ANNULLATO Seminario teorico: Matteo Lostaglio (Barcellona)
Machine Learning for BSM searches: A New Perspective
Machine Learning (ML) techniques are emerging as a competitive tool for
The partonic structure of the electron
Although the computation of a vast class of $e^+e^-$ cross sections
is fully doable in perturbative QED, the perturbative series is not
well behaved unless a mechanism is devised that allows one to take
into account, to all orders in the coupling constant, the effects
due to multiple emissions of photons and $e^+e^-$ pairs off the
incoming particles. I shall discuss one such mechanism, that has
a strict analogy with its counterpart in QCD and is based upon
the so-called Parton Distribution Functions (PDFs) of the electron
and the positron. I shall present recent results that have improved
the accuracy to which these PDFs are known.
Per partecipare: gruppo Teams Università di Genova numero 1npbr0h
(se si possiede un account Teams Unige, si può accedere con il codice.
Se invece si possiede solo un account Teams INFN, scrivere a
simone.marzani@ge.infn.it per essere aggiunti come ospiti).
POKER: POsitron resonant annihilation into darK mattER
Light dark matter is the new compelling hypothesis that identifies dark matter with new sub-GeV “Hidden Sector” states, neutral under Standard Model interactions and interfacing with our world through a new force. Accelerator-based searches at the intensity frontier are uniquely suited to explore it. However, current and planned efforts are either limited by the low sensitivity or the high backgrounds. This calls for a major breakthrough in the field.
The goal of POKER is to establish and demonstrate a new approach to search for light dark matter, based on a missing energy measurement with a positron-beam, active thick-target setup.
The new technique, based on light dark matter production through positron annihilation on atomic electrons, is characterized by a larger signal yield compared to previously explored reactions, and by a unique signal signature resulting from the underlying reaction dynamics: a peak in the missing energy distribution.
The final objective of the project, approved as a 1.5 M€ ERC Starting Grant for 2020-2025, is to perform a pilot run with the 100 GeV positron beam available at the H4 beamline at CERN, to demonstrate the technique by exploring a so-far unknown territory in the Hidden Sector parameters space.
In this seminar, after a brief introduction the Hidden Sector physics case, I’ll first discuss the potential of accelerator-based light dark matter efforts. I’ll then present the POKER experiment, focusing on the active thick target – the key element of the project. I’ll finally show the sensitivity of POKER to different Light Dark Matter scenarios.
Threshold resummation in rapidity distribution of a colourless particle production at the LHC
We demonstrate a detailed procedure to resum threshold-enhanced logarithms to all orders in perturbative QCD in the rapidity distribution of a system of non-QCD partons produced at the hadron colliders. The resummation procedure has been carried out in the double-Mellin space where the kinematics get factorized. As an immediate application of our formalism, we consider both Higgs boson production and a pair of leptons through Drell-Yan at the LHC to next-to-next-to-leading logarithmic accuracy matched to the corresponding fixed order results. We find that inclusion of these threshold logarithms through resummation procedure improves the reliability of perturbative predictions.
Per partecipare: gruppo Teams Università di Genova numero 1npbr0h
(se si possiede un account Teams Unige, si può accedere con il
codice.
Se invece si possiede solo un account Teams INFN, scrivere a
simone.marzani@ge.infn.it per essere aggiunti come ospiti).
‘Schwinger effect in superconductors’
From the sixties a deep connection has followed the development of superconductivity and quantum field theory. The Anderson-Higgs mechanism and the similarities between the Dirac and Bogoliubov-de Gennes equations are the most intriguing examples. In this last analogy, the massive Dirac particle is identified with a quasiparticle excitation and the fermion mass energy with the superconducting gap energy. I will show that, following this parallelism, it is possible to predict a new phenomenon: the superconducting Schwinger effect. As in the quantum electrodynamics Schwinger effect, where an electron-positron couple is created from the vacuum by an intense electric field, an electrostatic field can generate two coherent excitations from the superconducting ground-state condensate. These excitations are crucially different from the ones usually observed in superconductors and should lead to the weakening of the superconductivity.
I will discuss the connection with recent experiments and future developments inspired by the original Schwinger paper.
Per partecipare: gruppo Teams Università di Genova numero 1npbr0h (se si possiede un account Teams Unige, si può accedere con il codice.
Se invece si possiede solo un account Teams INFN, scrivere a simone.marzani@ge.infn.it per essere aggiunti come ospiti).
