arXiv subjects
Publications and source records attributed to Alfredo Gurrola.
We consider a simplified model where a W' boson is added to the standard model with negligible couplings to quarks, but generic couplings to leptons and electroweak bosons. We study the implications of such a model for LHC searches. Consequently, we propose an LHC search through the vector boson fusion topology which would have sensitivity for such a new particle with the current proton-proton collisions's energy and available luminosity.
We perform a feasibility study to search for axion-like particles (ALPs) using vector boson fusion (VBF) processes at the LHC. We work in an effective field theory framework with cutoff scale $Λ$ and ALP mass $m_{a}$, and assume that ALPs couple to photons with strength $\propto 1/Λ$. Assuming proton-proton collisions at $\sqrt{s} = 13$ TeV, we present the total VBF ALP production cross sections, ALP decay widths and lifetimes, and relevant kinematic distributions as a function of $m_{a}$ and $Λ$. We consider the $a\toγγ$ decay mode to show that the requirement of an energetic diphoton pair combined with two forward jets with large dijet mass and pseudorapidity separation can significantly reduce the Standard Model backgrounds, leading to a $5σ$ discovery reach for $10 \text{ MeV} \lesssim m_{a} \lesssim 1$ TeV with $Λ\lesssim 2$ TeV, assuming an integrated luminosity of 3000 fb$^{-1}$. In particular, this extends the LHC sensitivity to a previously unstudied region of the ALP parameter space.
A new physics scenario shows that four-fermion operators of Nambu-Jona-Lasinio (NJL) type have a strong-coupling UV fixed point, where composite fermions $F$ (bosons $Π$) form as bound states of three (two) SM elementary fermions and they couple to their constituents via effective contact interactions at the composite scale $Λ\approx {\cal O} $(TeV). We present a phenomenological study to investigate such composite particles at the LHC by computing the production cross sections and decay widths of composite fermions in the context of the relevant experiments at the LHC with $pp$ collisions at $\sqrt{s}={\rm 13}$ TeV and $\sqrt{s}={\rm 14}$ TeV. Systematically examining all the different composite particles $F$ and the signatures with which they can manifest, we found a vast spectrum of composite particles $F$ that has not yet been explored at the LHC. Recasting the recent CMS results of the resonant channel $pp\rightarrow e^+F \rightarrow e^+e^- q\bar{q}'$, we find that the composite fermion mass $m_F$ below 4.25 TeV is excluded for $Λ$/$m_F$ = 1. We further highlight the region of parameter space where this specific composite particle $F$ can appear using 3 ab$^{-1}$, expected by the High-Luminosity LHC, computing 3 and 5 $σ$ contour plots of its statistical significance.
Dark matter that is electrically neutral but couples to the electromagnetic current through higher-dimensional operators constitutes an interesting class of models. We investigate this class of models at the Large Hadron Collider, focusing on the anapole moment operator in an effective field theory (EFT) framework, and utilizing the vector boson fusion (VBF) topology. Assuming proton-proton collisions at $\sqrt{s} = 13$ TeV, we present the VBF anapole dark matter (ADM) cross sections and kinematic distributions as functions of the free parameters of the EFT, the cutoff scale $Λ$ and the ADM mass $m_χ$. We find that the distinctive VBF topology of two forward jets and large dijet pseudorapidity gap is effective at reducing SM backgrounds, leading to a $5σ$ discovery reach for all kinematically allowed ADM masses with $Λ\le 1.65$ (1.15) TeV, assuming an integrated luminosity of 3000 (100) fb$^{-1}$.
New massive spin-2 particles are predicted in theoretical extensions to the Standard Model (SM) attempting to solve the hierarchy problem. Such theories postulate that gravity is diluted compared to the other fundamental forces because it can propagate in extra spatial dimensions. While such theoretical models are of high experimental interest because they predict massive spin-2 particles ($Y_{2}$) potentially detectable by collider experiments, searches at the Large Hadron Collider (LHC) have thus far produced no significant evidence for their existence. This work considers a hypothetical physics scenario where low coupling strengths between the $Y_{2}$ and quarks/gluons is the underlying reason behind the null $Y_{2}$ search results at the LHC, which have mainly relied on Drell-Yan and gluon-gluon fusion production mechanisms. The focus of this paper is a feasibility study to search for $Y_{2}$ particles using vector boson fusion (VBF) processes at the LHC. In the context of an effective field theory approach with varying couplings $κ_{V}$ between $Y_{2}$ and the weak bosons of the SM, we consider the $Y_{2}\toγγ$ decay mode to show that the requirement of a diphoton pair combined with two high $p_{T}$ forward jets with large dijet mass and with large separation in pseudorapidity can significantly reduce the SM backgrounds. Assuming proton-proton collisions at $\sqrt{s} = 13$ TeV, we present the total VBF production cross sections, $Y_{2}$ decay widths, and $Y_{2}\toγγ$ branching ratios as a function of $m(Y_{2})$, considering universal and non-universal couplings to the SM particles. The unitarity-violating phase space is described. The proposed VBF $Y_{2}\toγγ$ search is expected to achieve a discovery reach with signal significance greater than 5$σ$ for $Y_{2}$ masses up to 4.4 TeV and $κ_{V}$ couplings down to 0.5.
