Search

We demonstrate that the $3\sigma$ excess observed by ATLAS in the Z + MET channel can be explained within the context of the MSSM. Using the freedom inherent in the pMSSM, we perform a detailed analysis of the parameter space and find a scenario that describes the excess while simultaneously complying with all other search constraints from the Run I data at 7 and 8 TeV, including the Z + MET analysis by CMS. We generate a small sample of simplified models, using promising models from our existing pMSSM sample as seeds, and study their properties. The successful region is described by the production of 1st/2nd generation squark pairs, followed by their decay into a bino-like neutralino which in turn decays into a Higgsino-like LSP triplet by emitting a Z boson, i.e., $\tilde q\to\tilde B\to\tilde h$ with $\tilde q = \tilde Q_L,\tilde u_R,$ or $\tilde d_R$. The sweet spot for the sparticle spectrum is found to have squark masses in the 500-750 GeV range, with bino masses near 350 GeV with a mass splitting of 150-200 GeV with the Higgsino LSP. If this excess holds, then this scenario predicts that a signal will be observed in the 0l + jets and/or 1l + jets searches in the early operations of Run II., Comment: 20 pages, 11 figures

We study SUSY signatures at the 7, 8 and 14 TeV LHC employing the 19-parameter, R-Parity conserving p(henomenological)MSSM, in the scenario with a neutralino LSP. Our results were obtained via a fast Monte Carlo simulation of the ATLAS SUSY analysis suite. The flexibility of this framework allows us to study a wide variety of SUSY phenomena simultaneously and to probe for weak spots in existing SUSY search analyses. We determine the ranges of the sparticle masses that are either disfavored or allowed after the searches with the 7 and 8 TeV data sets are combined. We find that natural SUSY models with light squarks and gluinos remain viable. We extrapolate to 14 TeV with both 300 fb$^{-1}$ and 3 ab$^{-1}$ of integrated luminosity and determine the expected sensitivity of the jets + MET and stop searches to the pMSSM parameter space. We find that the high-luminosity LHC will be powerful in probing SUSY with neutralino LSPs and can provide a more definitive statement on the existence of natural Supersymmetry., Comment: 41 pages, 27 figures. arXiv admin note: substantial text overlap with arXiv:1307.8444

The 19/20-parameter p(henomenological)MSSM with either a neutralino or gravitino LSP offers a flexible framework for the study of a wide variety of R-parity conserving MSSM SUSY phenomena at the 7, 8 and 14 TeV LHC. Here we present the results of a study of SUSY signatures at these facilities obtained via a fast Monte Carlo 'replication' of the ATLAS SUSY analysis suite. In particular, we show the ranges of the sparticle masses that are either disfavored or remain viable after all of the various searches at the 7 and 8 TeV runs are combined. We then extrapolate to 14 TeV with both 300 fb^-1 and 3 ab^-1 of integrated luminosity and determine the sensitivity of a jets + MET search to the pMSSM parameter space. We find that the high-luminosity LHC performs extremely well in probing natural SUSY models., 42 pages, 28 figures; added 14 TeV results for gravitino and low FT model sets, minor changes, references added. Contributed to the Community Summer Study 2013, Minneapolis, MN July 29 - August 6, 2013

The generalization of the MSSM to the case of four chiral fermion generations (4GMSSM) can lead to significant changes in the phenomenology of the otherwise familiar Higgs sector. In most of the 3GMSSM parameter space, the lighter CP-even $h$ is $\sim 115-125$ GeV and mostly Standard Model-like while $H,A,H^\pm$ are all relatively heavy. Furthermore, the ratio of Higgs vevs, $\tan \beta$, is relatively unconstrained. In contrast to this, in the 4GMSSM, heavy fourth generation fermion loops drive the masses of $h,H,H^\pm$ to large values while the CP-odd boson, $A$, can remain relatively light and $\tan \beta$ is restricted to the range $1/2 \lsim \tan \beta \lsim 2$ due to perturbativity requirements on Yukawa couplings. We explore this scenario in some detail, concentrating on the collider signatures of the light CP-odd Higgs at both the Tevatron and LHC. We find that while $gg \to A$ may lead to a potential signal in the $\tau^+\tau^-$ channel at the LHC, $A$ may first be observed in the $\gamma \gamma$ channel due to a highly loop-enhanced cross section that can be more than an order of magnitude greater than that of a SM Higgs for $A$ masses of $\sim 115-120$ and $\tan\beta, Comment: 20 pages, 7 figures; typos fixed, refs added

