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Autumn Institute II: Testing the Standard Model at low and high energies

Aim of the workshop: The Autumn Institute II will gather theorists and experimentalists, working mostly in the Rome area and at CERN in the field of collider physics. In an informal environment, we shall investigate a few selected topics on possible tests of the Standard Model at low and high energies. In particular, we will discuss open issues in the dark sectors (dark photons and dark matter), the prospects for Lepton Flavour Violation in the Mu2e experiment, tests of discrete symmetries, such as CP and CPT at KLOE, as well as the latest observations of top-pair production in association with Higgs bosons at the LHC. Speakers: Barbara Mele (INFN Roma) "Searching for a massless dark photon" Stefano Miscetti (INFN LNF) "Mu2e: The search for muon-to-electron conversion at Fermilab" Doojin Kim (CERN) "Searches for `Relativistic' Inelastic Dark Matter" Valentina Vecchio (Università di Roma 3) "Evidence for ttH production with the ATLAS detector" Antonio Di Domenico (Università di Roma `La Sapienza') "Test of discrete symmetries with neutral kaons at KLOE-2"

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Calculation of the critical temperature for Fermi superfluid throughout the BCS-BEC crossover.

The problem of the theoretical description of the critical temperature Tc of a Fermi superfluid dates back to the work of Gor’kov and Melik-Barkhudarov (GMB), who addressed it for a weakly-coupled (dilute) superfluid in what would today be referred to as the (extreme) BCS (weak-coupling) limit of the BCS-BEC crossover. The point made in this context by GMB was that particle-particle (pairing) excitations, which are responsible for superfluidity to occur below Tc, and particle-hole excitations, which give rise to screening also in a normal system, get e ectively disentangled from each other in the BCS limit, thus yielding a reduction by a factor 2:2 of the value of Tc obtained when neglecting screening e ects. Subsequent work on this topic, that was aimed at extending the original GMB argument away from the BCS limit, has tout court kept this disentangling between pairing and screening throughout the BCS-BEC crossover, without realising that the conditions for it to be valid are soon violated away from the BCS limit. Here, we reconsider this problem from a more general perspective and argue that pairing and screening are intrinsically entangled with each other along the whole BCS-BEC crossover but for the BCS limit considered by GMB, with the particle-hole excitations soon transmuting into particle-particle excitations away from this limit. We substantiate our argument by performing a detailed numerical calculation of the GMB diagrammatic contribution suitably extended to the whole BCS-BEC crossover, where the full wave-vector and frequency dependence occurring in the repeated two-particle in medium ...

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The challenge of the Heterogeneous Computing: the CMS case for 2020s

Starting from 2020, during LHC Run 3, the increased accelerator luminosity with the consequently increased number of simultaneous proton-proton collisions (pile-up) will pose significant new challenges for the CMS experiment. The primary goal of the HLT is to apply a specific set of physics selection algorithms and to accept the events with the most interesting physics content. To cope with the incoming event rate, the online reconstruction of a single event for the HLT has to be done within 220ms on average. The increasing complexity of events will make track reconstruction especially challenging. For this reason, reconstruction of Pixel Tracks is not executed for every event or is executed in ROIs.

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Studies of Baryon Resonances with the HADES Spectrometer and Pion Beams @ GSI

The HADES (High Acceptance DiElectron Spectrometer) detector, installed at GSI in Darmstadt, was designed to measure e+epairs (dielectrons) in the 13.5 AGeV energy range. The experimental program of HADES focuses on two main goals. The first one is to measure dielectron emission from a compressed baryonic matter formed in heavy ion collisions and investigate inmedium hadron properties. The second goal is to study dielectron production in elementary proton–proton (pp) and pion–proton (mp) collisions and learn about hadron electromagnetic structure. Both objectives are complementary in a sense that the understanding of the in-medium effects involves also investigations of the dielectron invariant mass spectra in elementary mp,pp reactions. The elementary collisions, especially those with pion beams, also offer a great opportunity to unambiguously fix the description of baryonic resonances and their coupling to the light vector mesons (rho/omega) which plays essential role for the inmedium modifications. Therefore, to understand resonances production mechanisms a systematic energy scan and high precision data are needed. In 2014 a large dataset of m-p scattering have been obtained at four pion beam momenta (0.656, 0.69, 0.748 and 0.8 GeV/c). The data have been included into the multichannel Partial Wave Analysis (PWA) developed by the BonnGatchina group. A combined PWA analysis of all available data provides better understanding of the vector mesonresonance couplings and their impact on the transition formfactors. Recently, a new model of dielectrons productions in the exclusive reaction m N->Ne+e- within an effective field theory approach was proposed. Experimental and theoretical investigations of the reaction ...

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Measuring propagation speed of Coulomb fields

In planetary systems, the problem arises whether gravity attracting the planets towards the central star has an instantaneous action or propagates with finite velocity. Laplace noticed that, if gravity propagated with finite velocity, planets motion would become unstable due to a torque originating from time lag of the gravitational interactions. Given that equations describing gravitational interaction are formally the same describing electrostatic interactions, we have performed an experiment meant to measure the time/space evolution of the electric field generated by a uniformly moving set of electrons. The results we obtain seem compatible with an electric field rigidly carried by the beam itself.

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The spin statistics theorem is generalized to show that a state obeys Fermi-Dirac statistics if and only if the state is invariant under the action of SL(n;C). Also a discussion of the experimental evidence and how the theorem relates to spin entanglement and special relativity will be presented.

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