Linda M. Carpenter

Linda M. Carpenter
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Linda M. Carpenter

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High Energy Physics - Phenomenology (32)
High Energy Physics - Experiment (7)
High Energy Physics - Theory (4)
High Energy Astrophysical Phenomena (2)

Publications Authored By Linda M. Carpenter

I explore the phenomenology of Supersymmetry models in which the gauginos are much heavier then that scalar particles of the MSSM. In these models, the gauginos are inaccessible to colliders while the scalar spectrum is compressed. I give several examples of models which exhibit this phenomenology built in the class of General Gauge Mediated Models. Read More

We study the Higgs boson $(h)$ decay to two light jets at the 14 TeV High-Luminosity-LHC (HL-LHC), where a light jet ($j$) represents any non-flavor tagged jet from the observational point of view. The decay mode $h\to gg$ is chosen as the benchmark since it is the dominant channel in the Standard Model (SM), but the bound obtained is also applicable to the light quarks $(j=u,d,s)$. We estimate the achievable bounds on the decay branching fractions through the associated production $Vh\ (V=W^\pm,Z)$. Read More

Recent Fermi-LAT observations of dwarf spheroidal galaxies in the Milky Way have placed strong limits on the gamma-ray flux from dark matter annihilation. In order to produce the strongest limit on the dark matter annihilation cross-section, the observations of each dwarf galaxy have typically been "stacked" in a joint-likelihood analysis, utilizing optical observations to constrain the dark matter density profile in each dwarf. These limits have typically been computed only for singular annihilation final states, such as $b\bar{b}$ or $\tau^+\tau^-$. Read More

We propose that the sbino, the scalar partner of a Dirac bino can explain the 750 GeV diphoton excess observed by ATLAS and CMS . We analyze a model in which the sbino couples to pairs of Standard Model (SM) gauge bosons. We analyze an effective operator model, as well as a completion in which the sbino couples to pairs of gauge bosons through loops of heavy sfermions. Read More

We explore the phenomenology of scalar fields in the adjoint representation of SM gauge groups. We write a general set of dimension 5 effective operators in which SM adjoint scalars couple to pairs of standard model bosons. Using these effective operators, we explore new possible decay channels of a scalar color octet into a gluon and a Z boson/ gluon and a photon. Read More

Authors: Daniel Abercrombie, Nural Akchurin, Ece Akilli, Juan Alcaraz Maestre, Brandon Allen, Barbara Alvarez Gonzalez, Jeremy Andrea, Alexandre Arbey, Georges Azuelos, Patrizia Azzi, Mihailo Backović, Yang Bai, Swagato Banerjee, James Beacham, Alexander Belyaev, Antonio Boveia, Amelia Jean Brennan, Oliver Buchmueller, Matthew R. Buckley, Giorgio Busoni, Michael Buttignol, Giacomo Cacciapaglia, Regina Caputo, Linda Carpenter, Nuno Filipe Castro, Guillelmo Gomez Ceballos, Yangyang Cheng, John Paul Chou, Arely Cortes Gonzalez, Chris Cowden, Francesco D'Eramo, Annapaola De Cosa, Michele De Gruttola, Albert De Roeck, Andrea De Simone, Aldo Deandrea, Zeynep Demiragli, Anthony DiFranzo, Caterina Doglioni, Tristan du Pree, Robin Erbacher, Johannes Erdmann, Cora Fischer, Henning Flaecher, Patrick J. Fox, Benjamin Fuks, Marie-Helene Genest, Bhawna Gomber, Andreas Goudelis, Johanna Gramling, John Gunion, Kristian Hahn, Ulrich Haisch, Roni Harnik, Philip C. Harris, Kerstin Hoepfner, Siew Yan Hoh, Dylan George Hsu, Shih-Chieh Hsu, Yutaro Iiyama, Valerio Ippolito, Thomas Jacques, Xiangyang Ju, Felix Kahlhoefer, Alexis Kalogeropoulos, Laser Seymour Kaplan, Lashkar Kashif, Valentin V. Khoze, Raman Khurana, Khristian Kotov, Dmytro Kovalskyi, Suchita Kulkarni, Shuichi Kunori, Viktor Kutzner, Hyun Min Lee, Sung-Won Lee, Seng Pei Liew, Tongyan Lin, Steven Lowette, Romain Madar, Sarah Malik, Fabio Maltoni, Mario Martinez Perez, Olivier Mattelaer, Kentarou Mawatari, Christopher McCabe, Théo Megy, Enrico Morgante, Stephen Mrenna, Siddharth M. Narayanan, Andy Nelson, Sérgio F. Novaes, Klaas Ole Padeken, Priscilla Pani, Michele Papucci, Manfred Paulini, Christoph Paus, Jacopo Pazzini, Björn Penning, Michael E. Peskin, Deborah Pinna, Massimiliano Procura, Shamona F. Qazi, Davide Racco, Emanuele Re, Antonio Riotto, Thomas G. Rizzo, Rainer Roehrig, David Salek, Arturo Sanchez Pineda, Subir Sarkar, Alexander Schmidt, Steven Randolph Schramm, William Shepherd, Gurpreet Singh, Livia Soffi, Norraphat Srimanobhas, Kevin Sung, Tim M. P. Tait, Timothee Theveneaux-Pelzer, Marc Thomas, Mia Tosi, Daniele Trocino, Sonaina Undleeb, Alessandro Vichi, Fuquan Wang, Lian-Tao Wang, Ren-Jie Wang, Nikola Whallon, Steven Worm, Mengqing Wu, Sau Lan Wu, Hongtao Yang, Yong Yang, Shin-Shan Yu, Bryan Zaldivar, Marco Zanetti, Zhiqing Zhang, Alberto Zucchetta