We examine the scenario where a leptophobic Z' boson accounts for the excess of events in the Wjj channel as observed by CDF. We assume generation independent couplings for the Z' and obtain allowed regions for the four hadronic couplings using the cross section range quoted by CDF as well as constraints from dijet production at UA2. These coupling regions translate into well-determined rates for the associated production of Z/\gamma+Z' at the Tevatron and LHC, as well as W+Z' at the LHC,that are directly correlated with the Wjj rate observed at the Tevatron. The Wjj rate at the LHC is large and this channel should be observed soon once the SM backgrounds are under control. The rates for Z/\gamma+Z' associated production are smaller, and these processes should not yet have been observed at the Tevatron given the expected SM backgrounds. In addition, we also show that valuable coupling information is obtainable from the distributions of other kinematic variables, e.g., M_{WZ'}, p_T^W, and \cos \theta_W^*. Once detected, these associated production processes and the corresponding kinematic distributions examined here will provide further valuable information on the Z' boson couplings., Comment: 20 pages, 10 figures. Analysis and discussion updated

There are many possibilities for new physics beyond the Standard Model that feature non-standard Higgs sectors. These may introduce new sources of CP violation, and there may be mixing between multiple Higgs bosons or other new scalar bosons. Alternatively, the Higgs may be a composite state, or there may even be no Higgs at all. These non-standard Higgs scenarios have important implications for collider physics as well as for cosmology, and understanding their phenomenology is essential for a full comprehension of electroweak symmetry breaking. This report discusses the most relevant theories which go beyond the Standard Model and its minimal, CP-conserving supersymmetric extension: two-Higgs-doublet models and minimal supersymmetric models with CP violation, supersymmetric models with an extra singlet, models with extra gauge groups or Higgs triplets, Little Higgs models, models in extra dimensions, and models with technicolour or other new strong dynamics. For each of these scenarios, this report presents an introduction to the phenomenology, followed by contributions on more detailed theoretical aspects and studies of possible experimental signatures at the LHC and other colliders., Report of the CPNSH workshop, May 2004 - Dec 2005, 542 pages. The complete report as well as its individual chapters are also available from http://kraml.home.cern.ch/kraml/cpnsh/report.html

The Proceedings of the 2003 SLAC Workshops on flavor physics with a high luminosity asymmetric e+e- collider. The sensitivity of flavor physics to physics beyond the Standard Model is addressed in detail, in the context of the improvement of experimental measurements and theoretical calculations., Comment: 476 pages. Printed copies may be obtained by request to kwebb@slac.stanford.edu . arXiv admin note: v2 appears to be identical to v1

We examine the signatures for noncommutative QED at $e^+e^-$ colliders with center of mass energies in excess of 1 TeV such as CLIC. For integrated luminosities of 1 ab$^{-1}$ or more, sensitivities to the associated mass scales greater than $\sqrt s$ are possible., 4 pages, 4 figs, LaTex; Contributed to Snowmass 2001 Summer Study

We examine how mixing between the Standard Model(SM) Higgs boson, $h$, and the radion of the Randall-Sundrum model modifies the expected properties of the Higgs boson. In particular, we demonstrate that the total and partial decay widths of the Higgs, as well as the $h\to gg$ branching fraction, can be substantially altered from their SM expectations, while the remaining Higgs branching fractions are modified less than $\lsim 5%$ for most of the parameter region., 3 pgs, Contributed to the APS/DPF/DPB Summer Study on the Future of Particle Physics (Snowmass 2001), Snowmass, Colorado, 30 Jun - 21 Jul 2001

We begin to analyze and contrast the predictions for the decay $b\to s\ell^+\ell^-$ in the Left-Right Symmetric Model(LRM) with those of the Standard Model(SM). In particular, we show that the forward-backward asymmetry of the lepton spectrum can be used to distinguish the SM from the simplest manifestation of the LRM. [To appear in the Proceedings of the 2nd International Conference on B Physics and CP Violation, Honolulu, HI, 24-27 March 1997], Comment: 6 pages, 2 figures

