Impact of the recent results by the CMS and ATLAS Collaborations at the CERN Large Hadron Collider on an effective Minimal Supersymmetric extension of the Standard Model
We discuss the impact for light neutralinos in an effective Minimal Supersymmetric extension of the Standard Model of the recent results presented by the CMS and ATLAS Collaborations at the CERN Large Hadron Collider for a search of supersymmetry in proton-proton collisions at a center-of-mass energy of 7 TeV with an integrated luminosity of 35 inverse pb. We find that, in the specific case of light neutralinos, efficiencies for the specific signature searched by ATLAS (jets+missing transverse energy and an isolated lepton) imply a lower sensitivity compared to CMS (which searches for jets +missing transverse energy). Focusing on the CMS bound, if squark soft masses of the three families are assumed to be degenerate, the combination of the ensuing constraint on squark and gluino masses with the experimental limit on the b to s + gamma decay imply a lower bound on the neutralino mass that can reach the value of 11.9 GeV, depending on the gluino mass. On the other hand, when the universality condition among squark soft parameters is relaxed, the lower bound on the neutralino mass is not constrained by the CMS measurement and then remains at the value 7.5 GeV derived in previous papers.
We study the cross sections for the inclusive production of $ψ(2S)$ and $X(3872)$ hadrons in $pp$ collisions at the LHC at two different center-of-mass energies and compare with experimental data obtained by the ATLAS, CMS, and LHCb collaborations.
These proceedings discuss results from recent searches for third generation SUSY particles by the ATLAS and CMS experiments at the LHC. Analyses performed with 8 TeV data probing direct pair production of bottom and top squarks are presented.
A brief summary of recent measurements of QCD jet production at the LHC, featuring results from ATLAS and CMS, is given. Results for heavy flavours are also shown.
Recent results in soft QCD at LHC by the ATLAS, CMS and TOTEM Collaborations are presented. Special focus is reserved to studies in diffractive and forward physics, and to the underlying event, with comparison with previous results and highlighting novel techniques.
We investigate the physics case for a dedicated trigger-level analysis for very low mass diphoton resonances at ATLAS and CMS and introduce a new photon isolation criterion. This greatly increases the acceptance for light particles at the expense of a somewhat larger Standard Model background. We show how such an analysis would likely yield new experimental coverage for axion-like particles for masses below 15 GeV, bridging the gap with the region covered by flavor factories.
Recent measurements performed by the ATLAS and CMS collaborations on the Run 2 dataset are testing QCD with unprecedented precision. The wealth of data, an ever-improving experimental understanding of jets and photons, and novel measurements of jet substructure enable an improved understanding.
Recent results on cross sections sensitive to the parton distribution functions (PDFs) within the proton from the ATLAS and CMS Collaborations are presented. The potential impact on the inclusion of these data in fits to the PDFs is discussed. Recent results from fits including the data from jet, or vector boson production from the ATLAS and CMS experiments are discussed.
The CMS and ATLAS collaborations searched for Dark Matter (DM) particles directly produced in pair. The searches are performed using the full LHC Run-I dataset recorded with the CMS and ATLAS detectors in proton-proton collisions at a center-of-mass energy of 8 TeV. Signatures considered include those yielding energetic jets and large missing transverse momentum as well as electroweak bosons and heavy flavour quarks plus missing transverse energy. No deviation from SM background expectation was found and exclusion limits on DM production cross section were set.
I summarize an extensive ATLAS and CMS electroweak physics program that involves a variety of single boson, diboson, triboson, and vector boson scattering measurements. The relevance of these studies to our understanding of the electroweak sector and electroweak symmetry breaking is emphasized. I describe the recent results and prospects for future measurements.
The LHC has delivered several fb-1 of data in spring and summer 2011, opening new windows of opportunity for discovering phenomena beyond the Standard Model. A summary of the searches conducted by the ATLAS and CMS experiments based on about 1 fb-1 of data is presented.
An overview of the searches for heavy resonances that decay to leptons or quarks is presented. The results are based on the data collected by the ATLAS and CMS experiments in proton-proton collisions at $\sqrt{s} = 13~\textrm{TeV}$, and include for the first time the entire LHC Run 2 data set.