The identity of Dark Matter (DM) is one of the most captivating topics in particle physics today. The R-parity conserving Minimal Supersymmetric Standard Model (MSSM), which naturally provides a DM candidate in the form of the lightest neutralino ($\tildeχ_{1}^{0}$), is used as a benchmark scenario to show that a measurement of $Ω_{\tildeχ_{1}^{0}}h^{2}$ can be achieved from measurements at the CERN Large Hadron Collider. Focus is placed on compressed mass spectra regions, where the mass difference between the $\tildeχ_{1}^{0}$ and the $\tildeτ_{1}$ is small and where the $\tildeτ_{1}$-$\tildeχ_{1}^{0}$ coannihilation (CA) mechanism of the early Universe plays an important role. The technique for measuring $Ω_{\tildeχ_{1}^{0}}h^{2}$ relies on two proposed searches for compressed Supersymmetry (SUSY): 1) production via Vector Boson Fusion (VBF) processes; and 2) production with associated energetic jets from initial state radiation (ISR). These approaches allow for the determination of the relic abundance at the LHC for any model where CA is an important DM reduction mechanism in the early Universe. Thus, it is possible to confirm that the DM we observe today were $\tildeχ_{1}^{0}$'s created in the early Universe. We show that from measurements in the VBF and ISR SUSY searches at the LHC, the dark matter relic density can be measured with an uncertainty of 25\% with 3000 fb$^{-1}$ of 13 TeV proton-proton data.
We present a feasibility study, to search for dark matter at the LHC, in events with one soft hadronically decaying tau lepton and missing transverse energy recoiling against a hard $p_{T}$ jet from initial state radiation. This methodology allows the search for Supersymmetry in compressed mass spectra regions, where the mass difference between the lightest neutralino, $\tildeχ_1^0$, and the stau (the tau superpartner), $\tildeτ$, is small. Several theoretical models predict a direct connection between thermal Bino dark matter and staus within this scenario. We show that compressed regions, not excluded by ATLAS nor CMS experiments, are opened up with the increase in experimental sensitivity reached with the proposed methodology. The requirement of a hard jet from initial state radiation combined with a soft tau lepton is effective in reducing Standard Model backgrounds, providing expected significances greater than 3$σ$ for $\tildeχ_{1}^{\pm}$ masses up to 300 GeV and $\tildeτ$-$\tildeχ_{1}^{0}$ mass gaps below 25 GeV with only 30 fb$^{-1}$ of 13 TeV data from the LHC.
A feasibility study is presented for the search of the lightest bottom squark (sbottom) in a compressed scenario, where its mass difference from the lightest neutralino is 5 GeV. Two separate studies are performed: $(1)$ final state containing two VBF-like tagging jets, missing transverse energy, and zero or one $b$-tagged jet; and $(2)$ final state consisting of initial state radiation (ISR) jet, missing transverse energy, and at least one $b$-tagged jet. An analysis of the shape of the missing transverse energy distribution for signal and background is performed in each case, leading to significant improvement over a cut and count analysis, especially after incorporating the consideration of systematics and pileup. The shape analysis in the VBF-like tagging jet study leads to a $3σ$ exclusion potential of sbottoms with mass up to $530 \, (462)$ GeV for an integrated luminosity of $300$ fb$^{-1}$ at 14 TeV, with $5\%$ systematics and PU $= 0 \, (50)$.
The vector boson fusion (VBF) topology at the Large Hadron Collider at 14 TeV provides an opportunity to search for new physics. A feasibility study for the search of sleptons in a compressed mass spectra scenario is presented in the final state of two jets, one or two low $p_{T}$ non-resonant leptons, and missing energy. The presence of the VBF tagged jets and missing energy are effective in reducing Standard Model backgrounds. Using smuon production with a mass difference between $\tilde{l}_{L}$ and $\tildeχ_{1}^0$ of 5-15 GeV, the significance of observing the signal events is found to be $\sim$ 3-6$σ$ for $m_{\tilde{l}}$=115-135 GeV, considering an integrated luminosity of 3000 fb$^{-1}$.
