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Sensitivity of a Gigahertz Fabry-Pérot Resonator for Axion Dark Matter Detection
No full textAxions are hypothetical pseudo-Nambu Goldstone bosons that could explain the observed cold dark matter density and solve the strong CP problem of quantum chromodynamics (QCD). Haloscope experiments commonly employ resonant cavities to search for a conversion of axion dark matter into photons in external magnetic fields. As the expected signal power degrades with increasing frequency, this approach becomes challenging at frequencies beyond tens of Gigahertz. Here, we propose a novel haloscope design based on an open Fabry-Pérot resonator. Operating a small-scale resonator at cryogenic temperatures and at modest magnetic fields should already lead to an unparalleled sensitivity for photon-axion couplings at 35GHz. We demonstrate how this sensitivity could be further improved using graded-phase mirrors and sketch possibilities to probe benchmark models of the QCD axion
Search for resonant production of pairs of dijet resonances through broad mediators in proton-proton collisions at = 13 TeV
No full textA reinterpretation of a prior narrow-resonance search is performed to investigate the resonant production of pairs of dijet resonances via broad mediators. This analysis targets events with four resolved jets, requiring dijet invariant masses greater than 0.2 TeV and four-jet invariant masses greater than 1.6 TeV. The search uses a data sample corresponding to an integrated luminosity of 138 fb collected by the CMS experiment in proton-proton collisions at = 13 TeV. The reinterpretation considers the production of new heavy four-jet resonances, with widths ranging from 1.5 to 10% of their mass, which decay to a pair of dijet resonances. This analysis probes resonant production in the four-jet and dijet mass distributions. Upper limits at 95% confidence level and significances are reported on the production cross section of new resonances as functions of their widths and masses, between 2 and 10 TeV. In particular, at a four-jet resonance mass of 8.6 TeV, the local (global) significance ranges from 3.9 (1.6) to 3.6 (1.4) standard deviations (s.d.) as the resonance width is increased from 1.5 to 10%. This relative insensitivity to the choice of width indicates that a broad resonance is an equally valid interpretation of this excess. The broad resonance hypothesis at a resonance mass of 8.6 TeV is supported by the presence of an event with a four-jet mass of 5.8 TeV and an average dijet mass of 2.0 TeV. Also, we report the reinterpretation of a second effect, at a four-jet resonance mass of 3.6 TeV, which has a local (global) significance of up to 3.9 (2.2) s.d
Search for medium effects using jet axis decorrelation in inclusive jets from PbPb collisions at = 5.02 TeV
No full textThe jet axis decorrelation in inclusive jets is studied using lead-lead (PbPb) collisions at a center-of-mass energy per nucleon pair of 5.02 TeV. The jet axis decorrelation is defined as the angular difference between two definitions of the jet axis. It is obtained by applying two recombination schemes on all the constituents of a given jet reconstructed by the anti-k sequential algorithm with a distance parameter of R = 0.4. The data set, corresponding to an integrated luminosity of 0.66 nb, was collected in 2018 with the CMS detector at the CERN LHC. The jet axis decorrelations are examined across collision centrality selections and intervals of jet transverse momentum. A centrality dependent evolution of the measured distributions is observed, with a progressive narrowing seen in more central events. This narrowing could result from medium-induced modification of the internal jet structure or reflect color charge effects in energy loss. This new measurement probes jet substructure in previously unexplored kinematic domains and show great promise for providing new insights on the color charge dependence of energy loss to jet-quenching models.[graphic not available: see fulltext
Evolution of soil organic matter pools during Martian regolith terraforming, with a focus on organo-Fe (oxyhydr)oxide interactions
No full textThe poor fertility of Martian regolith, due to its lack of organic matter (OM) and nitrogen (N), limits its suitability as a plant substrate. While compost amendment enhances short-term fertility, the mechanisms underlying long-term OM stabilization, particularly through interactions with iron (Fe) minerals, remain poorly understood. This study explores OM fractionation and Fe mineral transformations in Mojave Mars Simulant (MMS-1), both pure (R100) and amended with compost (R70C30), across two consecutive cropping cycles (potato followed by Vicia faba). Following Vicia faba cultivation, total C increased 12-fold in R70C30 (18.8 g kg) compared to R100 (1.6 g kg), with a 140 % increase in amended and 90 % in pure regolith relative to post-potato levels. Both particulate organic matter (POM) and mineral-associated organic matter (MAOM) also increased substantially: POM-C rose 7-fold, while MAOM-C increased by 947 %, suggesting the formation of organo-mineral complexes. MAOM also exhibited a 447 % rise in total N and the lowest C/N ratio (∼9), consistent with more microbially processed and stabilized OM.Fe speciation via Fe K-edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) revealed compost-driven enrichment of ferrihydrite and hematite, with distinct mineral profiles across POM and MAOM fractions. EXAFS further identified lepidocrocite and magnetite, phases undetected by XANES, highlighting the complementary role of reactive and crystalline Fe minerals in stabilizing OM in mineral matrices.These findings underscore the potential of organic amendments and leguminous crops to promote biologically functional, nutrient-rich substrates from Martian regolith simulants, offering critical insights for in situ resource utilization in space agriculture.