The first search is reported for direct heffalon production, using 23.3/fb per experiment of delivered integrated luminosity of proton-proton collisions at rootS = 8TeV from the Large Hadron Collider. The data were recorded with the ATLAS and the CMS detectors. Each exotic composite is assumed to be stable on the detector lifetime (tau >> ns). A particularly striking signature is expected. No signal events are observed after event selection. The cross section for heffalon production is found to be less than 64ab at the 95% confidence level.
The Large Hadron Collider (LHC) was operated at a center-of-mass energy of $\sqrt{s}$ = 7 and 8TeV for proton-proton collisions in Run I. The CMS and ATLAS detectors both collected approximately 20 $fb^{-1}$ of 8TeV data in the data taking period. This large dataset collected at an unprecedented energy provides an ideal opportunity to search for new physics. In this paper, a selection of recent results from the ATLAS and CMS Collaborations concerning searches for exotic phenomena are presented. The signal models of these analyses contain heavy resonances, dark matter particles, and long-lived …
We present definite correlations between the CMS 5 \fb all-hadronic search employing the stransverse mass variable $M_{T2}$ and the ATLAS 5 \fb all-hadronic and multijet supersymmetry (SUSY) searches, suggesting the possibility that both the ATLAS and CMS experiments are already registering a faint but legitimate SUSY signal at the LHC. We isolate this prospective mutual productivity beyond the Standard Model in the framework of the supersymmetric No-Scale Flipped $SU$(5) grand unified theory, supplemented with extra vector-like matter (flippons). Evident overproduction is observed in three CM…
An overview of recent results in Higgs boson physics obtained with the ATLAS and CMS experiments at the Large Hadron Collider located at CERN, Geneva, is presented. The focus is on measurements of the properties of the recently discovered Higgs boson with a mass of about 125 GeV. A brief selection of results in searches for Higgs bosons beyond the Standard Model is given, and prospects of future Higgs boson measurements and searches at the LHC are discussed.
In the present paper, the ATLAS inclusive $W^{\pm}$ and $Z$ boson production data are analysed together with the CMS inclusive $W^{\pm}$ and $Z$ boson production data to investigate any possible tensions between the data sets and to determine the strange sea fraction, within the framework of a parton distribution function fit at next-to-next-to leading order in perturbative QCD.
ATLAS and CMS have provided hints for the existence of a Higgs-like particle with mass of about 144 GeV with production cross section into standard decay channels which is about 50% that of the standard model Higgs boson. We show that this 50% suppression is exactly what the mirror matter model predicts when the two scalar mass eigenstates, each required to be maximal admixtures of a standard and mirror-Higgs boson, are separated in mass by more than their decay widths but less than the experimental resolution. We discuss prospects for the future confirmation of this interesting hint for non-s…
We reexamine the shapes of the strange quark parton distribution functions (PDFs) of the proton by means of quantum chromodynamics (QCD) analysis of {\hera} deep inelastic scattering cross section measurement at DESY, and inclusive gauge boson production and $W$ boson production associated with a charm quark from LHC at CERN. We find that there is an overall agreement on the strange quark distributions obtained from CMS $W$ + charm and ATLAS $W/Z$ data at the parton momentum fraction range $x \lesssim 10^{-2}$. Meanwhile, there is also a strong tension between these data towards large $x$. We …
A glimpse into the most recent searches for Dark Matter at the LHC performed by the ATLAS and CMS collaborations is presented. The results covered in this document are all based on Run-2 proton-proton collision data recorded at $\sqrt{s}=13\text{ TeV}$ and corresponding to an integrated luminosity of just under 140 $\text{fb}^{-1}$
Recently the ATLAS and CMS collaborations announced the discovery of a higgs particle with a mass of $\sim 125$ GeV. The results are mildly consistent with the Standard Model Higgs boson. However, the combined data from these collaborations seem to point to an excess in the $h \rightarrow γγ$ channel. In this work we analyze under which conditions this excess may be plausibly explained within the reduced minimal 3-3-1 model, while being consistent with bb, WW, ZZ and $τ^+τ^-$ channels. Moreover, we derive the properties of the heavy neutral and the doubly charged scalars predicted by the model…
Recent ATLAS data significantly extend the exclusion limits for supersymmetric particles. We examine the impact of such data on global fits of the constrained minimal supersymmetric standard model (CMSSM) to indirect and cosmological data. We calculate the likelihood map of the ATLAS search, taking into account systematic errors on the signal and on the background. We validate our calculation against the ATLAS determinaton of 95% confidence level exclusion contours. A previous CMSSM global fit is then re-weighted by the likelihood map, which takes a bite at the high probability density region …
A concise review of precision measurements in the Higgs sector of the Standard Model (SM) of particle physics is given using ATLAS and CMS data. The results are based on LHC Run-2 data, taken between 2015 and 2018. Impressive progress has been made since the discovery of the Higgs boson in 2012 for measuring all major production and decay modes. Good agreement with the SM predictions was observed in all measurements.
