List of past RPMs — 2021
What is the nature of dark matter? What leads to the fundamental forces having such disparate strengths? Can we explain the small mass of the Higgs boson without excessive fine tuning? These outstanding questions are part of a broad motivation to continue investigating new physics scenarios beyond the Standard Model (SM). Several theoretical solutions propose an extended gauge symmetry group beyond the SM, and hence predict the existence of additional massive gauge bosons. I will discuss the latest search for a new neutral boson producing the particularly clean signature of two high energy leptons in the ATLAS detector.
In the second part of the talk I will share my ambitions for ongoing and future research in machine learning applications to particle physics, testing the SM in strategic connections to the Higgs boson, and work on the ATLAS Inner Tracker (ITk) upgrade.
Accelerator-based, long-baseline neutrino oscillation experiments are uniquely positioned to explore the CP-violating nature of the neutrino sector. This talk will briey discuss the experimental technique before surveying selected topics spanning both current and future generations of such experiments. First, the Bayesian Markov Chain Monte Carlo oscillation analysis of the T2K experiment, which has been accumulating data for the past 10 years, will be presented before discussing the ongoing efforts to extend the analysis framework to be used in a joint analysis between T2K and the NOA experiment at Fermilab. The experience obtained from these experiments already in the data taking stages has been and will continue to be invaluable in the design of future experiments, such as the Deep Underground Neutrino Experiment (DUNE). The DUNE collaboration will employ the liquid argon time projection chamber (LArTPC) technology at an unprecedented scale to measure neutrino interactions at its far site. The talk will conclude with an overview of the realization and operation of the protoDUNE-SP detector, a prototype for a DUNE far detector module, for a charged particle test beam run that took place at CERN in the end of 2018
The Higgs boson is the only fundamental spin-0 particle in the Standard Model (SM) of particle physics, associated with an ever-present field that is the source of mass and linked to electroweak symmetry breaking, making it a particle like no other. Its mass and spin provide us with the strongest indication yet that something is amiss with the SM, and offer a unique window to probe the SM and new physics in its decays. This talk covers a broad range of searches sensitive to new physics in the Higgs sector using the ATLAS detector at the CERN LHC, with an emphasis on the versatile role of novel machine learning techniques. The related physics prospects of the high-luminosity upgrade of the LHC and the ATLAS detector are also discussed.
The Belle II Experiment is a next generation SuperB factory that aims to discover new physics phenomena at the highest intensities. It started its first physics run in 2019 and will until the end of 2021 collect a data set comparable to what the previous B-Factory experiments recorded during a decade-long run. I will review the current status, point out the contributions my group is strongly involved in, and provide an outlook for the summer conferences 2021.
In the first part of my talk, I will briefly review the ways in which emission from galaxies and clusters can bias power spectra and cross-correlations of CMB lensing reconstructions, and describe our ongoing efforts to understand these biases analytically. Then, in the second part, I will explain how the lensing contamination to CMB B-modes can be removed what is known as delensing and discuss our recent findings regarding the performance of different delensing methods. I will also summarize preparatory work to delens SO data, and highlight biases to watch out for (and how to mitigate them) when the matter proxy used for delensing is either the cosmic infrared background or a lensing reconstruction derived from the CMB itself.
Hawking famously argued, based on semiclassical calculations, that the radiation from evaporating black holes is contains no information about the matter that fell in. This would be inconsistent with the unitarity of quantum mechanics. In this talk, I will show that, in more careful replica trick calculations, the gravitational path integral becomes dominated at late times by saddles containing spacetime wormholes. These wormholes cause the entropy to decrease after the Page time, consistent with unitarity, and allow information to escape from the interior of the black hole.
Events containing disappearing tracks originating from the decay of a heavy and electrically charged long-lived particle to a pair of undetectable particles are key to the discovery of compelling minimal dark matter models at collider experiments. This talk will present the prospects for a search for such experimental signature at a future muon collider. Techniques dedicated to the suppression of the backgrounds induced by the in-flight decays of the muon beams will be presented and the results compared to other future collider experiments in the context of MSSM higgsino and wino dark matter. In particular, this talk will show how a muon collider operating at a centre of mass energy of 10 TeV can rival, and in some cases outperform, the sensitivity of a 100 TeV proton proton collider.
