arXiv subjects

Patricia Rebello Teles

Publications and source records attributed to Patricia Rebello Teles.

11 recordsLinked to original sources

arXiv2024

Searches for axion-like particles via $γγ$ fusion at future $\mathrm{e}^+\mathrm{e}^-$ colliders

Opportunities for searches for axion-like particles (ALPs) coupling to photons in $\mathrm{e}^+\mathrm{e}^-$ collisions at the Future Circular Collider (FCC-ee) and International Linear Collider (ILC) are investigated. We perform a study of the photon-fusion production of ALPs decaying into two photons, $\mathrm{e}^+\mathrm{e}^- \overset{γγ}{\longrightarrow} \mathrm{e}^{+}\;a(γγ)\;\mathrm{e}^{-}$, over the light-by-light continuum background, for the planned FCC-ee and ILC center-of-mass energies and integrated luminosities. An analysis of the feasibility measurements is presented using parametrized simulations for two types of detectors. Upper limits at 95% confidence level (CL) on the cross section for ALP production, $σ(γγ\to a \to γγ)$, and on the ALP-photon coupling are obtained over the $m_a \approx 0.1$--1000 GeV ALP mass range, and compared to current and future collider searches. Production cross sections down to $σ(γγ\to a \to γγ) \approx 1$ fb (1 ab) will be probed at $m_a\approx 1$ (300) GeV, corresponding to constraints on the axion-photon coupling as low as $g_\mathrm{aγγ} \approx 2\cdot10^{-3}$ TeV$^{-1}$.

hep-ex↗

arXiv2020

New opportunities at the photon energy frontier

Ultra-peripheral collisions (UPCs) involving heavy ions and protons are the energy frontier for photon-mediated interactions. UPC photons can be used for many purposes, including probing low-$x$ gluons via photoproduction of dijets and vector mesons, probes of beyond-standard-model processes, such as those enabled by light-by-light scattering, and studies of two-photon production of the Higgs.

hep-ph↗

arXiv2020

Higgs boson production in photon-photon interactions with proton, light-ion, and heavy-ion beams at current and future colliders

The production of the Higgs boson in photon-photon interactions with proton and nucleus beams at three planned or proposed future CERN colliders --- the high-luminosity Large Hadron Collider (HL-LHC), the high-energy LHC (HE-LHC), and the Future Circular Collider (FCC) --- is studied. The cross sections for the process AA$\xrightarrow{γγ}$(A)H(A), with the ions A surviving the interaction and the Higgs scalar exclusively produced, are computed with MadGraph 5 modified to include the corresponding elastic $γ$ fluxes, for Pb-Pb, Xe-Xe, Kr-Kr, Ar-Ar, O-O, p-Pb, and p-p over the nucleon-nucleon collision energy range $\sqrt{s}\approx 3$--100 TeV. Simulations of the $γγ\to H \to b\bar{b}$ decay mode --- including realistic (mis)tagging and reconstruction efficiencies for the final-state b-jets, as well as appropriate kinematical selection criteria to reduce the similarly computed $γγ\to b\bar{b},c\bar{c},q\bar{q}$ continuum backgrounds --- have been carried out. Taking into account the expected luminosities for all systems, the yields and significances for observing the Higgs boson in ultraperipheral collisions (UPCs) are estimated. At the HL-LHC and HE-LHC, the colliding systems with larger Higgs significance are Ar-Ar(6.3 TeV) and Kr-Kr(12.5 TeV) respectively, but $3σ$ evidence for two-photon Higgs production would require 200 and 30 times larger integrated luminosities than those planned today at both machines. Factors of ten can be gained by running for a year, rather than the typical 1-month heavy-ion LHC operation, but the process will likely remain unobserved until a higher energy hadron collider, such as the FCC, is built. In the latter machine, the $5σ$ observation of Higgs production in UPCs is feasible in just the first nominal run of Pb-Pb and p-Pb collisions at $\sqrt{s} = 39$ and 63 TeV respectively.

hep-ph↗

arXiv2018

PHOTON-2017 conference proceedings

This document collects the proceedings of the PHOTON 2017 conference ("International Conference on the Structure and the Interactions of the Photon", including the 22th "International Workshop on Photon-Photon Collisions", and the "International Workshop on High Energy Photon Colliders") held at CERN (Geneva) in May 2017. The latest experimental and theoretical developments on the topics of the PHOTON conference series are covered: (i) $γ\,γ$ processes in e$^+$e$^-$, proton-proton (pp) and nucleus-nucleus (AA) collisions at current and future colliders, (ii) $γ$-hadron interactions in e$^\pm$p, pp, and AA collisions, (iii) final-state photon production (including Standard Model studies and searches beyond it) in pp and AA collisions, and (iv) high-energy $γ$-ray astrophysics. These proceedings are dedicated to the memory of Maria Krawczyk.

