Search for new phenomena in final states with b-jets and missing transverse momentum in $$ \sqrt{\mathrm{s}} $$ = 13 TeV pp collisions with the ATLAS detector

The results of a search for new phenomena in final states with b-jets and missing transverse momentum using 139 fb−1 of proton-proton data collected at a centre-of-mass energy $$ \sqrt{s} $$ s = 13 TeV by the ATLAS detector at the LHC are reported. The analysis targets final states produced by the decay of a pair-produced supersymmetric bottom squark into a bottom quark and a stable neutralino. The analysis also seeks evidence for models of pair production of dark matter particles produced through the decay of a generic scalar or pseudoscalar mediator state in association with a pair of bottom quarks, and models of pair production of scalar third-generation down-type leptoquarks. No significant excess of events over the Standard Model background expectation is observed in any of the signal regions considered by the analysis. Bottom squark masses below 1270 GeV are excluded at 95% confidence level if the neutralino is massless. In the case of nearly mass-degenerate bottom squarks and neutralinos, the use of dedicated secondary-vertex identification techniques permits the exclusion of bottom squarks with masses up to 660 GeV for mass splittings between the squark and the neutralino of 10 GeV. These limits extend substantially beyond the regions of parameter space excluded by similar ATLAS searches performed previously.

Trapped Proton Fluxes Estimation Inside the South Atlantic Anomaly Using the NASA AE9/AP9/SPM Radiation Models along the China Seismo-Electromagnetic Satellite Orbit

The radiation belts in the Earth’s magnetosphere pose a hazard to satellite systems and spacecraft missions (both manned and unmanned), heavily affecting payload design and resources, thus resulting in an impact on the overall mission performance and final costs. The NASA AE9/AP9/SPM radiation models for energetic electrons, protons, and plasma provide useful information on the near-Earth environment, but they are still incomplete as to some features and, for some energy ranges, their predictions are not based on a statistically sufficient sample of direct measurements. Therefore, it is of the upmost importance to provide new data and direct measurements to improve their output. In this work, the AP9 model is applied to the China Seismo-Electromagnetic Satellite (CSES-01) orbit to estimate the flux of energetic protons over the South Atlantic Anomaly during a short testing period of one day, 1 January 2021. Moreover, a preliminary comparison with proton data obtained from the High-Energy Particle Detector (HEPD) on board CSES-01 is carried out. This estimation will serve as the starting ground for a forthcoming complete data analysis, enabling extensive testing and validation of current theoretical and empirical models.

Discovery of the bound state of three gluons - odderon

The TOTEM collaboration at the Large Hadron Collider, together with the D0 collaboration at the Tevatron collider at Fermilab, have announced the discovery of the odderon – a bound state of three gluons that was predicted about 50 years ago. The result was presented at CERN on March 5 and follows the joint submission in December 2020 of a CERN and Fermilab preprints by TOTEM and D0 reporting this observation. States comprising several gluons are usually called “glueballs”, and are peculiar objects made only of the carriers of the strong force. The advent of quantum chromodynamics led theorists to predict the existence of the odderon, C-odd gluonic compound. Proving its existence in high-energy collisions at Tevatron and LHC has been a major experimental challenge. The work is based on a model-independent analysis of data at medium-range momentum transfer. The TOTEM and D0 teams compared proton-proton data (recorded at collision energies of 2.76, 7, 8, and 13 TeV and extrapolated to 1.96 TeV), with Tevatron proton-antiproton data measured at 1.96 TeV. In agreement with theoretical predictions, the proton-proton cross-section exhibits a deeper dip and stays below the proton-antiproton cross-section until the bump region, thus evidence of odderon was found.

The solar wind angular-momentum flux observed during Solar Orbiter's first orbit

<p>The Solar Orbiter mission is currently in its cruise phase, during which the spacecraft's in-situ instrumentation measures the solar wind and the electromagnetic fields at different heliocentric distances. </p><p>We evaluate the solar wind angular-momentum flux by combining proton data from the Solar Wind Analyser (SWA) Proton-Alpha Sensor (PAS) and magnetic-field data from the Magnetometer (MAG) instruments on board Solar Orbiter during its first orbit. This allows us to evaluate the angular momentum in the protons in addition to that stored in magnetic-field stresses, and compare these to previous observations from other spacecraft. We discuss the statistical properties of the angular-momentum flux and its dependence on solar-wind properties. </p><p>Our results largely agree with previous measurements of the solar wind’s angular-momentum flux in the inner heliosphere and demonstrate the potential for future detailed studies of large-scale properties of the solar wind with the data from Solar Orbiter.</p>