Theoretical predictions for standard model (SM) processes involving top quarks, such as top quark-antiquark pair or single top production, depend on fundamental SM parameters like the strong coupling constant or the top quark mass. By confronting predictions with measurements performed at the ATLAS and CMS Collaboration using data collected at the CERN LHC in the second data taking period, these parameters can be determined precisely. In these proceedings, recent results measuring SM and top quark properties are presented.
Selected topics of the top-quark mass measurements in well-defined schemes are presented. The measurements have been performed using data recorded with the ATLAS and CMS detectors at the LHC at proton-proton centre-of-mass energies of 7 and 8 TeV. Precision theoretical QCD calculations for both inclusive top-antitop quark pair production and top-antitop quark pair production with an additional jet to extract the top quark mass in the pole-mass scheme have been used.
Searches for Higgs bosons in different extensions of the Standard Model (SM) are presented. These include the Minimal Supersymmetric extension of the SM (MSSM), the next-to-MSSM (NMSSM), models with additional scalar singlets, doublets, or triplets, and generic searches for models with couplings modified with respect to the SM or for non-SM Higgs boson decay channels. Results are based on data collected by the ATLAS and CMS experiments in 2011 and 2012 at the LHC. No excess is found in any of the searches and thus the resulting exclusion limits are given.
With the absence of the direct detection of new physics and the large data set collected at the LHC, the search for indirect effects in precision measurements became popular. Effective field theories enable to interpret these effects that originate from physics manifested at currently unreachable energy scales in a model independent framework. In this report, an overview of new analyses performed by the ATLAS and CMS Collaborations in the field of top quark physics is given.
Measurements of single top and rare top quark production may be sensitive to theories of physics beyond the standard model (SM), including those in which the energy scale of new physics is beyond the energies directly accessible at the Large Hadron Collider. Such models may be observable through signatures like forbidden SM interactions or deviations of the top quark's couplings from the SM predictions. An overview of recent searches from the ATLAS and CMS Collaborations is presented, with a focus on flavor-changing neutral currents.
This paper has been withdrawn by the authors in order to comply with the ATLAS publication policy and is now only available via the CERN cdsweb (http://cdsweb.cern.ch/record/984015)
We perform a detailed comparison of next-to-next-to-leading order (NNLO) QCD predictions for the W+jet and Z+jet processes with 7 TeV experimental data from ATLAS and CMS. We observe excellent agreement between theory and data for most studied observables, which span several orders of magnitude in both cross section and energy. For some observables, such as the $H_T$ distribution, the NNLO QCD corrections are essential for resolving existing discrepancies between theory and data.
Theoretical predictions of top-quark cross sections depend on the values of the parameters of the quantum chromodynamics Lagrangian, such as the strong coupling constant and the mass of the top quark, but also on parameters of the electroweak sector of the standard model and parton distribution functions. Comparisons between state-of-the-art calculations and recent measurements at the ATLAS and CMS experiments at the CERN LHC allow for the precise determination of these parameters. In this proceeding, the most recent results by the two collaborations are summarized and discussed.