hep-ph↗

arXiv2018

Prospects for $γγ\to$ Higgs observation in ultraperipheral ion collisions at the Future Circular Collider

We study the two-photon production of the Higgs boson, $\rm γγ\to H$, at the Future Circular Collider (FCC) in ultraperipheral PbPb and pPb collisions at $\sqrt{s_{NN}} = 39$ and 63 TeV. Signal and background events are generated with MADGRAPH 5, including $γ$ fluxes from the proton and lead ions in the equivalent photon approximation, yielding $\rm σ(γγ\to H)$ = 1.75 nb and 1.5 pb in PbPb and pPb collisions respectively. We analyse the H$\,\to b\bar{b}$ decay channel including realistic reconstruction efficiencies for the final-state $b$-jets, showered and hadronized with PYTHIA 8, as well as appropriate selection criteria to reduce the dominant exclusive $γγ\to b\bar{b}$ continuum background. Observation of $\rm PbPb\xrightarrow{γγ}(Pb)\,H\,(Pb)$ is achievable in the first year with the expected PbPb integrated luminosities.

hep-ph↗

arXiv2017

Measurements of $γγ\to \mbox{Higgs}$ and $γγ\to W^{+}W^{-}$ in $e^{+}e^{-}$ collisions at the Future Circular Collider

The measurements of the two-photon production of the Higgs boson and of $W^{\pm}$ boson pairs in $e^{+}e^{-}$ collisions at the Future Circular Collider (FCC-ee) are investigated. The processes $e^{+}e^{-}\xrightarrow{γγ}e^+\,{\rm H}\,e^-,e^+\,{\rm W^+W^-}\,e^-$ are computed using the effective photon approximation for electron-positron beams, and studied in their ${\rm H}\to b\bar{b}$ and ${\rm W^+W^-}\to 4j$ decay final-states including parton showering and hadronization, jet reconstruction, $e^\pm$ forward tagging, and realistic experimental cuts. After selection criteria, up to 75 Higgs bosons and 6600 $\rm W^{\pm}$ pairs will be reconstructed on top of controllable continuum backgrounds at $\sqrt{s} = $240 and 350 GeV for the total expected integrated luminosities, by tagging the scattered $e^\pm$ with near-beam detectors. A 5$σ$ observation of $γγ\to$H is thereby warranted, as well as high-statistics studies of triple $\rm γWW$ and quartic $\rm γγWW$ electroweak couplings, improving by at least factors of 2 and 10 the current limits on dimension-6 anomalous quartic gauge couplings.

hep-ph↗

arXiv2017

Sharpening the shape analysis for higher-dimensional operator searches

When the Standard Model is interpreted as the renormalizable sector of a low-energy effective theory, the effects of new physics are encoded into a set of higher dimensional operators. These operators potentially deform the shapes of Standard Model differential distributions of final states observable at colliders. We describe a simple and systematic method to obtain optimal estimations of these deformations when using numerical tools, like Monte Carlo simulations. A crucial aspect of this method is minimization of the estimation uncertainty: we demonstrate how the operator coefficients have to be set in the simulations in order to get optimal results. The uncertainty on the interference term turns out to be the most difficult to control and grows very quickly when the interference is suppressed. We exemplify our method by computing the deformations induced by the ${\cal O}_{3W}$ operator in $W^+W^-$ production at the LHC, and by deriving a bound on ${\cal O}_{3W}$ using $8$ TeV CMS data.

hep-ph↗

arXiv2015

Prospects for $γγ\to H$ and $γγ\to W^{+}W^{-}$ measurements at the FCC-ee

We study the possibilities for the measurement of two-photon production of the Higgs boson (in the $b \bar{b}$ decay channel), and of $W^{+}W^{-}$ pairs (decaying into four jets) in $e^{+}e^{-}$ collisions at the the Future Circular Collider (FCC-ee). The processes are simulated with the PYTHIA and MADGRAPH 5 Monte Carlo codes, using the effective photon approximation for the $e^{+}e^{-}$ photon fluxes, at center-of-mass energies $\sqrt{s} = $ 160 GeV and 240 GeV. The analyses include electron-positron tagging, realistic acceptance and reconstruction efficiencies for the final-state jets, and selection criteria to remove the backgrounds. Observation of both channels is achievable with the expected few ab$^{-1}$ integrated luminosities at FCC-ee.

