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Ying-Ying Li

Publications and source records attributed to Ying-Ying Li.

46 records · Page 3Linked to original sources
arXiv2018

Complete One-Loop Matching for a Singlet Scalar in the Standard Model EFT

We present the results of the first complete one-loop matching calculation between the real singlet scalar extension of the Standard Model and the Standard Model effective field theory (SMEFT) at dimension six. Beyond their immediate relevance to the precision calculation of observables in singlet extensions of the Standard Model, our results illustrate a variety of general features of one-loop matching. We explore the interplay between non-supersymmetric non-renormalization theorems, the logarithmic dependence of Wilson coefficients, and the relevance of mixed diagrams in theories with large scale separation. In addition, we highlight some of the subtleties involved in computing observables at next-to-leading order in SMEFT by mapping our results to the $T$ parameter at one loop.

hep-ph↗
arXiv2018

Twin Turtles

We present an ultraviolet extension of the Twin Higgs in which the radial mode of twin symmetry breaking is itself a pseudo-goldstone boson. This "turtle" structure raises the scale of new colored particles in exchange for additional states in the Higgs sector, making multiple Higgs-like scalars the definitive signature of naturalness in this context. We explore the parametrics and phenomenology of a concrete Twin Turtle model and demonstrate its robustness in two different supersymmetric completions. Along the way, we also introduce a new mechanism for inducing hard twin symmetry-breaking quartics via soft supersymmetry breaking.

hep-ph↗
arXiv2018

Novelty Detection Meets Collider Physics

Novelty detection is the machine learning task to recognize data, which belong to an unknown pattern. Complementary to supervised learning, it allows to analyze data model-independently. We demonstrate the potential role of novelty detection in collider physics, using autoencoder-based deep neural network. Explicitly, we develop a set of density-based novelty evaluators, which are sensitive to the clustering of unknown-pattern testing data or new-physics signal events, for the design of detection algorithms. We also explore the influence of the known-pattern data fluctuations, arising from non-signal regions, on detection sensitivity. Strategies to address it are proposed. The algorithms are applied to detecting fermionic di-top partner and resonant di-top productions at LHC, and exotic Higgs decays of two specific modes at a $e^+e^-$ future collider. With parton-level analysis, we conclude that potentially the new-physics benchmarks can be recognized with high efficiency.

hep-ph↗
arXiv2017

Neutrinos in Large Extra Dimensions and Short-Baseline $ν_e$ Appearance

We show that, in the presence of bulk masses, sterile neutrinos propagating in large extra dimensions (LED) can induce electron-neutrino appearance effects. This is in contrast to what happens in the standard LED scenario and hence LED models with explicit bulk masses have the potential to address the MiniBooNE and LSND appearance results, as well as the reactor and Gallium anomalies. A special feature in our scenario is that the mixing of the first KK modes to active neutrinos can be suppressed, making the contribution of heavier sterile neutrinos to oscillations relatively more important. We study the implications of this neutrino mass generation mechanism for current and future neutrino oscillation experiments, and show that the Short-Baseline Neutrino Program at Fermilab will be able to efficiently probe such a scenario. In addition, this framework leads to massive Dirac neutrinos and thus precludes any signal in neutrinoless double beta decay experiments.

hep-ph↗
arXiv2017

Optimizing Higgs factories by modifying the recoil mass

It is difficult to measure the $WW$-fusion Higgs production process ($e^+e^- \to ν\barν h$) at a lepton collider with a center of mass energy of 240-250 GeV due to its small rate and the large background from the Higgsstrahlung process with an invisible $Z$ ($e^+e^- \to hZ,\,Z\to ν\barν$). We construct a modified recoil mass variable, $m^p_{\rm recoil}$, defined using only the 3-momentum of the reconstructed Higgs particle, and show that it can better separate the $WW$-fusion and Higgsstrahlung events than the original recoil mass variable $m_{\rm recoil}$. Consequently, the $m^p_{\rm recoil}$ variable can be used to improve the overall precisions of the extracted Higgs couplings, in both the conventional framework and the effective-field-theory framework. We also explore the application of the $m^p_{\rm recoil}$ variable in the inclusive cross section measurements of the Higgsstrahlung process, while a quantitive analysis is left for future studies.

hep-ph↗
arXiv2017

Heavy Higgs Bosons at Low $\tan β$: from the LHC to 100 TeV

We present strategies to search for heavy neutral Higgs bosons decaying to top quark pairs, as often occurs at low $\tan β$ in type II two Higgs doublet models such as the Higgs sector of the MSSM. The resonant production channel is unsatisfactory due to interference with the SM background. We instead propose to utilize same-sign dilepton signatures arising from the production of heavy Higgs bosons in association with one or two top quarks and subsequent decay to a top pair. We find that for heavier neutral Higgs bosons the production in association with one top quark provides greater sensitivity than production in association with two top quarks. We obtain current limits at the LHC using Run I data at 8 TeV and forecast the sensitivity of a dedicated analysis during Run II at 14 TeV. Then we perform a detailed BDT study for the 14 TeV LHC and a future 100 TeV collider.

