective cross section (${\sigma }_{\mathrm{eff}}$), a process-independent scale parameter related to the parton density inside the nucleon, are measured in three intervals of the second (ordered in $p_T$) jet transverse momentum $p_T^{\mathrm{jet}2}$ within the range $15\le p_T^{\mathrm{jet}2}\le 30\mathrm{GeV}$. In this range, $f_{\mathrm{DP}}$ varies between $0.23\le f_{\mathrm{DP}}\le 0.47$, while ${\sigma }_{\mathrm{eff}}$ has the average value ${\sigma }_{\mathrm{eff}}^{\mathrm{ave}}=16.4\pm 0.3(\mathrm{stat})\pm 2.3(\mathrm{syst})\mathrm{mb}$.

With the recent possible signal of dark matter from the CDMS II experiment, the $Z^{\prime }$ mass of a new version of the dark left-right gauge model (DLRM II) is predicted to be at around a TeV. As such, it has an excellent discovery prognosis at the operating Large Hadron Collider.

A detection or nondetection of primordial non-Gaussianity by using the cosmic microwave background radiation (CMB) data is crucial not only to discriminate inflationary models but also to test alternative scenarios. Non-Gaussianity offers, therefore, a powerful probe of the physics of the primordial Universe. The extraction of primordial non-Gaussianity is a difficult enterprise since several effects of a nonprimordial nature can produce non-Gaussianity. Given the far-reaching consequences of such a non-Gaussianity for our understanding of the physics of the early Universe, it is important to employ a range of different statistical tools to quantify and/or constrain its amount in order to have information that may be helpful for identifying its causes. Moreover, different indicators can in principle provide information about distinct forms of non-Gaussianity that can be present in CMB data. Most of the Gaussianity analyses of CMB data have been performed by using part-sky frequency, where the mask is used to deal with the galactic diffuse foreground emission. However, full-sky map seems to be potentially more appropriate to test for Gaussianity of the CMB data. On the other hand, masks can induce bias in some non-Gaussianity analyses. Here we use two recent large-angle non-Gaussianity indicators, based on skewness and kurtosis of large-angle patches of CMB maps, to examine the question of non-Gaussianity in the available full-sky five-year and seven-year Wilkinson Microwave Anisotropy Probe (WMAP) maps. We show that these full-sky foreground-reduced maps present a significant deviation from Gaussianity of different levels, which vary with the foreground-reducing procedures. We also make a Gaussianity analysis of the foreground-reduced five-year and seven-year WMAP maps with a $KQ75$ mask, and compare with the similar analysis performed with the corresponding full-sky foreground-reduced maps. This comparison shows a significant reduction in the levels of non-Gaussianity when the mask is employed, which provides indications on the suitability of the foreground-reduced maps as Gaussian reconstructions of the full-sky CMB.

Models of minimal lepton flavor violation where the seesaw scale is higher than the relevant flavor scale predict that all lepton flavor violation is proportional to the charged lepton Yukawa matrix. If extra vectorlike leptons are within the reach of the LHC, it will be possible to test the resulting predictions in ATLAS/CMS.

Particle physics model building within the context of string theory suggests that further copies of the Higgs boson sector may be expected. Concerns regarding tree-level flavor-changing neutral currents are easiest to allay if little or no couplings of next generation Higgs bosons to standard model fermions are allowed. We detail the resulting general Higgs potential and mass spectroscopy in both a standard model extension and a supersymmetric extension. We present the important experimental constraints from meson-meson mixing, loop-induced $b\to s\gamma$ decays, and LEP2 direct production limits. We investigate the energy range of the valid perturbation theory of these ideas. In the supersymmetric context we present a class of examples that marginally aids the fine-tuning problem for parameter space where the lightest Higgs boson mass is greater than the standard model limit of 114 GeV. Finally, we study collider physics signatures generic to next generation Higgs bosons, with special emphasis on $Ah\to hhZ\to 4b+2l$ signal events, and describe the capability of discovery at the Large Hadron Collider.

We study the region of the QCD phase transition using $2+1$ flavors of domain wall fermions and a ${16}^3\times 8$ lattice volume with a fifth dimension of $L_s=32$. The disconnected light quark chiral susceptibility, quark number susceptibility, and the Polyakov loop suggest a chiral and deconfining crossover transition lying between 155 and 185 MeV for our choice of quark mass and lattice spacing. In this region the lattice scale deduced from the Sommer parameter $r_0$ is $a^{-1}\approx 1.3\mathrm{GeV}$, the pion mass is $\approx 300\mathrm{MeV}$, and the kaon mass is approximately physical. The peak in the chiral susceptibility implies a pseudocritical temperature $T_c=171(10)(17)\mathrm{MeV}$ where the first error is associated with determining the peak location and the second with our unphysical light quark mass and nonzero lattice spacing. The effects of residual chiral symmetry breaking on the chiral condensate and disconnected chiral susceptibility are studied using several values of the valence $L_s$.