This document is the final report of the ATLAS-CMS Dark Matter Forum, a forum organized by the ATLAS and CMS collaborations with the participation of experts on theories of Dark Matter, to select a minimal basis set of dark matter simplified models that should support the design of the early LHC Run-2 searches. A prioritized, compact set of benchmark models is proposed, accompanied by studies of the parameter space of these models and a repository of generator implementations. This report also addresses how to apply the Effective Field Theory formalism for collider searches and present the results of such interpretations. Read More

Using limits on photon flux from Dwarf Spheroidal galaxies, we place bounds on the parameter space of models in which Dark Matter annihilates into multiple final state particle pair channels. We derive constraints on effective operator models with Dark Matter couplings to third generation fermions and to pairs of Standard Model vector bosons. We present limits in various slices of model parameter space along with estimations of the region of maximal validity of the effective operator approach for indirect detection. Read More

In this work we calculate important one loop SUSY-breaking parameters in models with Dirac gauginos, which are implied by the existence of heavy messenger fields. We find that these SUSY-breaking effects are all related by a small number of parameters, thus the general theory is tightly predictive. In order to make the most accurate analyses of one loop effects, we introduce calculations using an expansion in SUSY breaking messenger mass, rather than relying on postulating the forms of effective operators. Read More

In this paper we discuss search strategies at the LHC for light electroweak gauginos which are mostly Wino-like, Higgsino-like or an admixture. These states are typically degenerate with decay products that are less energetic and hence difficult to detect. In addition, their production cross-sections at a hadron collider are suppressed compared to colored states such as the gluinos. Read More

In this paper we present a novel formulation of chaotic hybrid inflation in supergravity. The model includes a waterfall field which spontaneously breaks a gauged $U_1(B-L)$ at a GUT scale. This allows for the possibility of future model building which includes the standard formulation of baryogenesis via leptogenesis with the waterfall field decaying into right-handed neutrinos. Read More

We describe an effective theory of interaction between pairs of dark matter particles (denoted $\chi$) and pairs of $W$ bosons. Such an interaction could accommodate $\chi\bar{\chi}\rightarrow WW$ processes, which are a major focus of indirect dark matter experiments, as well as $pp \rightarrow W\rightarrow W\chi\bar{\chi}$ processes, which would predict excesses at the LHC in the $W$+MET final-state. We reinterpret an ATLAS $W$+MET analysis in the hadronic mode and translate the bounds to the space of indirect detection signals. Read More