hep-ph↗

arXiv2014

Excluding the Light Dark Matter Window of a 331 Model Using LHC and Direct Dark Matter Detection Data

We sift the impact of the recent Higgs precise measurements, and recent dark matter direct detection results, on the dark sector of an electroweak extension of the Standard Model that has a complex scalar as dark matter. We find that in this model the Higgs decays with a large branching ratio into dark matter particles, and charged scalars when these are kinematically available, for any coupling strength differently from the so called Higgs portal. Moreover, we compute the abundance and spin-independent WIMP-nucleon scattering cross section, which are driven by the Higgs and $Z^{\prime}$ boson processes. We decisively exclude the $1-500$~GeV dark matter window and find the most stringent lower bound in the literature on the scale of symmetry breaking of the model namely $10$~TeV, after applying the LUX-2013 limit. Interestingly, the projected XENON1T constraint will be able to rule out the entire $1$~GeV-$1000$~GeV dark matter mass range. Lastly, for completeness, we compute the charged scalar production cross section at the LHC and comment on the possibility of detection at current and future LHC runnings.

hep-ph↗

arXiv2013

Search for anomalous gauge couplings in semi-leptonic decays of $WWγ$ and $WZγ$ in pp collisions at $\sqrt{s} =$ 8 TeV

A study of the Standard Model (SM) three electroweak boson production, $WVγ$ where V = W or Z gauge boson, is presented concerning events with a leptonically decaying W boson accompanied by a photon and two or more jets. We are using the full 2012 dataset, of proton-proton collisions at a center-of-mass energy of 8 TeV and an integrated luminosity of 19.3 fb${}^{-1}$, collected by the CMS detector at the Large Hadron Collider (LHC). $WVγ$ production final states may be sensitive to anomalous $WWγγ$ and $WWZγ$ quartic couplings. In light of the recent discovery of a Higgs-like particle, we investigate, in a model independent way, any deviation of gauge boson couplings with respect to the SM prediction by setting limits on the anomalous quartic gauge couplings (aQGC) for $WWγγ$ and $WWZγ$. Upper limits at 95% confidence level are obtained, with and without a form factor.

hep-ex↗

arXiv2013

Searches for New Physics in the Standard Model's Electroweak Sector: Quartic Anomalous Couplings with Vector Boson Fusion and Flavor Changed Neutral Current in the $SU(3)_{C}\otimes SU(3)_{L}\otimes U(1)_{X}$ model

In this thesis we investigated, at partonic level and leading order, the LHC potencial operating with $\sqrt{s}=14$ TeV and integrated luminosity of $L=100\;{fb}^{-1}$ to probe "pure" (without triple vertex contributions) anomalous electroweak quartic couplings, $WWWW$ and $WWZZ$, in the semileptonic $pp \rightarrow l^{\pm}ν_{l}jjjj$ channel, enhanced by the Vector Boson Fusion collider signatures. Deviations on SM quartic couplings were parameterized in a model independent approach, realized linearly ($L_{S0}$ and $L_{S1}$ operators) or not ($L_{4}$ and $L_{5}$ operators), on the basis of effective lagrangians. Being our analysis essentially events counting-and-cut based, we took into account all possible backgrounds (irreducible, QCD and top quarks processes) considered at ${\cal O}(α_{em}^{6})$, ${\cal O(α_{em}^{4}α_{s}^{2})$ and ${\cal O}(α_{em}^{2}α_{s}^{4})$. In this way, we have obtained the following constraints for the non-linear $α_{4}$ and $α_{5}$ anomalous couplings: $|α_{4,5}| \lesssim 0.01$ to 0.02 at 3$σ$. Based on non-linear results, we have estimated, for a specific choice of factorization and renormalization scale, the linear parameters $f_{0}$ and $f_{1}$ constraints as $-22 \leq \dfrac{f_{0}}{Λ^{4}}\;({TeV}^{-4}) \leq 20, \quad {and} \quad -26 \leq \dfrac{f_{1}}{Λ^{4}}\;({TeV}^{-4}) \leq 24$ at 3$σ$. On a different approach, manipulating one extension of the SM named $331_{RHN}$, we have evaluated the contribution of new sources of FCNC for the difference of mass of neutral meson systems, $K_{0}-\bar{K_{0}}$, $D^{0}-\bar{D^0}$ and $B^0_d-\bar{B^0_d}$. Bounds related to these systems may be significantly strengthened in the presence of these new interactions allowing stronger constraints on the parameter space of the model.

hep-ph↗