The single diffractive cross section for heavy quarks production is calculated at next-to-leading order (for nucleus-nucleus collisions. Such processes are expected to occur at the LHC, where the nuclei involved are lead at $\sqrt{s}=5.5\mathrm{TeV}$ and calcium at $\sqrt{s}=6.3\mathrm{TeV}$. We start using the hard diffractive factorization formalism, taking into account a recent experimental parametrization for the Pomeron structure function (DPDF). Absorptive corrections are accounted for by the multiple Pomeron contributions considering a gap survival probability, where its theoretical uncertainty for nuclear collisions is discussed. We estimate the diffractive ratios for the single diffraction process in nuclear coherent/incoherent collisions at the LHC.

We use a Nambu–Jona-Lasinio type model to investigate the phase diagram of dense quark matter under neutron star conditions in mean-field approximation. The model contains self-consistently determined quark masses and allows for diquark condensation in the scalar as well as in the pseudoscalar channel. The latter gives rise to the possibility of $K^0$ condensation in the color-flavor locked phase. In agreement with earlier studies we find that this ${\mathrm{CFLK}}^0$ phase covers large regions of the phase diagram and that the predominant part of this phase is fully gapped. We show, however, that there exists a region at very low temperatures where the ${\mathrm{CFLK}}^0$ solutions become gapless, possibly indicating an instability towards anisotropic or inhomogeneous phases. The physical significance of solutions with pseudoscalar diquark condensates in the 2SC phase is discussed as well.

The charm quark offers interesting opportunities to cross check the mechanism of $CP$ violation precisely tested in the strange and beauty sectors. In this paper, we exploit the angular and quantum correlations in the $D\overline{D}$ pairs produced through the decay of the $\psi (3770)$ resonance in a charm factory to investigate $CP$-violation in two different ways. We build $CP$-violating observables in $\psi (3770)\to D\overline{D}\to (V_1{V}_2)(V_3{V}_4)$ to isolate specific new physics effects in the charm sector. We also consider the case of $\psi (3770)\to D\overline{D}\to (V_1{V}_2)(K\pi )$ decays, which provide a new way to measure the strong phase difference $\delta$ between Cabibbo- favored and doubly-Cabibbo suppressed $D$ decays required in the determination of the Cabibbo-Kobayashi-Maskawa quark-mixing matrix angle $\gamma$. Neglecting the systematics, we give a first rough estimate of the sensitivities of these measurements at BES-III with an integrated luminosity of $20{\mathrm{fb}}^{-1}$ at $\psi (3770)$ peak and at a future Super $\tau$-charm factory with a luminosity of ${10}^{35}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$.

We study the three-quark static potential in perturbation theory in QCD. A complete next-to-leading order calculation is performed in the singlet, octets, and decuplet channels and the potential exponentiation is demonstrated. The mixing of the octet representations is calculated. At next-to-next-to-leading order, the subset of diagrams producing three-body forces is identified in Coulomb gauge and its contribution to the potential calculated. Combining it with the contribution of the two-body forces, which may be extracted from the quark-antiquark static potential, we obtain the complete next-to-next-to-leading order three-quark static potential in the color-singlet channel.

In this work, we have calculated the tree level color-singlet contribution to the inclusive $J/\psi$ production in ${\rm Y}$ decay of the ${\alpha }_s^5$ order QCD process ${\rm Y}\to J/\psi +c\overline{c}g$ and ${\alpha }^2{\alpha }_s^2$ order QED processes ${\rm Y}\to {\gamma }^{*}\to J/\psi +c\overline{c}$ and ${\rm Y}\to J/\psi +gg$. It is found that the contribution of the QED processes is comparable with that of the QCD process and the numerical results of the QCD process alone are about an order of magnitude smaller than the previous theoretical predictions. Our prediction in total is $4.2\times {10}^{-5}$ which is about an order of magnitude smaller than the recent CLEO measurement on the branching fraction $\mathcal{B}({\rm Y}\to J/\psi +X)$. It indicates that the $J/\psi$ production mechanism in ${\rm Y}$ decay is not well understood and further theoretical work and experimental analysis are still necessary.

We present a measurement of the top quark mass and of the top-antitop ($t\overline{t}$) pair production cross section using $p\overline{p}$ data collected with the CDF II detector at the Tevatron Collider at the Fermi National Accelerator Laboratory and corresponding to an integrated luminosity of $2.9{\mathrm{fb}}^{-1}$. We select events with six or more jets satisfying a number of kinematical requirements imposed by means of a neural-network algorithm. At least one of these jets must originate from a $b$ quark, as identified by the reconstruction of a secondary vertex inside the jet. The mass measurement is based on a likelihood fit incorporating reconstructed mass distributions representative of signal and background, where the absolute jet energy scale (JES) is measured simultaneously with the top quark mass. The measurement yields a value of $174.8\pm 2.4(\mathrm{stat}+\mathrm{JES}{)}_{-1.0}^{+1.2}(\mathrm{syst})\mathrm{GeV}/c^2$, where the uncertainty from the absolute jet energy scale is evaluated together with the statistical uncertainty. The procedure also measures the amount of signal from which we derive a cross section, ${\sigma }_{t\overline{t}}=7.2\pm 0.5(\mathrm{stat})\pm 1.0(\mathrm{syst})\pm 0.4(\mathrm{lum})\mathrm{pb}$, for the measured values of top quark mass and JES.