We explore the LHC phenomenology of dark matter (DM) pair production in association with a 125 GeV Higgs boson. This signature, dubbed `mono-Higgs,' appears as a single Higgs boson plus missing energy from DM particles escaping the detector. We perform an LHC background study for mono-Higgs signals at $\sqrt{s} = 8$ and $14$ TeV for four Higgs boson decay channels: $\gamma\gamma$, $b \bar b$, and $ZZ^* \to 4\ell$, $\ell\ell j j$. Read More

We describe an effective theory of interaction between pairs of dark matter particles and pairs of photons. Such an interaction could accomodate $\chi\bar{\chi}\rightarrow\gamma\gamma$ processes which might be the cause of the observed feature in the FermiLAT spectrum, as well as $\gamma^*/Z\rightarrow \gamma\chi\bar{\chi}$ processes, which would predict excesses at the LHC in the $\gamma+\missET$ final-state. We reinterpret an ATLAS $\gamma+\missET$ analysis and the observed Fermi feature in the parameter space of our new effective theory to assess their consistency. Read More

Searches for dark matter at colliders typically involve signatures with energetic initial-state radiation without visible recoil particles. Searches for mono-jet or mono-photon signatures have yielded powerful constraints on dark matter interactions with Standard Model particles. We extend this to the mono-Z signature and reinterpret an ATLAS analysis of events with a Z boson and missing transverse momentum to derive constraints on dark matter interaction mass scale and nucleon cross sections in the context of effective field theories describing dark matter which interacts via heavy mediator particles with quarks or weak bosons. Read More

We consider general fermi-phobic scenarios in which excess events in diphoton or WW/ZZ resonances may be seen at LHC. These Higgs like signals do not necessarily suggest that the new resonance is a particle with Yukawa couplings nor do we know that it is responsible for electroweak symmetry breaking. We can, however, extract two facts from it, this particle couples to pairs of SU(2) and U(1) gauge bosons and it must be a scalar, pseudoscalar, or tensor. Read More

I present a general exclusion bound for the Higgs in fourth generation scenarios with a general lepton sector. Recent Higgs searches in fourth generation scenarios rule out the entire Higgs mass region between 120 and 600 GeV. That such a large range of Higgs masses are excluded is due to the presence of extra heavy flavors of quarks, which substantially increase Higgs production from gluon fusion over the Standard Model rate. Read More

We study the pair production of fourth generation neutrinos from the decay of an on-shell Higgs produced by gluon fusion. In a fourth generation scenario, the Higgs branching fraction into fourth generation neutrinos may be quite large. In the case that the unstable heavy neutrinos are a mixed Majorana and Dirac state, neutrinos pair-produced from Higgs decay will yield a substantial number of like-sign dilepton events. Read More

We study the phenomenology of color-octet scalars in the (8, 2)1/2 representation in the context of the 3.2\sigma excess, in the dijet invariant mass spectrum of the W+jj final state, recently observed by the CDF collaboration. We consider the region of parameter space with a sizable mass splitting between the charged and neutral color-octet scalars and consistent with electroweak precision data. Read More

I analyze a fourth generation lepton sector in which the lightest particle is a stable Majorana neutrino. In this scenario fourth generation neutrinos have both a Dirac and Majorana mass, resulting in two Majorana neutrino mass eigenstates. A reanalysis of LEP's lower mass bound is performed on stable Majorana neutrinos from the Z width and the lower mass bound is loosened. Read More

We study the production and decay of fourth generation leptons at the Large Hadron Collider (LHC).We find that for charged leptons with masses under a few hundred GeV, the dominant collider signal comes from the production through a W-boson of a charged and neutral fourth generation lepton. We present a sensitivity study for this process in events with two like-sign charged leptons and at least two associated jets. Read More

