119282054
Discriminating Different $Z^\prime$s via Asymmetries at the LHC
In practice the asymmetry, which is defined based on the angular distribution of the final states in scattering or decay processes, can be utilized to scrutinize underlying dynamics in and/or beyond the standard model (BSM). As one of the possible BSM physics which might be discovered early at the LHC, extra neutral gauge bosons Z{sup '}'s are theoretically well motivated. Once Z{sup '}'s are discovered at the LHC, it is crucial to discriminate different Z{sup '}'s in various BSM. In principle such a task can be accomplished by measuring the angular distribution of the final states which are produced via Z{sup '}-mediated processes. In the real data analysis, asymmetry is always adopted. In the literature several asymmetries have been proposed at the LHC. Based on these works, we stepped further on to study how to optimize the asymmetries in the left-right model and the sequential standard model, as the examples of BSM. In this paper, we examined four kinds of asymmetries, namely, rapidity-dependent forward-backward asymmetry, oneside forward-backward asymmetry, central charge asymmetry, and edge charge asymmetry (see text for details), with l{sup +}l{sup -} (l=e, {mu}), bb, and tt as the final states. In the calculations with bb and tt finalmore » states, the QCD-induced higher-order contributions to the asymmetric cross section were also included. For each kind of final state, we estimated the four kinds of asymmetries and especially the optimal cut usually associated with the definition of the asymmetry. Our numerical results indicated that the capacity to discriminate Z{sup '} models can be improved by imposing the optimal cuts.« less
118654448
Constraints on the universal varying Yukawa couplings: from SM-like to fermiophobic
A bstractVarying the Standard Model (SM) fermion Yukawa couplings universally by a generic positive scale factor $ ({F_{{Y\,u}}}) $, we study the phenomenological fit to the current available experimental results for the Higgs boson search at hadron colliders. We point out that the Higgs production cross section and its decay branching ratio to γγ can be varied oppositely by $ {F_{{Y{ ~ }u}}} $ to make their product almost invariant. Thus, our scenario and the SM Higgs are indistinguishable in the inclusive H → γγ channel. The current measurements on direct Yukawa coupling strength in the $ H \to b\overline b /\tau \tau $ channel are not precise enough to fix the scale factor $ {F_{{Y{ ~ }u}}} $. The most promising is the vector-boson-fusion channel in which the CMS has already observed possible suppression effect on the Yukawa couplings. Further more, the global χ2 fit of the experimental data can get the optimal value by introducing a suppression factor $ {F_{{Y{ ~ }u}}} \sim {1}/{2} $ on the SM Yukawa couplings.
117142150
New Color-Octet Vector Boson?
Both CDF and D0 at Tevatron reported the measurements of forward-backward asymmetry in top pair production, which showed possible deviation from the standard model QCD prediction. In this paper, we show that a new color-octet massive vector boson with mass just above twice that of top quark can simultaneously account for the asymmetry and differential distribution $d\sigma/dM_{t\bar t}$ in top pair production, without conflict with other measurements for example di-jet production. The new particle can be discovered and studied at the more powerful Large Hadron Collider.
119280152
New color-octet vector boson revisited
Motivated by CDF recent measurements on di-jet invariant mass spectrum where di-jet is associated production with charged leptons ($e/\mu$) and missing energy, we re-examine the previous proposed massive color-octet axial-vector-like boson $Z_c$. Our simulation showed that the di-jet bump around 120-160 GeV can be induced by $Z_c$ with effective coupling $g_{Z_c q \bar q} =0.2 g_s$ (q represents the quark other than top and $g_s$ is the strong coupling constant). Moreover our numerical investigation indicated that the top quark forward-backward asymmetry $A_{FB}^t$ can be reproduced without distorting shape of differential cross section $d\sigma/d M_{t\bar t}$, provided that the $Z_c$ and top quark coupling is appropriately chosen ($g_{Z_c t \bar t} \simeq 4.5 g_{Z_c q \bar q}$). Our results also showed that the theoretical $A_{FB}^t$ as functions of $\Delta y$ and $M_{t\bar t}$ can be consistent with data within $1\sigma$ and $1.8\sigma$ respectively.
119241558
Distinguishing the Color Octet Axial-Vector-like Particle for Top Quark Asymmetry via Color Flow Method at the LHC
Tianjun Li Xia Wan You-kai Wang , and Shou-hua Zhu 1 State Key Laboratory of Theoretical Physics and Kavli Institute for Theoretical Physics China (KITPC), Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, P. R. China School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, P. R. China 3 Institute of Theoretical Physics & State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China 4 Center for High Energy Physics, Peking University, Beijing 100871, China (Dated: May 7, 2014)
118887313
$\mathscr{O}(100 GeV)$ Deci-weak $W^\prime/Z^\prime$ at Tevatron and LHC
Recently Tevatron released their measurements on invariant mass spectrum of electron/positron, as well as the di-jet arising from WW+WZ production with one W leptonically decay. Though the statistics is not significant, there are two bumps around 240 GeV and 120-160 GeV respectively. We proposed that the two bumps correspond to the extra light gauge bosons $Z^\prime$ and $W^\prime$, which couple with quarks with the deci-weak strength. In this brief report, we also simulated di-jet invariant mass distribution at the current running LHC.