We present persistently amassing evidence that the CMS and ATLAS Collaborations may indeed be already registering supersymmetry events at the Large Hadron Collider (LHC). Our analysis is performed in the context of a highly phenomenologically favorable model named No-Scale F-SU(5), which represents the unification of the F-lipped SU(5) Grand Unified Theory (GUT), two pairs of hypothetical TeV-scale vector-like supersymmetric multiplets derived out of F-Theory, and the dynamically established boundary conditions of No-Scale supergravity. We document highly suggestive correlations between the fi…
Polarization of strange quarks is preserved to a high degree when they hadronize into Lambda baryons, as observed in Z decays at LEP. This opens up the possibility for ATLAS and CMS to use strange-quark polarization measurements as a characterization tool for new physics scenarios that produce such quarks. Measurements in ttbar samples would be useful for obtaining additional information about the polarization transfer from the strange quark to the Lambda baryon. Already with 100/fb in Run 2, ttbar samples in ATLAS and CMS become competitive in sensitivity with the Z samples of the LEP experim…
The process $pp \to W^-c$ produces polarized charm quarks. The polarization is expected to be partly retained in $Λ_c$ baryons when those form in the $c$-quark hadronization. We argue that it will likely be possible for ATLAS and CMS to measure the $Λ_c$ polarization in the $W$+$c$ samples in Run 2 of the LHC. This can become the first measurement ever of a longitudinal polarization of charm quarks. Its results will provide a unique input to the understanding of polarization transfer in fragmentation. They will also allow applying the same measurement technique to other (e.g., new physics) sam…
Constraints on dark matter from the first CMS and ATLAS SUSY searches are investigated. It is shown that within the minimal supergravity model, the early search for supersymmetry at the LHC has depleted a large portion of the signature space in dark matter direct detection experiments. In particular, the prospects for detecting signals of dark matter in the XENON and CDMS experiments are significantly affected in the low neutralino mass region. Here the relic density of dark matter typically arises from slepton coannihilations in the early universe. In contrast, it is found that the CMS and AT…
Between the ATLAS and CMS collaborations at the LHC, hundreds of individual event selections have been measured in the data to look for evidence of supersymmetry at a center of mass energy of 8 TeV. While there is currently no significant evidence for any particular model of supersymmetry, the large number of searches should have produced some large statistical fluctuations. By analyzing the distribution of p-values from the various searches, we determine that the number of excesses is consistent with the Standard Model only hypothesis. However, we do find a shortage of signal regions with far…
The CMS and the ATLAS Collaborations have recently reported on the search for supersymmetry with 35 pb$^{-1}$ of data and have put independent limits on the parameter space of the supergravity unified model with universal boundary conditions at the GUT scale for soft breaking, i.e., the mSUGRA model. We extend this study by examining other regions of the mSUGRA parameter space in $A_0$ and $\tanβ$. Further, we contrast the reach of CMS and ATLAS with 35 pb$^{-1}$ of data with the indirect constraints, i.e., the constraints from the Higgs boson mass limits, from flavor physics and from the dark…
This report summarizes latest ATLAS and CMS results on Higgs boson couplings to fermions.~Presented topics include decays into final states of pairs of tau leptons and pairs of bottom quarks as well as results on the ttH production mode.~Results are complemented by tests of the CP invariance and searches for lepton flavor violating decays.~Finally, prospects of future Higgs boson analyses within the scope of the High Luminosity LHC program are discussed.~The presented results mostly use LHC 2016 data collected at a center-of-mass energy of $\sqrt{\mathrm{s}}=13~$TeV corresponding to an integra…
We consider the diphoton resonance at the 13 TeV LHC in a consistent model with new scalars and vector-like fermions added to the Standard Model (SM), which can be constructed from orbifold grand unified theories and string models. The gauge coupling unification can be achieved, neutrino masses can be generated radiatively, and electroweak vacuum stability problem can be solved. To explain the diphoton resonance, we study a spin-0 particle, and discuss various associated final states.