We analyze the manifestations of new matter particles predicted by models of new physics beyond the Standard Model, at present and future high--energy colliders. We consider both the production of these new particles and some of their indirect signatures at $pp$ and $eP$ colliders as well as TeV $\ee$ colliders with their $\ee, e \gamma, \gamma \gamma$ and $e^- e^-$ modes. The report is arranged into four main sections plus an overview. These sections will deal separately with exotic and excited fermions, difermions, and new interactions., Comment: 64 pages, latex, 30 figures (not included). The full *.ps file including the figures can be obtained via anonymous ftp at ftp://lpsvsh.lps.umontreal.ca/hep_th/dpf.ps . To appear as a chapter in "Electroweak Symmetry Breaking and Beyond the Standard Model", edited by T. Barklow, S. Dawson, H.E. Haber and S. Siegrist, World Scientific

We explore the sensitivity of the on-going Tevatron search for charged, right-handed gauge bosons, $W_R^{\pm}$, to various model dependent assumptions such as the magnitude of the $SU(2)_R$ gauge coupling, the values of the right-handed Kobayashi-Maskawa mixing matrix elements, $(V_R)_{ij}$, and the nature of the right-handed neutrino. These results also have important implications for HERA searches for right-handed currents., LaTex, 13 pages, 11 figures (not included), ANL-HEP-PR-93-87

The NLC may allow us to search for the `inverse' process to neutrinoless double-$\beta$ decay, $e^-e^-\to W^-W^-$, which probes the existence of Majorana masses for neutrinos. Expectations for the observation of this process in both the Standard Model and its extension, the Left-Right Symmetric Model, are examined. (Talk given at the {\it {Workshop on Physics and Experiments at Linear $e^+e^-$ Colliders}}, Waikoloa, Hawaii.), Comment: 5 pages, 5 figures(not included), LaTex format with worldsci macro, ANL-HEP-CP-93-24

Possible anomalous couplings of the top-quark to on-shell photons and gluons are constrained by the recent results of the CLEO Collaboration on both inclusive and exclusive radiative $B$ decays. We find that the process \bsg\ can lead to reasonable bounds on both the anomalous electric and magnetic dipole moments of the top-quark, while essentially no limits are obtained on the corresponding chromoelectric and chromomagnetic moments, which enter the expression for the decay rate only through operator mixing., Comment: 10 pages plus 6 figures (available by request), LaTex, ANL-HEP-PR-93-37

The recent results of the CLEO Collaboration on both inclusive and exclusive radiative $B$ decays are combined with those of the UA2 Collaboration on $W\gamma$ production to highly constrain the anomalous trilinear gauge couplings of the $W$. The theoretical analysis of the $b \to s\gamma$ process employs, next-to-leading order operator coefficient evolution as well as QCD bremsstrahlung and appropriate phase space corrections., Comment: 10 pages, 6 figures(not included), LaTex, ANL-HEP-PR-93-19

The NLC may allow us to search for the `inverse' process to neutrinoless double-$��$ decay, $e^-e^-\to W^-W^-$, which probes the existence of Majorana masses for neutrinos. Expectations for the observation of this process in both the Standard Model and its extension, the Left-Right Symmetric Model, are examined. (Talk given at the {\it {Workshop on Physics and Experiments at Linear $e^+e^-$ Colliders}}, Waikoloa, Hawaii.), 5 pages, 5 figures(not included), LaTex format with worldsci macro, ANL-HEP-CP-93-24

Possible anomalous couplings of the top-quark to on-shell photons and gluons are constrained by the recent results of the CLEO Collaboration on both inclusive and exclusive radiative $B$ decays. We find that the process \bsg\ can lead to reasonable bounds on both the anomalous electric and magnetic dipole moments of the top-quark, while essentially no limits are obtained on the corresponding chromoelectric and chromomagnetic moments, which enter the expression for the decay rate only through operator mixing., 10 pages plus 6 figures (available by request), LaTex, ANL-HEP-PR-93-37