?The high luminosity upgrade of the Large Hadron Collider (LHC), scheduled for 2025-2027, will significantly increase the instantaneous luminosity of the LHC collisions. The resulting large proton-proton collision datasets will allow precise measurements of Higgs? boson? properties, searches for ?very ?rare processes, and much more. To cope with the challenging ?experimental ?environment ?resulting ?from the high luminosity, significant upgrades will be required for the LHC ?detectors. A key upgrade of the CMS ?detector is to incorporate the identification of charged particle trajectories in the hardware-based trigger system, with potential to not only solidify the ?CMS ?trigger strategy but to enable ?searches for ??completely new physics ?signatures. This seminar will discuss the motivation of the CMS track trigger, give an overview of the system, and discuss its expected performance based on simulation? and hardware demonstration??.
The Forward Search Experiment (FASER) is the newest experiment at the LHC, approved in 2019 and recently installed into the CERN LHC complex. It is a small and inexpensive experiment placed 500 meters downstream of the ATLAS interaction point. FASER is designed to capture decays of exotic particles, produced in the very forward region, out of the ATLAS detector acceptance. In addition, FASERnu, a FASER sub-detector, is designed to detect collider neutrinos for the first time and study their properties. This seminar will present the physics prospects, the detector design, and the construction and installation progress of FASER.
The muon magnetic anomaly a_(?)?=?(g_(?)???2)/2 has been measured since 1959 at CERN, and the current 0.54 ppm precision world average has been published in 2006, using data collected at BNL in the years 1997-2001.
While the electron magnetic anomaly is measured and predicted with about three orders of magnitude better precision, the muon magnetic moment test of the Standard Model is more sensitive to hadronic effects and to most hypothetical New Physics contributions because the muon mass is about 200 times larger than the electron one. The sensitivity of the muon anomaly measurement extends to many New Physics effects that are searched in high energy experiments.
After a 3-years long analysis of data collected in 2018 at FNAL, the Muon g-2 collaboration has completed a measurement of the muon magnetic anomaly with a slightly improved precision of 0.46 ppm. The updated world average has a precision of 0.35 ppm and differs from the theory prediction by 4.2 standard deviations. We describe how the measurement has been performed by measuring the muon precession frequency is a storage ring and the magnetic field experienced by the muons and how the new world average has been computed. The precession frequency measurement dominates the uncertainty and has been completed by 6 independent groups with 4 different methods, obtaining consistent results. The data analysis has been performed in a blind way with a
special care for the internal consistency and the estimation of systematic biases and uncertainties.
The Muon g-2 collaboration aims at reducing the statistical uncertainty by a factor 2 in about 18 months from now, using data already collected, and eventually aims at collecting a total of about 20 times the statistics of the BNL data, to reach an ultimate precision of 0.14 ppm (0.10 statistical and 0.10 systematic).
It is time to start thinking about the next-next generation of colliders, that is, colliders that access the multi-10-TeV region of parton center of mass energies. The discussion has already begun with consideration of FCC-hh and muon colliders, but those technologies are not here yet, and there is room for additional proposals. One that is interesting to me is plasma wakefield acceleration of electrons and conversion to a gamma-gamma collider. In this talk, I will discuss possible schemes for this, and technical and physics questions for the proposal that need to be addressed.
We are having a special seminar followed by a panel discussion on the recent g-2 result for the muon, with an emphasis on the theoretical prediction for this quantity.
10:30am : Welcome
10:35am: Kálmán Szabó
11:05am: Martin Hoferichter
11:40am: Panel discussion + audience question/answer
Panelists: Gilberto Colangelo (chair), Aida El-Khadra, Christoph Lehner, Bill Marciano and Thomas Teubner
Theoretical predictions of the properties and dynamics of quantum many-body systems of importance to High-energy and nuclear physics research are anticipated to require, in many instances, beyond classical computational resources. Such systems may be amenable to quantum simulations in the future, and the very first steps are now being taken towards these objectives. I will discuss the potential and status of this newly emerging area, with a focus on field theories.
The LHCb experiment at the Large Hadron Collider (LHC) at CERN has been the world’s premier laboratory for studying processes in which the quark types (or flavors) change since 2011. Such processes are highly sensitive to quantum-mechanical contributions from as-yet-unknown particles, e.g. supersymmetric particles, even those that are too massive to produce at the LHC. I will discuss the status of these searches, including some intriguing anomalies. I will also present searches for the proposed dark matter analogs of the photon and the Higgs boson. Planned future upgrades and the resulting physics prospects will also be discussed, including our plans to process the full 5 terabytes per second of LHCb data in real time in the next LHC run.
