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Daniel Stolarski

Publications and source records attributed to Daniel Stolarski.

At least 55 records · Page 3Linked to original sources
arXiv2016

The Virtual Diphoton Excess

Interpreting the excesses around 750 GeV in the diphoton spectra to be the signal of a new heavy scalar decaying to photons, we point out the possibility of looking for correlated signals with virtual photons. In particular, we emphasize that the effective operator that generates the diphoton decay will also generate decays to two leptons and a photon, as well as to four leptons, independently of the new resonance couplings to $Zγ$ and $ZZ$. Depending on the relative sizes of these effective couplings, we show that the virtual diphoton component can make up a sizable, and sometimes dominant, contribution to the total $2\ell γ$ and $4\ell$ partial widths. We also discuss modifications to current experimental cuts in order to maximize the sensitivity to these virtual photon effects. Finally, we briefly comment on prospects for channels involving other Standard Model fermions as well as more exotic decay possibilities of the putative resonance.

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arXiv2015

Golden Probe of the Top Yukawa

We describe how the Higgs decay to four leptons can be used to probe the nature and $CP$ structure of the top Yukawa coupling.

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arXiv2015

Putting a Stop to di-Higgs Modifications

Pair production of Higgs bosons at hadron colliders is an enticing channel to search for new physics. New colored particles that couple strongly to the Higgs, such as those most often called upon to address the hierarchy problem, provide well motivated examples in which large enhancements of the di-Higgs rate are possible, at least in principle. However, in such scenarios the di-Higgs production rate is tightly correlated with the single Higgs production rate and, since the latter is observed to be SM-like, one generally expects that only modest enhancements in di-Higgs production are allowed by the LHC Run 1 data. We examine the contribution of top squarks (stops) in a simplified supersymmetry model to di-Higgs production and find that this general expectation is indeed borne out. In particular, the allowed deviations are typically small, but there are tuned regions of parameter space where expectations based on EFT arguments break down in which order 100% enhancements to the di-Higgs production rate are possible and are simultaneously consistent with the observed single Higgs production rates. These effects are potentially observable with the high luminosity run of the LHC or at a future hadron collider.

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arXiv2015

Interactions of a Stabilized Radion and Duality

We determine the couplings of the graviscalar radion in Randall-Sundrum models to Standard Model fields propagating in the bulk of the space, taking into account effects arising from the dynamics of the Goldberger-Wise scalar that stabilizes the size of the extra dimension. The leading corrections to the radion couplings are shown to arise from direct contact interactions between the Goldberger-Wise scalar and the Standard Model fields. We obtain a detailed interpretation of the results in terms of the holographic dual of the radion, the dilaton. In doing so, we determine how the familiar identification of the parameters on the two sides of the AdS/CFT correspondence is modified in the presence of couplings of the bulk Standard Model fields to the Goldberger-Wise scalar. We find that corrections to the form of the dilaton couplings from effects associated with the stabilization of the extra dimension are suppressed by the square of the ratio of the dilaton mass to the Kaluza-Klein scale, in good agreement with results from the CFT side of the correspondence.

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arXiv2015

Emerging Jets

In this work, we propose a novel search strategy for new physics at the LHC that utilizes calorimeter jets that (i) are composed dominantly of displaced tracks and (ii) have many different vertices within the jet cone. Such emerging jet signatures are smoking guns for models with a composite dark sector where a parton shower in the dark sector is followed by displaced decays of dark pions back to SM jets. No current LHC searches are sensitive to this type of phenomenology. We perform a detailed simulation for a benchmark signal with two regular and two emerging jets, and present and implement strategies to suppress QCD backgrounds by up to six orders of magnitude. At the 14 TeV LHC, this signature can be probed with mediator masses as large as 1.5 TeV for a range of dark pion lifetimes, and the reach is increased further at the high-luminosity LHC. The emerging jet search is also sensitive to a broad class of long-lived phenomena, and we show this for a supersymmetric model with R-parity violation. Possibilities for discovery at LHCb are also discussed.

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arXiv2015

A facility to Search for Hidden Particles at the CERN SPS: the SHiP physics case

This paper describes the physics case for a new fixed target facility at CERN SPS. The SHiP (Search for Hidden Particles) experiment is intended to hunt for new physics in the largely unexplored domain of very weakly interacting particles with masses below the Fermi scale, inaccessible to the LHC experiments, and to study tau neutrino physics. The same proton beam setup can be used later to look for decays of tau-leptons with lepton flavour number non-conservation, $τ\to 3μ$ and to search for weakly-interacting sub-GeV dark matter candidates. We discuss the evidence for physics beyond the Standard Model and describe interactions between new particles and four different portals - scalars, vectors, fermions or axion-like particles. We discuss motivations for different models, manifesting themselves via these interactions, and how they can be probed with the SHiP experiment and present several case studies. The prospects to search for relatively light SUSY and composite particles at SHiP are also discussed. We demonstrate that the SHiP experiment has a unique potential to discover new physics and can directly probe a number of solutions of beyond the Standard Model puzzles, such as neutrino masses, baryon asymmetry of the Universe, dark matter, and inflation