In an attempt to maximize General Gauge Mediated parameter space, I propose simple models in which gauginos and scalars are generated from disconnected mechanisms. In my models Dirac gauginos are generated through the supersoft mechanism, while independent R-symmetric scalar masses are generated through operators involving non-zero messenger supertrace. I propose several new methods for generating negative messenger supertraces which result in viable positive mass squareds for MSSM scalars. Read More

We revisit the current experimental bounds on fourth-generation Majorana neutrino masses, including the effects of right handed neutrinos. Current bounds from LEPII are significantly altered by a global analysis. We show that the current bounds on fourth generation neutrinos decaying to eW and mu W can be reduced to about 80 GeV (from the current bound of 90 GeV), while a neutrino decaying to tau W can be as light as 62. Read More

In supersymmetric theories, the presence of axions usually implies the existence of a non-compact, (pseudo)moduli space. In gauge mediated models, the axion would seem a particularly promising dark matter candidate. The cosmology of the moduli then constrains the gravitino mass and the axion decay constant; the former can't be much below 10 MeV; the latter can't be much larger than 10^{13} GeV. Read More

Invoking the Peccei-Quinn (PQ) solution to the strong CP problem substitutes the puzzle of why $\theta_{qcd}$ is so small with the puzzle of why the PQ symmetry is of such high quality. Cosmological and astrophysical considerations raise further puzzles. This paper explores this issues in several contexts: string theory and field theory, and theories without and with low energy supersymmetry. Read More

I explore the phenomenology, constraints and tuning for several weakly coupled implementations of multi-parameter gauge mediation and compare to minimal gauge mediation. The low energy spectra are distinct from that of minimal gauge mediation, a wide range of NLSPs is found and spectra are significantly compressed thus tunings may be generically reduced to a part in 10 to a part in 20. Read More

I propose implementing General Gauge Mediation using the class of $SU(N) \times U(1)$ SUSY breaking models. As an existence proof, I have utilized the 4-1 model in building multi-parameter gauge mediation. These hidden sectors are relatively easy to use and avoid several model building pitfalls such as runaway directions. Read More

Recently there has been much progress in building models of gauge mediation, often with predictions different than those of minimal gauge mediation. Meade, Seiberg, and Shih have characterized the most general spectrum which can arise in gauge mediated models. We discuss some of the challenges of building models of General Gauge Mediation, especially the problem of messenger parity and issues connected with R symmetry breaking and CP violation. Read More

We discuss SUSY models in which renormalizable lepton number violating couplings hide the decay of the Higgs through h -> \chi_1^0 + \chi_1^0 followed by \chi_1^0 -> \tau + 2 jets or \chi_1^0 -> \nu_\tau + 2 jets and also explain neutrino masses. This mechanism can be made compatible with gauge mediated SUSY breaking. Read More

In supersymmetric models with R parity violation, constraints on superpartner masses are significantly weaker than in models which conserve R parity. We find in regions of parameter space where a neutral gaugino or third generation scalar is decoupled from the Z and/or traditional gaugino mass relationships do not hold allow some particles to be light enough to allow them to be the decay products of the Higgs. For example, surprisingly a stau could be lighter than 30 GeV if it decays hadronically. Read More

Both electroweak precision measurements and simple supersymmetric extensions of the standard model prefer a mass of the Higgs boson less than the experimental lower limit of 114 GeV. We show that supersymmetric models with R parity violation and baryon number violation have a significant range of parameter space in which the Higgs dominantly decays to six jets. These decays are much more weakly constrained by current LEP analyses and would allow for a Higgs mass near that of the $Z$. Read More

I provide a minimal method for generating a mu term and positive slepton masses within the framework of anomaly mediation. I introduce a new operator involving a hidden sector U(1) gauge field which is then canceled against a Giudice-Masiero-like mu term. No new flavor violating operators are allowed. Read More

We introduce a new model of supersymmetry breaking dominated by anomaly mediation. It has a viable spectrum, successful electroweak symmetry breaking, solves the mu-problem and maintains the anomaly-mediated form for soft-masses down to low energies thus solving the flavor problem. The model consists of the minimal supersymmetric standard model plus a singlet, anomaly-mediated soft masses and a dirac mass which marries the bino to the singlet. Read More