F. J. Munoz Sanchez’s research while affiliated with University of Manchester and other places

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Publications (154)


Search for a light charged Higgs boson in tH±bt \rightarrow H^{\pm } b decays, with H±csH^{\pm } \rightarrow cs, in pp collisions at s=13 TeV\sqrt{s}={13}\hbox { TeV} with the ATLAS detector
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February 2025

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9 Reads

The European Physical Journal C

G. Aad

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B. Abbott

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L. Zwalinski

A search for a light charged Higgs boson produced in decays of the top quark, tH±bt \rightarrow H^{\pm } b t → H ± b with H±csH^{\pm } \rightarrow cs H ± → c s , is presented. This search targets the production of top-quark pairs ttˉWbH±bt\bar{t} \rightarrow Wb H^{\pm } b t t ¯ → W b H ± b , with WνW \rightarrow \ell \nu W → ℓ ν ( =e,μ\ell = e, \mu ℓ = e , μ ), resulting in a lepton-plus-jets final state characterised by an isolated electron or muon and at least four jets. The search exploits b -quark and c -quark identification techniques as well as multivariate methods to suppress the dominant ttˉt\bar{t} t t ¯ background. The data analysed correspond to 140 fb1140\hbox { fb}^{-1} 140 fb - 1 of pp pp collisions at s=13 TeV\sqrt{s} = 13\hbox { TeV} s = 13 TeV recorded with the ATLAS detector at the LHC between 2015 and 2018. Observed (expected) 95% confidence-level upper limits on the branching fraction B(tH±b)\mathscr {B}(t\rightarrow H^{\pm } b) B ( t → H ± b ) , assuming B(tWb)+B(tH±(cs)b)=1.0\mathscr {B}(t\rightarrow Wb) + \mathscr {B}(t \rightarrow H^{\pm } (\rightarrow cs)b)=1.0 B ( t → W b ) + B ( t → H ± ( → c s ) b ) = 1.0 , are set between 0.066% (0.077%) and 3.6% (2.3%) for a charged Higgs boson with a mass between 60 and 168 GeV.

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Combination of searches for singly produced vectorlike top quarks in p p collisions at s = 13 TeV with the ATLAS detector

January 2025

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3 Reads

Physical Review D

A combination of searches for the single production of vectorlike top quarks ( T ) is presented. These analyses are based on proton-proton collisions at s = 13 TeV recorded in 2015–2018 with the ATLAS detector at the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb − 1 . The T decay modes considered in this combination are into a top quark and either a Standard Model Higgs boson or a Z boson ( T → H t and T → Z t ). The individual searches used in the combination are differentiated by the number of leptons ( e , μ ) in the final state. The observed data are found to be in good agreement with the Standard Model background prediction. Interpretations are provided for a range of masses and couplings of the vectorlike top quark for benchmark models and generalized representations in terms of 95% confidence level limits. For a benchmark signal prediction of a vectorlike top quark SU(2) singlet with electroweak coupling, κ , of 0.5, masses below 2.1 TeV are excluded, resulting in the most restrictive limits to date. © 2025 CERN, for the ATLAS Collaboration 2025 CERN


Search for boosted low-mass resonances decaying into hadrons produced in association with a photon in pp collisions at s \sqrt{s} = 13 TeV with the ATLAS detector

January 2025

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1 Read

Journal of High Energy Physics

G. Aad

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B. Abbott

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L. Zwalinski

A bstract Many extensions of the Standard Model, including those with dark matter particles, propose new mediator particles that decay into hadrons. This paper presents a search for such low mass narrow resonances decaying into hadrons using 140 fb − 1 of proton-proton collision data recorded with the ATLAS detector at a centre-of-mass energy of 13 TeV. The resonances are searched for in the invariant mass spectrum of large-radius jets with two-pronged substructure that are recoiling against an energetic photon from initial state radiation, which is used as a trigger to circumvent limitations on the maximum data recording rate. This technique enables the search for boosted hadronically decaying resonances in the mass range 20–100 GeV hitherto unprobed by the ATLAS Collaboration. The observed data are found to agree with Standard Model predictions and 95% confidence level upper limits are set on the coupling of a hypothetical new spin-1 Z ′ resonance with Standard Model quarks as a function of the assumed Z ′-boson mass in the range between 20 and 200 GeV.