The Jiangmen Underground Neutrino Observatory (JUNO) is a multi-purpose neutrino detector under construction in China. With a 20 kton neutrino target, and an energy resolution of 3% at 1 MeV, it will be the largest and most precise liquid scintillator detector ever constructed. By studying the disappearance of antineutrinos emitted from 8 nuclear reactors at a strategic baseline of about 53~km, JUNO will determine the neutrino mass ordering to ~3? significance within 6 years of running and will measure 3 neutrino oscillation parameters to sub-percent precision. JUNO will also study neutrinos from a variety of natural sources, such as the Earth, the Sun, and supernova explosions, and will deploy a satellite detector called JUNO-TAO that will measure the energy spectrum of reactor antineutrinos with unprecedented precision. The experiment is currently under construction, and completion is expected by 2022. JUNO’s physics prospects will be discussed in this talk alongside its ambitious design and current status.
On the theory side, LHC physics crucially relies on our ability to simulate events efficiently from first principles. In the coming LHC runs, these simulations will face unprecedented precision requirements to match the experimental accuracy. Innovative ML techniques like generative models can help us overcome limitations from the high dimensionality of the parameter space. Such networks can be employed within established simulation tools or as part of a new framework.
A summary of the latest results on the evidence of the four-top-quark production using proton-proton collision data at a centre of-mass energy of 13 TeV collected by the ATLAS detector at the Large Hadron Collider with an integrated luminosity of 139 fb?1. Events are selected if they contain a same-sign lepton (electron or a muon) pair or at least three leptons (2lSS/3l) or a single lepton or an opposite-sign lepton pair (1l/2lOS). A multivariate technique is used to discriminate between signal and background events in the signal rich regions.
The combined four top-quark production cross section is measured to be 24 +7/?6 fb, with a corresponding observed (expected) signal significance of 4.7 (2.6) standard deviations over the background-only
predictions. It is consistent within 2.0 standard deviations with the Standard Model expectation of 12.0 ± 2.4 fb.
Talk Recording Link:
Neutrinos are a tiny subatomic particle with surprising properties under active study. In particular, neutrinos oscillate, that is, they convert from one type of neutrino to another, is a surprising phenomenon under active study. The origin of neutrino mass is important for astrophysics, cosmology and particle physics, and many open questions surrounding neutrino oscillation exist. The Tokai-to-Kamioka (T2K) neutrino oscillation experiment sends a beam of muon flavor neutrinos or antineutrinos 295km across Japan. This seminar will discuss the state of the field of neutrino oscillation physics, including recent results from T2K, and T2Ks exciting future program.
I will review the Quantum Computing efforts in the Physics division, with the goal of allowing to calculate important properties of the Standard Model non-perturbatively and ultimately to simulate scattering at colliders from first principles. I will present several results, both on physics simulations and on noise mitigation, which is crucial to obtain results on near-term devices.
Measurements of the universe’s present-day expansion rate, or the Hubble constant (H0), that use a Cepheid variable star calibration of Type Ia supernovae (SNe Ia) are in >4? disagreement with values predicted by the standard, Lambda cold dark matter (LCDM) model of the universe. In this talk, I will review the evidence for this Hubble Tension and discuss in particular my work on an alternative calibration of the SNe Ia using the Tip of the Red Giant Branch (TRGB), a standard candle that can return distances precise to 2% when observed in ancient populations of stars. Anchored by the TRGB, we derived in the Carnegie Chicago Hubble Program a SN value of H0 that is significantly less in tension with base LCDM (<2?) than the Cepheid-calibrated SN H0, which raises the question of underestimated uncertainties and softens evidence for new physics. I will identify likely causes of this Cepheid-TRGB divergence, present paths to a potential resolution, and highlight how the astrophysical distance scale can converge on a self-consistent, 1% determ
The existence of long-lived particles (LLPs) is a common feature in many theories beyond the Standard Model. For example, models with small couplings (i.e. R-parity-violating supersymmetry) and models with compressed mass spectra (i.e. co-annihilating dark matter) predict the presence of LLPs. With lifetimes ranging from picoseconds to nanoseconds, massive LLPs could decay to several electrically charged particles in the inner tracking volume of the ATLAS detector, resulting in the reconstruction of a displaced secondary vertex. Integrating tracking information into the trigger at an early stage is critical to enhancing the sensitivity of future searches for LLPs with displaced track signatures. The ATLAS Fast TracKer (FTK) aimed to achieve this by performing global, hardware-based track finding at a trigger rate of 100 kHz.
In this talk, searches for new long-lived massive particles leaving a displaced vertex signature in the ATLAS inner detector with the full Run-2 dataset are presented. Furthermore, the FTK system is presented and its application to LLP searches is discussed.