hep-ph↗
arXiv2016

Lepton-Flavored Electroweak Baryogenesis

We explore lepton-flavored electroweak baryogenesis, driven by CP-violation in leptonic Yukawa sector, using the $τ-μ$ system in the two Higgs doublet model as an example. This setup generically yields, together with the flavor-changing decay $h\to τμ$, a tree-level Jarlskog-invariant that can drive dynamical generation of baryon asymmetry during a first-order electroweak phase transition and results in CP-violating effect in the decay $h\to ττ$. We find that the observed baryon asymmetry can be generated in parameter space compatible with current experimental results for the decays $h\to τμ$, $h\to ττ$ and $τ\rightarrow μγ$, as well as the present bound on the electric dipole moment of the electron. The baryon asymmetry generated is intrinsically correlated with the CP-violating decay $h\to ττ$ and the flavor-changing decay $h\to τμ$, which thus may serve as "smoking guns" to test lepton-flavored electroweak baryogenesis.

hep-ph↗
arXiv2016

750 GeV Resonance in the Gauged $U(1)'$-Extended MSSM

Recently the ATLAS and CMS collaborations at the LHC announced their observation of a potential 750 GeV di-photon resonance, after analyzing the $\sqrt{s}=13$ TeV LHC data. This observation has significant implications for low-energy supersymmetry. Beyond the MSSM and the NMSSM, we study the MSSM-extensions with an extra $U(1)'$ gauge symmetry. The anomaly cancellation and the spontaneous breaking of the non-decoupled $U(1)'$ generically require introducing vector-like supermultiplets (both colored and color-neutral ones) and singlet supermultiplets, respectively. We illustrate that the potential 750 GeV resonance ($Y$) can be accommodated in various mechanisms, as a singlet-like scalar or pseudoscalar. Three benchmark scenarios are presented: (1) vector-like quarks (VLQ) mediated $pp \to Y \to γγ$; (2) scalar VLQ mediated $pp \to Y \to γγ$; (3) heavy scalar (pseudo-scalar) $H/A$ associated production $pp \to H^*/A^* \to Y H/h$. Additionally, we notice that the $Z'$-mediated vector boson fusion production and $Z'$-associated production $pp \to Y qq'$, if yielding a signal rate of the observed level, might have been excluded by the searches for $Z'$ via Drell-Yan process at the LHC.

hep-ph↗
arXiv2015

Heavy Higgs Bosons at 14 TeV and 100 TeV

Searching for Higgs bosons beyond the Standard Model (BSM) is one of the most important missions for hadron colliders. As a landmark of BSM physics, the MSSM Higgs sector at the LHC is expected to be tested up to the scale of the decoupling limit of O(1) TeV, except for a wedge region centered around $\tanβ\sim 3 -10$, which has been known to be difficult to probe. In this article, we present a dedicated study testing the decoupled MSSM Higgs sector, at the LHC and a next-generation $pp$-collider, proposing to search in channels with associated Higgs productions, with the neutral and charged Higgs further decaying into $tt$ and $tb$, respectively. In the case of neutral Higgs we are able to probe for the so far uncovered wedge region via $pp\to bb H/A \to bbtt$. Additionally, we cover the the high $\tanβ$ range with $pp\to bb H/A \to bbττ$. The combination of these searches with channels dedicated to the low $\tanβ$ region, such as $pp\to H/A \to tt$ and $pp\to tt H/A \to tttt$ potentially covers the full $\tanβ$ range. The search for charged Higgs has a slightly smaller sensitivity for the moderate $\tanβ$ region, but additionally probes for the higher and lower $\tanβ$ regions with even greater sensitivity, via $pp\to tb H^\pm \to tbtb$. While the LHC will be able to probe the whole $\tanβ$ range for Higgs masses of O(1) TeV by combining these channels, we show that a future 100 TeV $pp$-collider has a potential to push the sensitivity reach up to $\sim \mathcal O(10)$ TeV. In order to deal with the novel kinematics of top quarks produced by heavy Higgs decays, the multivariate Boosted Decision Tree (BDT) method is applied in our collider analyses. The BDT-based tagging efficiencies of both hadronic and leptonic top-jets, and their mutual fake rates as well as the faking rates by other jets ($h$, $Z$, $W$, $b$, etc.) are also presented.

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