A feasibility study is presented for the search of the lightest top squark in a compressed scenario, where its mass is approximately equal to the sum of the masses of the top quark and the lightest neutralino. The study is performed in the final state of two b-jets, one lepton, large missing energy, and two high-$E_{\rm T}$ jets with large separation in pseudo-rapidity, in opposite hemispheres, and with large dijet mass. The LHC could discover compressed top squarks with mass up to approximately 340 GeV (390 GeV) with an integrated luminosity of 1000 ifb (3000 ifb).
Vector boson fusion (VBF) processes at the Large Hadron Collider (LHC) provide a unique opportunity to search for new physics with electroweak couplings. Two studies are presented: (i) A search of supersymmetric dark matter in the final state of two VBF jets and large missing transverse energy is presented at 14 TeV. Prospects for determining the dark matter relic density are studied for the cases of Wino and Bino-Higgsino dark matter. The LHC could probe Wino dark matter with mass up to approximately 600 GeV with a luminosity of 1000 fb$^{-1}$. (ii) A search for the chargino/neutralino system in the final state of two VBF jets, missing transverse energy and two $τ$'s (light stau case) and light lepton $e$ and $μ$ (light slepton case). The $5 σ$ mass reach at 300 fb$^{-1}$ (1000 fb$^{-1}$) of LHC14 for inclusive and opposite-sign $τ$ pairs are 250 GeV (300 GeV) and 200 GeV (250 GeV), respectively, for $ΔM \, = \, m_{\tildeτ_1} - m_{\neu{1}} \, = \, 30$ GeV. For $ΔM \, = \, 15$ GeV, the $3 σ$ mass reach at 300 fb$^{-1}$ (1000 fb$^{-1}$) of LHC14 for inclusive $τ$ pairs is 180 GeV. The $5 σ$ mass reach at 300 fb$^{-1}$ (1000 fb$^{-1}$) of LHC14 for inclusive and opposite-sign $μ$ pairs are approximately 350 GeV (400 GeV) and 300 GeV (350 GeV), respectively. The mass reaches in the same-sign final state cases are similar to those in the opposite-sign cases.
Vector boson fusion (VBF) processes at the Large Hadron Collider (LHC) provide a unique opportunity to search for new physics with electroweak couplings. A feasibility study for the search of supersymmetric dark matter in the final state of two VBF jets and large missing transverse energy is presented at 14 TeV. Prospects for determining the dark matter relic density are studied for the cases of Wino and Bino-Higgsino dark matter. The LHC could probe Wino dark matter with mass up to approximately 600 GeV with a luminosity of 1000 fb$^{-1}$.
Vector boson fusion (VBF) processes offer a promising avenue to study the non-colored sectors of supersymmetric extensions of the Standard Model at the LHC. A feasibility study for searching for the chargino/neutralino system in the $R-$parity conserving Minimal Supersymmetric Standard Model is presented. The high $E_T$ forward jets in opposite hemispheres are utilized to trigger VBF events, so that the production of the lightest chargino and the second lightest neutralino can be probed without a bias by experimental triggers. Kinematic requirements are developed to search for signals of these supersymmetric states above Standard Model backgrounds in both $τ$ and light lepton ($e$ and $μ$) final states at $\sqrt{s} = 8$ TeV.
We investigate the minimal supergravity (mSUGRA) signals at the LHC in the context of supercritical string cosmology (SSC). In this theory, the presence of a time dependent dilaton provides us with a smoothly evolving dark energy and modifies the dark matter allowed region of the mSUGRA model with standard cosmology. Such a dilaton dilutes the supersymmetric dark matter density (of neutralinos) by a factor O(10) and consequently the regions with too much dark matter in the standard scenario are allowed in the SSC. The final states expected at the LHC in this scenario, unlike the standard scenario, consist of Z bosons, Higgs bosons, and/or high energy taus. We show how to characterize these final states and determine the model parameters. Using these parameters, we determine the dark matter content and the neutralino-proton cross section. All these techniques can also be applied to determine model parameters in SSC models with different SUSY breaking scenarios.
We examine the stau-neutralino coannihilation (CA) mechanism of the early universe. We use the minimal supergravity (mSUGRA) model and show that from measurements at the Large Hadron Collider one can predict the dark matter relic density with an uncertainty of 6% with 30 fb-1 of data, which is comparable to the direct measurement by Wilkinson Microwave Anisotropy Probe. This is done by measuring four mSUGRA parameters m0, m1/2, A0 and tan(beta) without requiring direct measurements of the top squark and bottom squark masses. We also provide precision measurements of the gaugino, squark, and lighter stau masses in this CA region without assuming gaugino universality.