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Daniel Whiteson

Publications and source records attributed to Daniel Whiteson.

At least 91 records · Page 5Linked to original sources
arXiv2014

Systematically Searching for New Resonances at the Energy Frontier using Topological Models

We propose a new strategy to systematically search for new physics processes in particle collisions at the energy frontier. An examination of all possible topologies which give identifiable resonant features in a specific final state leads to a tractable number of `topological models' per final state and gives specific guidance for their discovery. Using one specific final state, $\ell\ell jj$, as an example, we find that the number of possibilities is reasonable and reveals simple, but as-yet-unexplored, topologies which contain significant discovery potential. We propose analysis techniques and estimate the sensitivity for $pp$ collisions with $\sqrt{s}=14$ TeV and $\mathcal{L}=300$ fb$^{-1}$.

hep-ph↗
arXiv2013

Warped Extra Dimensional Benchmarks for Snowmass 2013

The framework of a warped extra dimension with the Standard Model (SM) fields propagating in it is a very well-motivated extension of the SM since it can address both the Planck-weak and flavor hierarchy problems of the SM. We consider signals at the 14 and 33 TeV large hadron collider (LHC) resulting from the direct production of the new particles in this framework, i.e.,Kaluza-Klein (KK) excitations of the SM particles. We focus on spin-1 (gauge boson) and spin-2 (graviton) KK particles and their decays to top/bottom quarks (flavor-conserving) and W/Z and Higgs bosons, in particular. We propose two benchmarks for this purpose, with the right-handed (RH) or LH top quark, respectively, being localized very close to the TeV end of the extra dimension. We present some new results at the 14 TeV (with 300 fb$^-1$ and 3000 fb$^-1$) and 33 TeV LHC. We find that the prospects for discovery of these particles are quite promising, especially at the high-luminosity upgrade.

hep-ph↗
arXiv2013

Confronting the Fermi Line with LHC data: an Effective Theory of Dark Matter Interaction with Photons

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

hep-ph↗
arXiv2013

Mono-everything: combined limits on dark matter production at colliders from multiple final states

Searches for dark matter production at particle colliders are complementary to direct-detection and indirect-detection experiments, and especially powerful for small masses, $m_χ<100$ GeV. An important collider dark matter signature is due to the production of a pair of these invisible particles with the initial-state radiation of a standard model particle. Currently, collider searches use individual and nearly orthogonal final states to search for initial-state jets, photons or massive gauge bosons. We combine these results across final states and across experiments to give the strongest current collider-based limits in the context of effective field theories, and map these to limits on dark matter interactions with nuclei and to dark matter self-annhiliation.

hep-ex↗
arXiv2013

Searching for Spurious Solar and Sky Lines in the Fermi-LAT Spectrum

We search for a unified instrumental explanation of the spectral features seen near $E_γ=130$ GeV in photons collected by Fermi-LAT from the galactic center and from the Earth's limb. We report for the first time a similar feature in photons originating from the vicinity of the Sun, and examine the instrumental characteristics of this Solar feature. To test an instrumental hypothesis, we identify the range of photon incident angles where most of the peak photons are observed in these three spectral features. An examination of the spectrum of photons from the rest of the sky with this characteristic angular range reveals a hint of a spectral feature near $E_γ=130$ GeV. These results cast further doubt on the dark-matter-annihilation interpretation of the galactic center peak.

astro-ph.HE↗
arXiv2012

Collider searches for dark matter in events with a Z boson and missing energy

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.

hep-ex↗
arXiv2012

Where are the Fermi Lines Coming From?

We estimate the spatial locations of sources of the the observed features in the Fermi-LAT photon spectrum at $E_γ=110$ and $E_γ=130$ GeV. We determine whether they are consistent with emission from a single source, as would be expected in their interpretation as $γγ$ and $γZ$ lines from dark matter annhiliation, as well as whether they are consistent with a dark matter halo positioned at the center of the galaxy. We take advantage of the per-photon measured incident angle in reconstructing the line features. In addition, we use a data-driven background model rather than making the assumption of a feature-less background. We localize the sources of the features at 110 and 130 GeV. Assuming an Einasto (NFW) density model we find the 130 GeV line to be offset from the galactic center by 285 (280) pc, the 110 GeV line by 60 (30) pc with a large relative separation of 220 (240) pc. However, we find this displacement of each source from the galactic center, as well as their relative displacement to be statistically consistent with a single Einasto or NFW dark matter halo at the center of the galaxy.

astro-ph.HE↗
arXiv2012

Disentangling Instrumental Features of the 130 GeV Fermi Line

We study the instrumental features of photons from the peak observed at $E_γ=130$ GeV in the spectrum of Fermi-LAT data. We use the {\sc sPlots} algorithm to reconstruct -- seperately for the photons in the peak and for background photons -- the distributions of incident angles, the recorded time, features of the spacecraft position, the zenith angles, the conversion type and details of the energy and direction reconstruction. The presence of a striking feature or cluster in such a variable would suggest an instrumental cause for the peak. In the publically available data, we find several suggestive features which may inform further studies by instrumental experts, though the size of the signal sample is too small to draw statistically significant conclusions.