We discuss the possibility to study oscillations of atmospheric neutrinos in the ATLAS experiment at CERN. Due to the large total detector mass, a significant number of events is expected, and during the shutdown phases of the LHC, reconstruction of these events will be possible with very good energy and angular resolutions, and with charge identification. We argue that 500 live days of neutrino running could be achieved, and that a total of ~160 contained ν_μevents and ~360 upward going muons could be collected during this time. Despite the low statistics, the excellent detector resolution wi…
Measurements of $\mathrm{t\bar{t}}$ spin correlations are presented in events with top quarks produced in $\mathrm{pp}$ collisions at the LHC. The data correspond to an integrated luminosity of $36\:\mathrm{fb^{-1}}$ at $\sqrt{s}=13\:\mathrm{TeV}$ collected at both the ATLAS and CMS detectors. The spin correlations are measured using the angular distributions of the leptons in dilepton channel $\mathrm{t\bar{t}}$ events. The spin correlations are probed both directly, using distributions measured in the top quark rest frames that depend only on the top quark spin, and indirectly, using distrib…
Visible signals from the decays of light long-lived hidden sector particles have been extensively searched for at beam dump, fixed-target, and collider experiments. If such hidden sectors couple to the Standard Model through mediators heavier than $\sim 10$ GeV, their production at low-energy accelerators is kinematically suppressed, leaving open significant pockets of viable parameter space. We investigate this scenario in models of inelastic dark matter, which give rise to visible signals at various existing and proposed LHC experiments, such as ATLAS, CMS, LHCb, CODEX-b, FASER, and MATHUSLA…
Multifractal analysis was performed on $pp$ collision data at $\sqrt{s}=$ 0.9, 7 and 8 TeV from the CMS experiment at CERN. The data was obtained and processed from the CERN Open Data Portal. Vertical analysis was used to compute the generalised dimensions $D_q$ and the multifractal spectra $f(α)$ of the data, which reveals the level of complexity of its pseudorapidity distribution. It was found that the $f(α)$ curves widen with increasing collision energy, signalling an increase in branching complexity.
By applying the Error PDF Updating Method, we analyze the impact of the absolute and normalized single differential cross-sections for top-quark pair production data from the ATLAS and CMS experiments at the Large Hadron Collider, at a centre-of-mass energy of $\sqrt{s}= 8$ TeV, on the CT14HERA2 PDFs. We find that the top quark pair single differential distributions provide minor constraints on the CT14HERA2 gluon PDF when the nominal CT14HERA2 inclusive jet production data are included in the fit. Larger constraints on the gluon distribution are present when the jet data are removed (CT14HERA…
We discuss the implications of the recent constraints on the Higgs sector of the Minimal Supersymmetric extension of the Standard Model obtained by the ATLAS and CMS collaborations at the lHC with $\sqrt s=7$ TeV and 36 pb$^{-1}$ of data. The main production and detection channel that is relevant in these analyses is the gluon--gluon and bottom quark fusion mechanisms leading to neutral Higgs bosons which subsequently decay into tau lepton pairs, $gg, b\bar b \to Higgs \to τ^+τ^-$. In this note, we show that: i) the exclusion limits are in fact more general than indicated by the ATLAS and CMS …
We suggest a new possibility for ATLAS and CMS to explore the t-tbar forward-backward asymmetry measured at the Tevatron, by attempting to reconstruct t-tbar events, with one of the tops decaying semileptonically in the central region (|η| < 2.5) and the other decaying hadronically in the forward region (|η| > 2.5). For several models which give comparable Tevatron signals, we study the charge asymmetry at the LHC as a function of cuts on |η| and on the t-tbar invariant mass, m_{t-tbar}. We show that there is an interesting complementarity between cuts on |η| and m_{t-tbar} to suppress the dom…
We analyze the problem of correlating pp interaction data from the central detectors with a subevent measured in an independent system of leading proton detectors using FP420 as an example. FP420 is an R&D project conducted by a collaboration formed by members of ATLAS and CMS to investigate the possibility of detecting new physics in the central exclusive channel, PP -> P + X + P,where the central system X may be a single particle, for example a Standard Model Higgs boson. With standard LHC optics, the protons emerge from the beam at a distance of 420m from the Interaction Point, for M_X ~ 12…
The most recent results on searches in lepton plus jet final states motivated by different models beyond the standard model are presented, using pp collision data collected by the ATLAS and CMS detectors during Run I and Run II at the CERN LHC. Leptoquarks and heavy Majorana neutrinos that arise in the left-right model are looked for in the final states with two leptons and two jets (ll + jj; l = e; mu; tau ). Heavy Majorana neutrinos are further investigated by relying on a composite-fermion scenario, considering two leptons and one large-radius jet (ll + J; l = e, mu), and in the context of …
Being able to measure the polarization of quarks produced in various processes at the LHC would be of fundamental significance. Measuring the polarizations of quarks produced in new physics processes, once discovered, can provide crucial information about the new physics Lagrangian. In a series of recent papers, we have investigated how quark polarization measurements can be done in practice. The polarizations of heavy quarks (b and c) are expected to be largely preserved in the lightest baryons they hadronize into, the Lambda_b and Lambda_c, respectively. Furthermore, it is known experimental…