Figure 16. Summary of quantitative comparisons for each observable measurement to predictions in form of p-values. This summary refers to observables measured in the phase space with at least three b-jets. The theoretical uncertainties in the MC predictions are not taken into account when computing the p-values.
Measurement of tt t\overline{t} production in association with additional b-jets in the eμ final state in proton–proton collisions at s \sqrt{s} = 13 TeV with the ATLAS detector

January 2025

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16 Reads

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1 Citation

Journal of High Energy Physics

A bstract This paper presents measurements of top-antitop quark pair ( tt t\overline{t} t t ¯ ) production in association with additional b -jets. The analysis utilises 140 fb − 1 of proton–proton collision data collected with the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy of 13 TeV. Fiducial cross-sections are extracted in a final state featuring one electron and one muon, with at least three or four b -jets. Results are presented at the particle level for both integrated cross-sections and normalised differential cross-sections, as functions of global event properties, jet kinematics, and b -jet pair properties. Observable quantities characterising b -jets originating from the top quark decay and additional b -jets are also measured at the particle level, after correcting for detector effects. The measured integrated fiducial cross-sections are consistent with ttbb t\overline{t}b\overline{b} t t ¯ b b ¯ predictions from various next-to-leading-order matrix element calculations matched to a parton shower within the uncertainties of the predictions. State-of-the-art theoretical predictions are compared with the differential measurements; none of them simultaneously describes all observables. Differences between any two predictions are smaller than the measurement uncertainties for most observables.


Search for diphoton resonances in the 66 to 110 GeV mass range using pp collisions at s \sqrt{s} = 13 TeV with the ATLAS detector

January 2025

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9 Reads

Journal of High Energy Physics

A bstract A search is performed for light, spin-0 bosons decaying into two photons in the 66 to 110 GeV mass range, using 140 fb − 1 of proton-proton collisions at s \sqrt{s} s = 13 TeV produced by the Large Hadron Collider and collected by the ATLAS detector. Multivariate analysis techniques are used to define event categories that improve the sensitivity to new resonances beyond the Standard Model. A model-independent search for a generic spin-0 particle and a model-dependent search for an additional low-mass Higgs boson are performed in the diphoton invariant mass spectrum. No significant excess is observed in either search. Mass-dependent upper limits at the 95% confidence level are set in the model-independent scenario on the fiducial cross-section times branching ratio into two photons in the range of 8 fb to 53 fb. Similarly, in the model-dependent scenario upper limits are set on the total cross-section times branching ratio into two photons as a function of the Higgs boson mass in the range of 19 fb to 102 fb.


Simultaneous Unbinned Differential Cross-Section Measurement of Twenty-Four Z + jets Kinematic Observables with the ATLAS Detector

December 2024

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45 Reads

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6 Citations

Physical Review Letters

Z boson events at the Large Hadron Collider can be selected with high purity and are sensitive to a diverse range of QCD phenomena. As a result, these events are often used to probe the nature of the strong force, improve Monte Carlo event generators, and search for deviations from standard model predictions. All previous measurements of Z boson production characterize the event properties using a small number of observables and present the results as differential cross sections in predetermined bins. In this analysis, a machine learning method called is used to produce a simultaneous measurement of twenty-four Z + jets observables using 139 fb − 1 of proton-proton collisions at s = 13 TeV collected with the ATLAS detector. Unlike any previous fiducial differential cross-section measurement, this result is presented unbinned as a dataset of particle-level events, allowing for flexible reuse in a variety of contexts and for new observables to be constructed from the twenty-four measured observables. © 2024 CERN, for the ATLAS Collaboration 2024 CERN


Underlying-event studies with strange hadrons in pp collisions at s=13\sqrt{s} = 13 TeV with the ATLAS detector

December 2024

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15 Reads

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1 Citation

The European Physical Journal C

Properties of the underlying-event in pp interactions are investigated primarily via the strange hadrons KS0K_{S}^{0} K S 0 , Λ\Lambda Λ and Λˉ\bar{\Lambda } Λ ¯ , as reconstructed using the ATLAS detector at the LHC in minimum-bias pp collision data at s=13\sqrt{s} = 13 s = 13 TeV. The hadrons are reconstructed via the identification of the displaced two-particle vertices corresponding to the decay modes "Equation missing" , Λπp\Lambda \rightarrow \pi ^-p Λ → π - p and Λˉπ+pˉ\bar{\Lambda }\rightarrow \pi ^+\bar{p} Λ ¯ → π + p ¯ . These are used in the construction of underlying-event observables in azimuthal regions computed relative to the leading charged-particle jet in the event. None of the hadronisation and underlying-event physics models considered can describe the data over the full kinematic range considered. Events with a leading charged-particle jet in the range of 10<pT4010 < p_T \le 40 10 < p T ≤ 40 GeV are studied using the number of prompt charged particles in the transverse region. The ratio N(Λ+Λˉ)/N(KS0)N(\Lambda + \bar{\Lambda })/N(K_{S}^{0}) N ( Λ + Λ ¯ ) / N ( K S 0 ) as a function of the number of such charged particles varies only slightly over this range. This disagrees with the expectations of some of the considered Monte Carlo models.