Implementation of the CMS-SUS-19-006 analysis in the MadAnalysis 5 framework (supersymmetry with large hadronic activity and missing transverse energy; 137 fb−1)

We present the MadAnalysis 5 implementation and validation of the analysis Search for supersymmetry in proton-proton collisions at 13 TeV in final states with jets and missing transverse momentum (CMS-SUS-19-006). The search targets signatures with at least two jets and large missing transverse momentum in the all-hadronic final state. The analyzed luminosity is 137 fb[Formula: see text], corresponding to the Run 2 proton-proton data set recorded by the CMS detector at 13 TeV. This implementation has been validated in a variety of simplified models, by comparing derived cut flow tables and histograms with information provided by the CMS collaboration, using event samples that we simulated for the purpose of this re-implementation study. The validation is found to reproduce the signal acceptance in most cases.

Impact of LHC vector boson production in heavy ion collisions on strange PDFs

The extraction of the strange quark parton distribution function (PDF) poses a long-standing puzzle. Measurements from neutrino-nucleus deep inelastic scattering (DIS) experiments suggest the strange quark is suppressed compared to the light sea quarks, while recent studies of $$W^\pm /Z$$ W ± / Z boson production at the LHC imply a larger strange component at small x values. As the parton flavor determination in the proton depends on nuclear corrections, e.g. from heavy-target DIS, LHC heavy ion measurements can provide a distinct perspective to help clarify this situation. In this investigation we extend the nCTEQ15 nPDFs to study the impact of the LHC proton-lead $$W^\pm /Z$$ W ± / Z production data on both the flavor differentiation and nuclear corrections. This complementary data set provides new insights on both the LHC $$W^\pm /Z$$ W ± / Z proton analyses and the neutrino-nucleus DIS data. We identify these new nPDFs as nCTEQ15WZ. Our calculations are performed using a new implementation of the nCTEQ code (nCTEQ++) based on C++ which enables us to easily interface to external programs such as HOPPET, APPLgrid and MCFM. Our results indicate that, as suggested by the proton data, the small x nuclear strange sea appears larger than previously expected, even when the normalization of the $$W^{\pm }/Z$$ W ± / Z data is accommodated in the fit. Extending the nCTEQ15 analysis to include LHC $$W^\pm /Z$$ W ± / Z data represents an important step as we advance toward the next generation of nPDFs.

Saturn’s ring current observed during Cassini’s Grand Finale

<p>The presence of a substantial azimuthal current sheet in Saturn’s magnetosphere was identified in Voyager and Pioneer magnetometer data.  Data from these spacecraft showed depressions in the strength of the field below that expected for the internal field of the planet alone.  This ring current was  modelled  as a simple axisymmetric current system by Connerney et al. [1980, 1983].  In this study we utilise the Connerney ring current model to look at the size, shape, current density and total current of Saturn’s ring current as observed during the Cassini proximal orbits.  We compare the variations in these parameters with the phases of the planetary period oscillations and with the occurrence of magnetospheric storms as determined from propagated solar wind data and LEMMS electron and proton data. Overall, we find that Saturn’s ring current is a dynamical environment which varies in size and magnitude due to  both  planetary period oscillations and solar-driven storms.  </p>

Energetic Solar Particle Access to the Near-Equatorial Inner Magnetosphere

<p>Solar proton events are comprised of energetic protons of solar and interplanetary origin. Such energetic particles are able to access the magnetosphere at various locations according to their cutoff rigidity. The specific properties of solar proton access are of great interest for space weather prediction purposes. Using Van Allen Probes/Relativistic Electron-Proton Telescope (REPT) 20-200 MeV proton data we examine four of the strongest solar proton events over the lifetime of the mission. We present evidence of the direct magnetospheric access of these energetic solar protons and find strong flux increases at L<4. Results indicate that small and sudden flux changes measured by ACE spacecraft sensors upstream of Earth are also seen in the near-equatorial inner magnetosphere. Using the East-West asymmetry of solar protons as a proxy for cutoffs we examine the highly dynamic cutoff rigidity. We find there is evidence for: (1) cutoff rigidity dependence on MLT; (2) suppressed cutoffs with rapid Dst changes; and (3) rapid evolution of cutoffs even during quiet magnetospheric conditions.</p>