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arXiv2014

Split SUSY Radiates Flavor

Radiative flavor models where the hierarchies of Standard Model (SM) fermion masses and mixings are explained via loop corrections are elegant ways to solve the SM flavor puzzle. Here we build such a model in the context of Mini-Split Supersymmetry (SUSY) where both flavor and SUSY breaking occur at a scale of 1000 TeV. This model is consistent with the observed Higgs mass, unification, and WIMP dark matter. The high scale allows large flavor mixing among the sfermions, which provides part of the mechanism for radiative flavor generation. In the deep UV, all flavors are treated democratically, but at the SUSY breaking scale, the third, second, and first generation Yukawa couplings are generated at tree level, one loop, and two loops, respectively. Save for one, all the dimensionless parameters in the theory are O(1), with the exception being a modest and technically natural tuning that explains both the smallness of the bottom Yukawa coupling and the largeness of the Cabibbo angle.

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arXiv2013

Dynamics of a Stabilized Radion and Duality

We construct the effective theory of the graviscalar radion in the Randall-Sundrum scenario, taking into account effects arising from the stabilization of the extra dimension through the Goldberger-Wise mechanism. We explore the conditions under which the radion can remain light, and determine the corrections to its couplings to Standard Model (SM) states when the effects of stabilization are taken into account. We show that in the theories of interest for electroweak symmetry breaking that have a holographic dual, the presence of a light radion in the spectrum is not a robust prediction of the framework, but is in fact associated with mild tuning. We find that corrections to the form of the radion couplings to Standard Model particles arising from effects associated with brane stabilization are suppressed by the square of the ratio of the radion mass to the Kaluza-Klein scale. These corrections are small in theories where the radion is light, and are generally subleading, except in the case of couplings to the SM gluons and photon, when they can sometimes dominate. The AdS/CFT correspondence relates the radion in Randall-Sundrum models to the dilaton in theories where a strongly coupled conformal symmetry is spontaneously broken. We show that the discrepancies in the literature between the results for the dilaton and the radion can be traced to the omission of self-interaction terms that would otherwise dominate the potential for the Goldberger-Wise scalar near the infrared brane. In the dual picture, this corresponds to neglecting the corrections to the scaling behavior of the operator that breaks conformal symmetry when it grows large. With the inclusion of these self-interaction terms, we find good agreement between the results on the two sides of the correspondence.

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arXiv2013

Reach in All Hadronic Stop Decays: A Snowmass White Paper

We study the discovery prospects for stops which decay to a top and a light neutralino. We consider fully hadronic decays of the tops and present an estimate for the reach at various future collider runs. Our results are summarized in Table 1.

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arXiv2013

Gauging the Way to MFV

We present a UV complete model with a gauged flavor symmetry which approximately realizes holomorphic Minimal Flavor Violation (MFV) in R-parity violating (RPV) supersymmetry. Previous work has shown that imposing MFV as an ansatz easily evades direct constraints and has interesting collider phenomenology. The model in this work spontaneously breaks the flavor symmetry and features the minimum "exotic" field content needed to cancel anomalies. The flavor gauge bosons exhibit an inverted hierarchy so that those associated with the third generation are the lightest. This allows low energy flavor constraints to be easily satisfied and leaves open the possibility of flavor gauge bosons accessible at the LHC. The usual MSSM RPV operators are all forbidden by the new gauge symmetry, but the model allows a purely "exotic" operator which violates both R-parity and baryon number. Since the exotic fields mix with MSSM-like right handed quarks, diagonalizing the full mass matrix after flavor-breaking transforms this operator into the trilinear baryon number violating operator UDD with flavor coefficients all suppressed by three powers of Yukawa couplings. There is a limit where this model realizes exact MFV; we compute corrections away from MFV, show that they are under theoretical control, and find that the model is viable in large regions of parameter space.

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arXiv2012

Directly Measuring the Tensor Structure of the Scalar Coupling to Gauge Bosons

Kinematic distributions in the decays of the newly discovered resonance to four leptons can provide a direct measurement of the tensor structure of the particle's couplings to gauge bosons. Even if the particle is shown to be a parity even scalar, measuring this tensor structure is a necessary step in determining if this particle is responsible for giving mass to the Z. We consider a Standard Model like coupling as well as coupling via a dimension five operator to either ZZ or Zγ. We show that using full kinematic information from each event allows discrimination between renormalizable and higher dimensional coupling to ZZ at the 95% confidence level with O(50) signal events, and coupling to Zγcan be distinguished with as few as 20 signal events. This shows that these measurements can be useful even with this year's LHC data.