Operation and performance of the ATLAS tile calorimeter in LHC Run 2

December 2024

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30 Reads

The European Physical Journal C

The ATLAS tile calorimeter (TileCal) is the hadronic sampling calorimeter covering the central region of the ATLAS detector at the Large Hadron Collider (LHC). This paper gives an overview of the calorimeter’s operation and performance during the years 2015–2018 (Run 2). In this period, ATLAS collected proton–proton collision data at a centre-of-mass energy of 13 TeV and the TileCal was 99.65% efficient for data-taking. The signal reconstruction, the calibration procedures, and the detector operational status are presented. The performance of two ATLAS trigger systems making use of TileCal information, the minimum-bias trigger scintillators and the tile muon trigger, is discussed. Studies of radiation effects allow the degradation of the output signals at the end of the LHC and HL-LHC operations to be estimated. Finally, the TileCal response to isolated muons, hadrons and jets from proton–proton collisions is presented. The energy and time calibration methods performed excellently, resulting in good stability and uniformity of the calorimeter response during Run 2. The setting of the energy scale was performed with an uncertainty of 2%. The results demonstrate that the performance is in accordance with specifications defined in the Technical Design Report.


Measurement of the W-boson mass and width with the ATLAS detector using proton–proton collisions at s=7\sqrt{s}=7 TeV

December 2024

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30 Reads

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11 Citations

The European Physical Journal C

Proton–proton collision data recorded by the ATLAS detector in 2011, at a centre-of-mass energy of 7 TeV, have been used for an improved determination of the W -boson mass and a first measurement of the W -boson width at the LHC. Recent fits to the proton parton distribution functions are incorporated in the measurement procedure and an improved statistical method is used to increase the measurement precision. The measurement of the W -boson mass yields a value of mW=80,366.5±9.8 (stat.)±12.5 (syst.)m_W = 80{,}366.5 \pm 9.8~(\text {stat.}) \pm 12.5~(\text {syst.}) m W = 80 , 366.5 ± 9.8 ( stat. ) ± 12.5 ( syst. ) MeV =80,366.5±15.9= 80{,}366.5 \pm 15.9 = 80 , 366.5 ± 15.9 MeV, and the width is measured as ΓW=2202±32 (stat.)±34 (syst.)\Gamma _W = 2202 \pm 32~(\text {stat.}) \pm 34~(\text {syst.}) Γ W = 2202 ± 32 ( stat. ) ± 34 ( syst. ) MeV =2202±47= 2202 \pm 47 = 2202 ± 47 MeV. The first uncertainty components are statistical and the second correspond to the experimental and physics-modelling systematic uncertainties. Both results are consistent with the expectation from fits to electroweak precision data. The present measurement of mWm_W m W is compatible with and supersedes the previous measurement performed using the same data.


Citations (71)


... While the latest ttbb measurements by ATLAS and CMS [22,23] show similar trends in comparison with theory predictions, comparing of the results is not straight forward because of different final states and definitions of the fiducial phase space (see Fig. 3 for the ATLAS result). In addition to harmonized selections, common MC samples with similar generators and scale choices would be extremely useful in this context. ...

Reference:

TOP2024: an overview of experimental results
Measurement of tt t\overline{t} production in association with additional b-jets in the eμ final state in proton–proton collisions at s \sqrt{s} = 13 TeV with the ATLAS detector

Journal of High Energy Physics

... The acquired knowledge from multidifferential measurements went beyond understanding the top quark p T distributions and used to extract SM parameters such as α S and top quark mass, and to constrain the gluon density function of protons 3 . The state-ofthe-art ML methods have made it possible to perform simultaneous differential measurements of many more observables with a higher granularity in other physics processes [16,17]. It is desired to use the same techniques for differential σ tt measurements. ...

Simultaneous Unbinned Differential Cross-Section Measurement of Twenty-Four Z + jets Kinematic Observables with the ATLAS Detector

Physical Review Letters

... Within this volume, K S and Λ decays can be easily identified using their highly displaced vertices and the possibility to reconstruct the invariant mass of the two products, as long as the tracks are reconstructed (see, e.g., Refs. [49][50][51]). As mentioned above, we simulate the track reconstruction efficiency as a function of the track production radius based on Ref. [48]. ...