The recent results of the CLEO Collaboration on both inclusive and exclusive radiative $B$ decays are combined with those of the UA2 Collaboration on $W��$ production to highly constrain the anomalous trilinear gauge couplings of the $W$. The theoretical analysis of the $b \to s��$ process employs, next-to-leading order operator coefficient evolution as well as QCD bremsstrahlung and appropriate phase space corrections., 10 pages, 6 figures(not included), LaTex, ANL-HEP-PR-93-19

The possibility that the interactions of the third generation of quarks and leptons may violate universality by a small amount remains an open experimental question. The model of Li and Ma, which naturally accommodates such violations, is found to be highly constrained by newly obtained, high precision electroweak and $\tau$-lepton data once full Standard Model radiative corrections are incorporated into the analysis. A comparison of the predictions of this model with existing data and the expectations for future colliders is presented., Comment: 14 pages, 13 figures, available on request, LaTex, ANL-HEP-PR-93-20

We summarize the results of the extended gauge group working group of the Madison-Argonne Workshop on Present and Future Colliders. Contributions are described on the previously unexamined two photon fusion production of heavy leptons, new studies of $Z'$ couplings to $\nu \bar{\nu}$ and $q\bar{q}$, and previously unexplored vector leptoquark production. More detailed accounts of these studies can be found in individual contributions., Comment: (at the Argonne-Madison Workshop on Physics at Current Accelerators and the Supercollider), 6 pages, latex with epsfig and worldsci. The postcript file is available via anonymous ftp at hepcu.physics.carleton.ca as disk$userd:[peterson.tex]ocipc9311.ps ANL-HEP-CP-93-60, OCIP/C-93-11

We point out that in a class of supersymmetric models where R-parity violation is induced by the spontaneous breaking of local $B-L$ symmetry, the R-parity violating $W$ decay $W\rightarrow\slep\gamma$ and $Z$ decay $Z\rightarrow\snu\gamma$, forbidden in the minimal supersymmetric standard model (MSSM), occur at an enhanced rate compared to other models with R-parity breaking. We find that the branching fractions for these modes can be of order $10^{-5}$ ., Comment: 15 pages, 4 figures(available upon request), LaTex, UMD-PP-93-90

Models with explicit R-parity violation can induce new rare radiative decay modes of the $W$ boson into single supersymmetric particles which also violate lepton number. We examine the rate and signature for one such decay, $W\rightarrow \tilde l\gamma$, and find that such a mode will be very difficult to observe, due its small branching fraction, even if the lepton number violating coupling in the superpotential is comparable in strength to electromagnetism. This parallels a similar result obtained earlier by Hewett in the case of radiative $Z$ decays., Comment: 10 pages, 2 figures(available on request), LaTex, ANL-HEP-PR-92-81

We examine how the abilities of an SDC-like detector to discover and identify the origin of a new neutral gauge boson are affected by $Z_1-Z_2 $ mixing and by variations in detector parameters such as lepton pair mass resolution, particle identification efficiency, and rapidity coverage. Also examined is the sensitivity of these results to variations in structure function uncertainties and uncertainties in the machine integrated luminosity. Such considerations are of importance when dealing with the issues of detector descoping and design., Comment: 17 pages, 4 figures (available by request), phyzzx, ANL-HEP-PR-92-34

Doncheski and Hewett have recently shown that the ratio of neutral current to charged current cross sections, $R={\sigma_{NC}}/{\sigma_{CC}}$, can provide a more sensitive probe for the existence of heavy leptoquarks at HERA than the usual proceedure which makes use of neutral current asymmetries. The apparent reason for this is that the Standard Model expectations for {\it both} of these cross sections are modified by the existence of such particles in a semi-coherent manner. In this paper we apply this technique to extended electroweak models whose spectrum contains both a $W'$ and a $Z'$. We find that measurements of $R$ can, for some models, substantially increase the HERA search range for new gauge bosons beyond that which can be probed using the more conventional asymmetries., Comment: LaTex format, 21 pages, 8 figures(not included), ANL-HEP-PR-92-37

Letter of intent describing SiD (Silicon Detector) for consideration by the International Linear Collider IDAG panel. This detector concept is founded on the use of silicon detectors for vertexing, tracking, and electromagnetic calorimetry. The detector has been cost-optimized as a general-purpose detector for a 500 GeV electron-positron linear collider., Comment: Letter of Intent for SiD detector concept presented to ILC IDAG