Thermal effects in conformal field theories
No full textConformal Field Theories (CFTs) are special classes of quantum field theories thatfind applications ranging from critical phenomena to theories of quantum gravity viaholography. Understanding thermal effects in CFTs is crucial: criticality is experimen-tally probed at finite temperature, and, from the holographic perspective, the studyof thermal CFTs is dual to the study of black holes in Anti-de Sitter space. In thisthesis, we explore the kinematics and dynamics of finite-temperature CFTs by analyz-ing broken and unbroken symmetries and adapting various analytical and numericalbootstrap approaches to finite-temperature correlation functions. These methods arenon-perturbatively valid and can be tested against exactly solvable models, such asfree theories and two-dimensional systems, as well as compared with perturbative cal-culations. The main applications discussed in this thesis concern one- and two-pointfunctions and the free energy density in the O(N) models in three dimensions, withparticular focus on the 3d Ising, XY, and Heisenberg models (N = 1,2,3)
Time resolved measurements of PdPt/AlO under CH oxidation conditions
No full textTime resolved HEGIXRD and HEGISAXS data of PdPt/AlO catalyst for full CH oxidation under operation. The measurements are recorded at 523K, 573K, 623K, 673K, and 723K with a reactor pressure of 100mbar, a total flow 100ml/min and a composition of 20% O2, 0.1% CH4, and 79.9% Ar
What the LHC tells us about the top quark, the heaviest particle in nature
No full textThe unprecedented data collected during proton-proton collisions at 13 and 13.6 TeV by the CERN LHC have significantly advanced our understanding of the top quark, the heaviest known elementary particle. This talk will highlight recent results on top quarks from the ATLAS and CMS collaborations, including precise determinations of key properties such as its mass and the production rates of rare processes, including four-top quark production. Additionally, the top quark's unique role in the Standard Model, particularly its large Yukawa coupling, close to unity, establishes a strong connection with the Higgs boson and makes it therefore a compelling focus for exploring potential new particles. Investigating top quark interactions at the highest energy scales underscores the potential of the LHC experiments to uncover fundamental new aspects of our universe
MaPSA quality control for the CMS phase-II detector upgrade
No full textThe Phase-II upgrade of the CMS detector aims to equip the outer tracker with new silicon sensor modules to handle the increased luminosity of the LHC. These modules integrate strip and pixel layers to enable precise position measurements, which will be placed in the inner layers of the outer tracker. The pixelated silicon sensor layer, paired with its readout chips, forms the macro-pixel sub-assembly (MaPSA). This presentation discusses the quality control procedures performed at DESY by the CMS Phase-II Tracker Upgrade group in Hamburg
Search for long-lived supersymmetric taus in CMS using BDT
No full textThe standard model is an effective theory but a low-energy approximation to a more complete theory. Supersymmetry (SUSY) extends the Standard Model but is expected to be broken and mediated to the visible sector via mechanisms like gravity or gauge mediation. In the search for beyond the standard model processes, we present an ongoing analysis based on simplified models to study the pair production and semileptonic decay of the hypothetical SUSY partner of the tau lepton, known as the stau (τ) within the CMS experiment at the CERN Large Hadron Collider (LHC). In gauge-mediated SUSY-breaking scenarios, the stau has macroscopic lifetime, and decays via τ → τχ01. This study focuses on events where one tau lepton decays to a muon, and the other decays hadronically, forming a jet. Using a dedicated machine learning algorithm for displaced tau tagging, we reconstruct the stau
Search for 3 top BSM resonances in boosted all hadronic final state
No full textThe production of three top quarks (3-top) has been identified as a promising signal for probing new physics beyond the Standard Model (BSM). Various BSM models propose a hypothetical Z’ boson that preferentially couples to top quarks, which could manifest as an enhanced 3-top signal, a scenario yet unexplored by the CMS experiment. Recent analyses by ATLAS and CMS indicate that the observed four and three top cross section fits are consistent with predictions of a three top production cross section exceeding that of the Standard Model (SM). This study explores two channels in the fully hadronic final state: tZ’ and tWZ’. Studies of three boosted top quark jets for Z’ masses in the TeV range and the search sensitivity of Run 2 and Run 3 will be reported