Underlying-event studies with strange hadrons in pp collisions at s=13\sqrt{s} = 13 TeV with the ATLAS detector

The European Physical Journal C

... The Standard Model has been tested to an exceptional degree of precision at the high-energy colliders and through various other experiments, establishing itself as the nature's theory for strong and electroweak (EW) interactions. The recent examples include the discovery of 125 GeV Higgs boson at the Large Hadron Collider (LHC) [1,2], and the remeasurement of the W-boson mass at the ATLAS [3] and CMS [4], where SM predictions closely match with the experimental data. However, despite all its excellence as a theoa e-mail: bibhabasude@gmail.com ...

Measurement of the W-boson mass and width with the ATLAS detector using proton–proton collisions at s=7\sqrt{s}=7 TeV

The European Physical Journal C

... Quantum fluctuations. -In realistic heavy-ion collisions, with respect to the mean transverse momentum and the charged particle multiplicity, the presence of fluctuations leads to a two-dimensional joint probability distribution of P(∆ p , ∆ N ) [30][31][32], instead of the deterministic relation Eq. (2). ...

Disentangling Sources of Momentum Fluctuations in Xe + Xe and Pb + Pb Collisions with the ATLAS Detector

Physical Review Letters

... In addition to harmonized selections, common MC samples with similar generators and scale choices would be extremely useful in this context. The CMS ttcc measurement has to be updated with the high-performance c-taggers, and in view of the latest ATLAS result [24]. The LHC searches for tttt have been concluded with the observation of the process in Run 2, 3 Refer to this presentation for a comprehensive overview. ...

Measurement of top-quark pair production in association with charm quarks in proton–proton collisions at s = 13 TeV with the ATLAS detector
  • Citing Article
  • December 2024

Physics Letters B

... Many searches for heavy neutral leptons (HNL) have been carried out or are ongoing at the LHC. The ATLAS analysis [15] discussed here uses a novel tt channel to search for HNL. One top quark decays according to the SM, while the other includes a t → N ℓ, N → W ℓ decay chain; this leads to LNV of two units. ...

Search for heavy right-handed Majorana neutrinos in the decay of top quarks produced in proton-proton collisions at s = 13 TeV with the ATLAS detector

Physical Review D

... In addition, CMS reported a measurements at s = 5.02 TeV [7], to compare with the corresponding ATLAS result [8] and to be used as a reference for top quark studies in heavy ion collisions at the same center-of-mass energy, E c.o.m . The ATLAS collaboration presented a σ tt measurements in proton-lead (pPb) collisions at s = 8.16 TeV [9] to compare with an earlier result by CMS [10]. New results from both experiments call for further discussions and comparisons of analysis details and simulation settings, which can be particularly interesting when heavy ions are involved. ...

Observation of tt t\overline{t} production in the lepton+jets and dilepton channels in p+Pb collisions at sNN \sqrt{s_{\textrm{NN}}} = 8.16 TeV with the ATLAS detector

Journal of High Energy Physics

... The other possible two-body decays e.g., into H ± H ± or H ± W ± are not kinematically allowed due to the small mass gap of m H ±± and m H ± . We have checked the consistency of the favored parameter space against the latest collider search results of doubly charged Higgs; produced via vector boson fusion (VBF) [128][129][130] or pair-produced via photon or Z-boson mediated diagrams [127]. They decay into W ± W ± in both cases. ...

Combination of searches for singly and doubly charged Higgs bosons produced via vector-boson fusion in proton–proton collisions at s = 13 TeV with the ATLAS detector
  • Citing Article
  • November 2024

Physics Letters B

... On the experimental side, the ATLAS collaboration published a first internal global SMEFT analysis to Higgs and EW data in Ref. [89], which is simultaneously sensitive to 28 operators and presents bounds at linear and quadratic order in the EFT expansion. It adopts the STXS 1.2 framework in the Higgs sector [90] and includes 5 Higgs-decay channels (ZZ, W W , γγ, bb, τ τ ) for all production modes, which was updated recently to include in addition the µµ and Zγ decay channels [91]. The EW data span LHC diboson differential measurements, four-lepton production (which includes leptonpairs produced via virtual photons), and Z-boson production in Vector Boson Fusion (VBF), as well as the the EW precision observables measured at LEP and SLD [92]. ...

Interpretations of the ATLAS measurements of Higgs boson production and decay rates and differential cross-sections in pp collisions at s \sqrt{s} = 13 TeV

Journal of High Energy Physics