15495784
The three-point correlation function of galaxies: comparing halo occupation models with observations
We present models for the three-point correlation function (3PCF) of both dark matter and galaxies. We show that models based on the halo model can reasonably match the dark-matter 3PCF obtained from high-resolution N-body simulations. On small scales (r ≤ 0.5 h -1 Mpc) the 3PCF is sensitive to details regarding the density distributions of dark-matter haloes. On larger scales (r ≥ 2.0 h -1 Mpc) the results are very sensitive to the abundance of the few most prominent haloes. Using the conditional luminosity function, we also construct models for the 3PCF of galaxies, which we test against large mock galaxy samples. The bias of the galaxy distribution with respect to the dark matter, and the finite number of galaxies that can be hosted by individual haloes, significantly reduce the normalized three-point correlation function with respect to that of dark matter. Contrary to the 3PCF of the dark matter, the galaxy 3PCF is much less sensitive to details regarding the spatial number density distribution of galaxies in individual haloes or to the abundance of the few most massive systems. Finally, we show that our model based on the conditional luminosity function is in good agreement with results obtained from the 2-degree Field Galaxy Redshift Survey. In particular, the model nicely reproduces the observational finding that the 3PCF for early-type galaxies is slightly higher than that of late-type galaxies, and that there is no significant dependence of the 3PCF on galaxy luminosity.
22730544
Revised rates for the stellar triple-alpha process from measurement of 12C nuclear resonances.
In the centres of stars where the temperature is high enough, three alpha-particles (helium nuclei) are able to combine to form 12C because of a resonant reaction leading to a nuclear excited state. (Stars with masses greater than approximately 0.5 times that of the Sun will at some point in their lives have a central temperature high enough for this reaction to proceed.) Although the reaction rate is of critical significance for determining elemental abundances in the Universe, and for determining the size of the iron core of a star just before it goes supernova, it has hitherto been insufficiently determined. Here we report a measurement of the inverse process, where a 12C nucleus decays to three alpha-particles. We find a dominant resonance at an energy of approximately 11 MeV, but do not confirm the presence of a resonance at 9.1 MeV (ref. 3). We show that interference between two resonances has important effects on our measured spectrum. Using these data, we calculate the triple-alpha rate for temperatures from 10(7) K to 10(10) K and find significant deviations from the standard rates. Our rate below approximately 5 x 10(7) K is higher than the previous standard, implying that the critical amounts of carbon that catalysed hydrogen burning in the first stars are produced twice as fast as previously believed. At temperatures above 10(9) K, our rate is much less, which modifies predicted nucleosynthesis in supernovae.
119300679
The TT, TB, EB and BB correlations in anisotropic inflation
The ongoing and future experiments will measure the B-mode from different sky coverage and frequency bands, with the potential to reveal non-trivial features in polarization map. In this work we study the TT, TB, EB and BB correlations associated with the B-mode polarization of CMB map in models of charged anisotropic inflation. The model contains a chaotic-type large field complex inflaton which is charged under the U(1) gauge field. We calculate the statistical anisotropies generated in the power spectra of the curvature perturbation, the tensor perturbation and their cross-correlation. It is shown that the asymmetry in tensor power spectrum is a very sensitive probe of the gauge coupling. While the level of statistical anisotropy in temperature power spectrum can be small and satisfy the observational bounds, the interactions from the gauge coupling can induce large directional dependence in tensor modes. This will leave interesting anisotropic fingerprints in various correlations involving the B-mode polarization such as the TB cross-correlation which may be detected in upcoming Planck polarization data. In addition, the TT correlation receives an anisotropic contribution from the tensor sector which naturally decays after l ∼> 100. We expect that the mechanism of using tensor sector to induce asymmetry at low lmore » to be generic which can also be applied to address other low l CMB anomalies.« less
54813770
Uncertain system modeling of SNS RF control system
This paper addresses the modeling problem of the linear accelerator RF system for SNS. The cascade of the klystron and the cavity is modeled as a nominal system. In the real world, high voltage power supply ripple, Lorentz force detuning, microphonics, cavity RF parameter perturbations, distortions in RF components, and loop time delay imperfection exist inevitably, which must be analyzed. The analysis is based on the accurate modeling of the disturbances and uncertainties. In this paper, modern control theory is applied for modeling the disturbances, uncertainties, and for analyzing the closed loop system robust performance.
7325683
Determination of the Effective Electroweak Mixing Angle from Z-Decays
Abstract The effective electroweak mixing angle sin 2 θ w is measured from the production and decay of the Z boson in e+e− interactions. The data sample corresponds to an integrated luminosity of 18pb−1 with about 420 000 hadronic and 40 000 leptonic Z decays. The mixing angle sin 2 θ w is determined from several independent measurements: the leptonic and hadronic cross sections, the forward-backward asymmetries of charged leptons and b-quarks, and the τ-polarization. The results are found to be in good agreement with each other. The value of sin 2 θ w from a fit to the asymmetries in a model independent method is 0.2321±0.0021 and from a global fit to the data in the Standard Model framework is 0.2328±0.0013.