This seminar will present recent results of a search for long-lived heavy neutral leptons (HNLs) in proton-protoncollisions at the Large Hadron Collider (LHC). The Standard Model (SM) of particle physics is an extremely successful theory and its major predictions have been precisely confirmed. However, the existence of neutrinos, with small nonzero masses, provides evidence that the SM is incomplete. Introducing HNLs into the SM is a natural wayto generate the light neutrino masses through a seesaw mechanism. This search uses 139 fb -1 of ATLAS experimental data collected between 2015 and 2018 at a centre-of-mass energy of 13 TeV. A non-standard techniqueis used to search for a displaced vertex from particle trajectories produced in the HNL decay to leptons. The dominant background from uncorrelated leptons crossing in the ATLAS detector is estimated using an objectshuffling method. The reconstructed HNL mass is used to discriminate between signal and background. No excessof events is observed and constraints on the strength of the interactions between HNLs and neutrinos are imposed in various scenarios.
This seminar will conclude with a presentation of methods used to study the detector performance and readout system of the ATLAS Inner Tracker (ITk). The LHC is currently undergoing upgrades that will enable it to produce more than ten times the data that has already been collected. To meet the requirements of this challenging new environment, an all-silicon particle tracking system will be installed in ATLAS.
Quantum fluctuations in inflation provide the seeds for the large scale distribution of matter today. According to the standard paradigm, these fluctuations induce density perturbations that are Gaussian distributed. In this limit, all the information is contained within the pairwise distribution of galaxies, usually represented by a power spectrum. Today, the distribution of matter is far from Gaussian, with structures forming across a vast range of scales. To date, almost all spectroscopic analyses have used only the two-point function. This begs the question: can we extract more information using higher-point statistics?
As the most recently-discovered particle of the Standard Model (SM), the Higgs boson plays a key role in the quest to deepen our understanding of fundamental physics. Measurements of its production cross-sections probe for disagreement with the SM that might hint at signs of new physics. I will present recent measurements of gluon fusion (ggF) and vector boson fusion (VBF) Higgs production in the H->WW*->evuv decay channel, using data from the ATLAS detector at CERNs Large Hadron Collider (LHC). These measurements are challenging due to the high-background environment, where on average fewer than one in one billion proton-proton collisions produces Higgs bosons. I will discuss novel analysis techniques and improvements that allow the first observation of the H->WW* process in the VBF channel and precise measurements of Higgs boson cross-sections in important kinematic regions. As preparations for the next LHC runs continue, I will lay out further ways in which the current and future LHC datasets can be exploited to creatively test the SM through Higgs physics.
Over the next few years, cutting-edge cosmological experiments such as DESI, Rubin and CMB-S4 will provide an exquisite probe of the accelerated expansion of the Universe, structure formation, and general relativity, and thus bring us closer to revealing the nature of dark energy, dark matter, inflation and neutrinos. One of the most critical issues with these experiments will be the connection between observed galaxies and the underlying matter field. My research program offers a viable path for constructing accurate models of the galaxy-matter connection and applying them to observational analysis, with the goal of recovering the missing pieces of our cosmological model. In particular, I will share my contributions to the development of state-of-the-art cosmological simulations and analysis tools and propose readily reachable goals for extracting cosmological information from the ongoing DESI and CMB experiments. Future breakthroughs will likely be the product of collaborative efforts across all of cosmology, galaxy formation and particle physics. My broad-scaled research proposal will bring together diverse ideas and aid LBNL science goals at the crossroads of cosmological discovery.
With the discovery of the Higgs boson in 2012, high energy physics has entered an era in which all fundamental particles predicted by the Standard Model have been observed. With no conclusive observations of physics beyond the Standard Model, precision tests of the properties of the Higgs boson are key to find indications of new physics. I will discuss the program of precision measurements of the Higgs Yukawa coupling strengths with the ATLAS experiment, focusing on those of the muon and top quark. I will give an overview of the search for Higgs decays in the dimuon channel with an emphasis on the novel use of quark/gluon tagging in an ATLAS Higgs measurement. Secondly, I will present the status and outlook for the joint measurement of ttW and ttH production in multi-lepton final states with an emphasis on ttW modeling, fake lepton estimation, and profile-likelihood unfolding. Finally, I will discuss the importance of the High Luminosity LHC for these physics goals in terms of sensitivity projections and the extension of tracking instrumentation provided by the ATLAS ITk upgrade.