astro-ph.HE↗
arXiv2012

Reinterpretion of Experimental Results with Basis Templates

Experimental analysis of data from particle collisions is typically expressed as statistical limits on a few benchmark models of particular, often historical, interest. The implications of the data for other theoretical models (current or future) may be powerful, but they cannot typically be calculated from the published information, except in the simplest case of a single-bin counting experiment. We present a novel solution to this long-standing problem by expressing the new model as a linear combination of models from published experimental analysis, allowing for the trivial calculation of limits on a nearly arbitrary model. We present tests in simple toy experiments, demonstrate self-consistency by using published results to reproduce other published results on the same spectrum, and provide a reinterpretation of a search for chiral down-type heavy quarks ($b'$) in terms of a search for an exotic heavy quark ($T$) with similar but distinct phenomenology. We find $m_T>419$ GeV at 95% CL, currently the strongest limits if the $T$ quark decays via $T\rightarrow Wb, T\rightarrow tZ$ and $T\rightarrow tH$.

hep-ex↗
arXiv2012

Two Lines or Not Two Lines? That is the Question of Gamma Ray Spectra

Lines in the spectrum of cosmic gamma rays are considered one of the more robust signatures of dark matter annihilation. We consider such processes from an effective field theory vantage, and find that generically, two or more lines are expected, providing an interesting feature that can be exploited for searches and reveal details about the underlying theory of dark matter. Using the 130 GeV feature recently reported in the Fermi-LAT data as an example, we analyze the energy spectrum in the multi-line context and find the data to be consistent with a single $γγ$ line, a single $γZ$ line or both a $γγ$ and a $γZ$ line.

hep-ph↗
arXiv2012

Triangulating an exotic T quark

Limits on an exotic heavy quark $T$ are broadly generalized by considering the full range of $T\rightarrow Wb, th$ or $tZ$ branching ratios. We combine results of specific $T\rightarrow tZ$ and $T\rightarrow Wb$ searches with limits on various combinations of decay modes evaluated by re-interpreting other searches. We find strong bounds across the entire space of branching ratios, ranging from $m_T > 415$ GeV to $m_T > 557$ GeV at 95% confidence level.

hep-ph↗
arXiv2012

Limits on Four-Top Production from the ATLAS Same-sign Top-quark Search

We repurpose the recent ATLAS search for same-sign top quarks in data with 1.0 fb$^{-1}$ in the context of a search for production of four top quarks. Using the null results of that search, we place limits on the four-top-quark production cross section of about 1 pb. These limits are larger than the expected Standard Model rate for four-top-quark production, but are already strong enough to place interesting constraints on models which enhance that rate. We interpret these results in the context of models in which the right-handed top quark is composite and find limits on the compositeness scale of about 700 GeV.

hep-ph↗
arXiv2012

Searching for $Z'$ bosons decaying to gluons

The production and decay of a new heavy vector boson, a chromophilic $Z'$ vector boson, is described. The chromophilic $Z'$ couples only to two gluons, but its two-body decays are absent, leading to a dominant decay mode of $Z'\rightarrow q\bar{q}g$. The unusual nature of the interaction predicts a cross-section which grows with $m_{Z'}$ for a fixed coupling and an accompanying gluon with a coupling that rises with its energy. We study the $t\bar{t}g$ decay mode, proposing distinct reconstruction techniques for the observation of an excess and for the measurement of $m_{Z'}$. We estimate the sensitivity of current experimental datasets.

hep-ph↗
arXiv2011

Search for new phenomena in events with two $Z$ bosons and missing transverse momentum in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV

We present a search for new phenomena in events with two reconstructed $Z$ bosons and large missing transverse momentum, sensitive to processes $p\bar{p}\rightarrow X_2X_2 \rightarrow Z Z X_1 X_1$, where $X_2$ is an unstable particle decaying as $X_2\rightarrow ZX_1$ and $X_1$ is undetected. The particles $X_1$ and $X_2$ may be, among other possibilities, fourth generation neutrinos or supersymmetric particles. We study the final state in which one $Z$ boson decays to two charged leptons and the second decays hadronically. In data corresponding to an integrated luminosity of 4.2 fb$^{-1}$ from proton-antiproton collisions recorded by the CDF II detector at the Tevatron, with center-of-mass energy of 1.96 TeV, we find agreement between data and standard-model backgrounds. We calculate 95% confidence level upper limits on the cross section of the process $p\bar{p}\rightarrow X_2X_2 \rightarrow Z Z X_1 X_1$ ranging from 50 fb to 1 pb, depending on the masses of $X_1$ and $X_2$.

hep-ex↗
arXiv2011

Higgs Decays to Unstable Neutrinos: Collider Constraints from Inclusive Like-Sign Dilepton Searches

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. In this article we use inclusive like-sign dilepton searches from hadron colliders to constrain the theoretical parameter space of fourth generation leptons.

hep-ph↗
arXiv2011

Fourth generation quark mass limits in CKM-element space

We present a reanalysis of CDF data to extend limits on individual fourth-generation quark masses from particular flavor-mixing rates to the entire space of possible mixing values. Measurements from CDF have set individual limits on masses, $m_{b'}$ and $m_{t'}$, at the level of $335$--$385$ GeV assuming specific and favorable flavor-mixing rates. We consider the space of possible values for the mixing rates and find that the CDF data imply limits of $290$ GeV and greater over a wide range of mixing scenarios. We also analyze the limits from the perspective of a four-generation CKM matrix. We find that present experimental constraints on CKM elements do not suggest further constraints on fourth-generation quark masses.

hep-ph↗