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arXiv2012

New Measurements with Stopped Particles at the LHC

Metastable particles are common in many models of new physics at the TeV scale. If charged or colored, a reasonable fraction of all such particles produced at the LHC will stop in the detectors and give observable out of time decays. We demonstrate that significant information may be learned from such decays about the properties (e.g. charge or spin) of this particle and of any other particles to which it decays, for example a dark matter candidate. We discuss strategies for measuring the type of decay (two- vs three-body), the types of particles produced, and the angular distribution of the produced particles using the LHC detectors. We demonstrate that with O(10-100) observed decay events, not only can the properties of the new particles be measured but indeed even the Lorentz structure of the decay operator can be distinguished in the case of three-body decays. These measurements can not only reveal the correct model of new physics at the TeV scale, but also give information on physics giving rise to the decay at energy scales far above those the LHC can probe directly.

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arXiv2012

Searching for Direct Stop Production in Hadronic Top Data at the LHC

We argue that evidence can be uncovered for stops between 300-600 GeV in 5 fb^-1 of 7 TeV proton-proton collisions if they decay into top quarks and light neutral particles. We also show that with 20 fb^-1 of 8 TeV running, discovery or exclusion can be made in large regions of parameter space. Events with a fully hadronic top/anti-top pair and a pair of invisible decay products can be identified with the top-tagging of a fat jet, a single b-tag, a missing transverse energy cut, as well as other kinematic cuts to reduce backgrounds with real top quarks in them. Such cuts obliterate the background suggesting discovery can be made with a handful of events.

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arXiv2011

A Fat Higgs with a Magnetic Personality

We introduce a novel composite Higgs theory based on confining supersymmetric QCD. Supersymmetric duality plays a key role in this construction, with a "fat" Higgs boson emerging as a dual magnetic degree of freedom charged under the dual magnetic gauge group. Due to spontaneous color-flavor locking in the infrared, the electroweak gauge symmetry is aligned with the dual magnetic gauge group, allowing large Yukawa couplings between elementary matter fields and the composite Higgs. At the same time, this theory exhibits metastable supersymmetry breaking, leading to low-scale gauge mediation via composite messengers. The Higgs boson is heavier than in minimal supersymmetric theories, due to non-decoupling D-terms and a large F-term quartic coupling. This theory predicts quasi-stable TeV-scale pseudo-modulini, some of which are charged under standard model color, possibly giving rise to long-lived R-hadrons at the LHC.

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arXiv2010

The Bestest Little Higgs

While little Higgs models provide an interesting way to address the hierarchy problem, concrete models in the literature typically face two major obstacles. First, the mechanism for generating a Higgs quartic coupling often leads to large violations of custodial symmetry. Second, there is a tension between precision electroweak observables in the gauge sector and fine-tuning in the top sector. In this work, we present a new little Higgs model which solves both of these problems. The model is based on an SO(6)xSO(6)/SO(6) coset space which has custodial symmetry built in. The Higgs quartic coupling takes a particularly simple form and does not suffer from the "dangerous singlet" pathology. We introduce a gauge breaking module which decouples the mass of gauge partners from the mass of top partners, allowing for natural electroweak symmetry breaking. The collider phenomenology is dominated by production and decay of the top partners, which are considerably lighter than in traditional little Higgs theories.

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arXiv2009

Dark Matter Signals from Cascade Annihilations

A leading interpretation of the electron/positron excesses seen by PAMELA and ATIC is dark matter annihilation in the galactic halo. Depending on the annihilation channel, the electron/positron signal could be accompanied by a galactic gamma ray or neutrino flux, and the non-detection of such fluxes constrains the couplings and halo properties of dark matter. In this paper, we study the interplay of electron data with gamma ray and neutrino constraints in the context of cascade annihilation models, where dark matter annihilates into light degrees of freedom which in turn decay into leptons in one or more steps. Electron and muon cascades give a reasonable fit to the PAMELA and ATIC data. Compared to direct annihilation, cascade annihilations can soften gamma ray constraints from final state radiation by an order of magnitude. However, if dark matter annihilates primarily into muons, the neutrino constraints are robust regardless of the number of cascade decay steps. We also examine the electron data and gamma ray/neutrino constraints on the recently proposed "axion portal" scenario.

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arXiv2008

Naturally Flavorful Supersymmetry at the LHC

The suppression of flavor and CP violation in supersymmetric theories may be due to the mechanism responsible for the structure of the Yukawa couplings. We study model independently the compatibility between low energy flavor and CP constraints and observability of superparticles at the LHC, assuming a generic correlation between the Yukawa couplings and the supersymmetry breaking parameters. We find that the superpotential operators that generate scalar trilinear interactions are generically problematic. We discuss several ways in which this tension is naturally avoided. In particular, we focus on several frameworks in which the dangerous operators are naturally absent. These frameworks can be combined with many theories of flavor, including those with (flat or warped) extra dimensions, strong dynamics, or flavor symmetries. We show that the resulting theories can avoid all the low energy constraints while keeping the superparticles light. The intergenerational mass splittings among the sfermions can reflect the structure of the underlying flavor theory, and can be large enough to be measurable at the LHC. Detailed observations of the superparticle spectrum may thus provide new handles on the origin of the flavor structure of the standard model.

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