The observation of a Higgs boson with a mass of about 125 GeV confirmed the nature of the electroweak symmetry breaking (EWSB) predicted by the standard model of particle physics, establishing that the W and Z gauge bosons acquire their mass via the Higgs mechanism. However, the discovered Higgs boson might not be the lone player responsible for EWSB. Further insights into the Higgs and the gauge bosons mutual- and self-couplings can be obtained from measurements of vector boson scattering (VBS) processes.
In this talk, I will present the study of same-sign WW, WZ, and ZZ boson pair productions in association with two jets with data collected by the CMS detector. The effort led to the most precise measurement of the EW same-sign WW cross section to date and the first experimental observation of the EW WZ production. It also formed the basis for the first measurements of the polarized VBS. Interpretations beyond the standard model, including the constraints on the structure of quartic vector boson interactions in the framework of effective field theory, will also be discussed.
The coupling of the Higgsboson to charm quarks has eluded experimental observation since the Higgs boson discovery in 2012. At present, this is the largest contribution to possibleHiggs boson decays that is not experimentally verified. However, this measurement is crucial to shed light on the fundamental coupling of the Higgs boson to second-generation quarks. This seminar highlights the recent search for Higgs boson decays into a pair of charm quarks, produced in association with a vector boson, using the data collected by the ATLAS detector between 2015 and 2018.This measurement sets the first direct limit on the Higgs boson coupling to charm quarks
With the upgrade to High-Luminosity LHC (HL-LHC), a significant improvement to this measurement is expected due to the increased size of the dataset as well as the upgrade of the ATLAS Inner Tracker (ITk). A new pixel detector system will improve resolution, increasing the identification efficiency of charm quarks. However, the detector will have to cope with higher data rates and withstand higher levels of radiation. The ITk pixel upgrade, particularly the characterisation of the pixel readout chips, and the expected precision of the measurement of the Higgs boson coupling to charm quarks at the HL-LHC are discussed.
Dark matter is one of the primary unsolved problems in modern particle physics. Since the late 1980s, physicists have been trying to directly detect dark matter particles passing through the Earth, typically by searching for nuclear recoils. This search has been unsuccessful so far, but I will discuss recent advancements and upcoming technologies that offer a promising path forward. First, I will present xenon time projection chambers, including the LUX and LUX-ZEPLIN experiments, as the best strategy for detecting Weakly Interacting Massive Particles (WIMPs). I will explain how understanding energy deposition in liquid xenon allows us to test the remaining WIMP parameter space, and I will discuss recent data-driven and simulation-driven advancements in this field. Second, I will discuss calorimetry as a tool for probing dark matter models below the WIMP scale, with masses on the order of 1-1000 MeV/c2. I will describe the TESSERACT project, using transition-edge sensors to achieve unprecedented sensitivity to a variety of dark matter interactions.
Despite overwhelming evidence of abundant dark matter in the Universe, the nature of this material remains a mystery. The General Antiparticle Spectrometer (GAPS) is an upcoming NASA Antarctic balloon mission to search for signatures of dark matter annihilation or decay in the fluxes of low-energy (<0.25 GeV/n) cosmic antinuclei. GAPS will produce a precision cosmic antiproton spectrum extending to an unexplored low-energy regime, with sensitivity to light dark matter models, primordial black holes, and cosmic-ray propagation. GAPS will also either provide the first unambiguous detection of a cosmic-ray antideuteron or exclude the viable dark matter models that predict a low-energy antideuteron flux orders of magnitude above the astrophysical background. To identify these rare low-energy antinuclei while rejecting the abundant positive- nucleus backgrounds, GAPS pioneers a novel exotic atom-based particle identification technique, which relies on a system of >10 m2 of large-area high-temperature lithium-drifted silicon (Si(Li)) detectors. I will discuss the GAPS science program, with a special emphasis on the exotic atom method of particle identification and the Si(Li) detectors that are central to its success.
Neutrinos exist in one of three types or flavors (?e ,?µ or ?? ), which oscillate from one to another when propagating through space. This phenomenon is one of the few that cannot be described using the Standard Model of particle physics and its study can thus provide new insight into the nature of our universe. As neutrinos interact only via the weak force, they are experimentally detected only following their interactions with atomic nuclei. Our understanding of such interactions is crucial for measuring neutrino oscillations. In this talk I will review key open questions in the study of neutrino oscillations that drive the need for improved understanding of neutrino-nucleus interactions. I will then present our studies of such interactions using both neutrino and electron beams with the MicroBooNE and CLAS detectors and their impact on next-generation high-precision neutrino oscillation measurements with the DUNE and Hyper-Kamiokande experiments.