L’esperimento LUNA fa luce sulla densità della materia barionica
Nel silenzio cosmico dei Laboratori sotterranei del Gran Sasso, dove 1400 m di roccia proteggono le sale sperimentali dalle radiazioni esterne, l’esperimento LUNA è in grado di ricreare i processi che sono avvenuti durante la nucleosintesi primordiale (BBN) e che tutt’ora avvengono nelle stelle, e di riportare con il suo acceleratore di particelle l’orologio indietro nel tempo fino a pochi minuti dopo la nascita dell’universo.
L’abbondanza di deuterio primordiale dipende in maniera molto sensibile dalla densità di materia barionica. La misura della sezione d’urto della reazione D(p,gamma)3He effettuata con una precisione del 3% alle energie tipiche della BBN ha migliorato di molto la conoscenza del processo che distrugge il deuterio e ha migliorato la stima della sua abbondanza primordiale.
Nel seminario, dopo un’introduzione sull’esperimento LUNA che è operativo presso i laboratori del Gran Sasso da ormai 25 anni, sarà descritta questa nuova misura e le sue conseguenze per i modelli cosmologici. La densità di materia barionica ottenuta attraverso il risultato di LUNA è in buon accordo con il valore ricavato dallo studio della radiazione cosmica di fondo, il residuo “fossile” del big bang e fornisce supporto al modello cosmologico standard.
Sarà inoltre brevemente illustrata l’attività scientifica prevista nel prossimo decennio e basata sull’acquisizione di un nuovo acceleratore da 3.5 MV, LUNA-MV: nello specifico il progetto scientifico sarà focalizzato sullo studio di controversi processi decisivi nelle fasi di combustione dell’elio e del carbonio e che attendono da decenni una soluzione.
Sandra Zavatarelli is inviting you to a scheduled Zoom meeting.
Topic: LUNA p+d seminar
Time: Dec 1, 2020 02:30 PM Rome
Join Zoom Meeting
https://infn-it.zoom.us/j/85154678774?pwd=dXIxS1dnNnRLK0ZKV3YwdWQ3OEdYZz09
Meeting ID: 851 5467 8774
Passcode: 858083
‘Hydrodynamic electron transport’
In this talk I will review the progresses that has been done in the last year in the description of strongly coupled condensed matter electron systems by means of hydrodynamic and holographic effective field theories, focusing particularly on the experimental results. Particular attention will be put on recent results on high temperature superconductors. In the final part of the talk I will try to emphasize open questions and possible future directions.
Per partecipare: gruppo Teams Università di Genova numero 1npbr0h (se si possiede un account Teams Unige, si può accedere con il codice.
Se invece si possiede solo un account Teams INFN, scrivere a simone.marzani@ge.infn.it per essere aggiunti come ospiti).
Non-Fierz-Pauli Massive Gravity
Modifying gravity at large distances by means of a massive graviton may explain the observed acceleration of the Universe without Dark Energy. The standard paradigm for Massive Gravity is the Fierz-Pauli theory, which, nonetheless, displays well known flaws in its massless limit. The most serious one is represented by the vDVZ discontinuity, which consists in a disagreement between the massless limit of the Fierz-Pauli theory and General Relativity. A field-theoretical treatment of linearized Massive Gravity leads to an alternative theory describing the five degrees of freedom of the graviton, with a good massless limit, without vDVZ discontinuity, and depending on one mass parameter only, in agreement with the Fierz-Pauli theory.
Per partecipare: gruppo Teams Università di Genova numero 1npbr0h (se si possiede un account Teams Unige, si può accedere con il codice.
Se invece si possiede solo un account Teams INFN, scrivere a simone.marzani@ge.infn.it per essere aggiunti come ospiti).
Constraining the Minimal Dirac Gaugino Model
Most SUSY searches at the LHC are optimised for the MSSM, where gauginos are Majorana particles. By introducing Dirac gauginos, we obtain an enriched phenomenology, from which considerable differences in LHC signatures are expected. Concretely, in the Minimal Dirac Gaugino Model (MDGSSM) we have an electroweakino sector extended by two extra neutralino and one extra chargino eigenstates. Furthermore, a small mass splitting between the bino- like and between wino- like states can be naturally induced leading to the presence of Long Live Particles (LLPs). Here we discuss current limits on the gluinos and squarks and on the electroweakino sector of the MDGSSM, derived from reinterpretion LHC results and by considering constraints from dark matter searches. Finally, we discuss the presence of scenarios with LLPs whose predominant signature has not been covered in LHC searches.