Spaatind 2020 - Nordic conference on Particle Physics

2 Jan 2020, 14:00 → 7 Jan 2020, 12:00 Europe/Copenhagen

Thon Hotel (Skeikampen)

The 26th Nordic Particle Physics Meeting (Spaatind 2020) will take place at the THON Hotel in Skeikampen (Norway), from Thursday, January 2 to Tuesday, January 7, 2020.

The program includes lectures and overview presentations on some of the most actual topics in particle and astroparticle physics.
In addition, there are contributed talks presented by the participants.

Deadline for registration : November 24th

Invited Speakers

Marumi Kado (Sapienza Universita e INFN, Roma) - High  Luminosity LHC: Physics opportunities and experimental challenges

Marcella Bona (QMRHL) - Heavy Flavour physics

Torsten Bringmann (Oslo University) - Dark matter searches

Oleg Ruchayskiy (Niels Bohr Institute) - Searches for feebly interacting particles

Francesca Di Lodovico (Kings College, London) - Neutrino experiments

Michelangelo Mangano (CERN) - The Future Circular Collider

Mogens Dam (Niels Bohr Institute) - The European Strategy view

Rickard Ström (DESY) – The Compact Linear Collider

Alex B Nielsen (University of Stavanger) - Gravitational waves

Organizers

P.Hansen, M.Dam, S.Xella (NBI, subatomic group)

P.H.Damgaard (NBIA)

Thursday, 2 January

14:00 → 19:00 Arrival at Gardamoen, transfer to Thon Hotel

19:00 → 20:00 Dinner at Thon Hotel

Friday, 3 January

08:30 → 10:00 invited talks

08:30 HL-LHC : Physics opportunities and expertimental challenges (I)

Speaker: Marumi Kado (University of Roma 1, Sapienza, INFN Roma and LAL Orsay)

NordicHEP-1.pdf

09:15 Feebly interacting particles

Speaker: Dr Oleg Ruchayskiy (Niels Bohr Institute)

FIP_Ruchayskiy_Spaatind.pdf

15:00 → 16:30 invited talks

15:00 HL-LHC: Physics opportunities and experimental challenges (II)

Speaker: Marumi Kado (University of Roma 1, Sapienza, INFN Roma and LAL Orsay)

NordicHEP-2.pdf

15:45 Gravitational waves (I)

Speaker: Alex Nielsen (University of Stavanger)

Skeikampen1Jan2020.pdf

17:00 → 19:00 submitted talks

17:00 Releasing 13 TeV Open Data from the ATLAS experiment

During 2019 the second release of ATLAS Open Data for educational purposes has been prepared. This release consists of 10 fb$^{-1}$ of $\sqrt{s}$ = 13 TeV data from the ATLAS experiment, along with an extensive set of Monte Carlo simulated samples. In addition to the data, we also release various computing tools, with the aim of making analysis of the dataset more accessible to students. These tools include software frameworks in C++ and python, Jupyter notebooks and Virtual Machines. A wide range of analysis examples, which are meant as starting points for further analysis, have also been prepared. In this talk we give an overview of the dataset and the tools that are being released, as well as some examples of analyses that can be done with the dataset.

Speaker: Even Simonsen Haaland (University of Oslo (UiO))

ATLASOpenDataSpaatindEvenHaaland.pdf

17:20 Analytical reinterpretation of ATLAS dark matter mediator searches with final-state jets

An important part of the ATLAS dark matter (DM) search programme is comprised of searches for new resonances (dark matter mediators) decaying to hadronic final states. This talk will give an overview of one such analysis: the recently-published search for low-mass dark-matter mediators decaying to jets, with an associated high-pT photon. This search triggers on an associated photon in order to significantly extend the sensitive region of ATLAS for dark matter mediators and generic resonances. In particular, we cover an new method of reinterpretation of the resulting limits in the case of non-discovery to other model spaces.

Speaker: Eric Edward Corrigan

disr_AV.gif

disr_V.gif

SpaatindARcorrigan.pdf

17:40 Searches for charged Higgs bosons at CMS

An overview of the latest results on 13 TeV searches for a charged Higgs boson (H+) with the CMS experiment is presented. Different H+ production mechanisms and several final states are covered, focusing mostly on the H+ -> tau nu and H+ -> tb channels, which are especially interesting in the framework of Type-II two-Higgs-doublet-models including the MSSM. The first CMS results in the H+ mass range close to the top quark mass, as well as the first CMS search targeting the fully hadronic final state of the H+ -> tb channel, are covered. For each channel, the main experimental challenges and the analysis strategies chosen to overcome them are described. Model-independent limits on the H+ production rate, as obtained from these searches, are presented and interpreted in the context of the MSSM. To conclude, future prospects for the H+ searches with CMS are shortly discussed.

Speaker: Santeri Laurila

Santeri_Laurila_Spaatind2020.pdf

18:00 IceCube - Particle Physics and Astrophysics on Ice

Buried beneath the South Pole is the world's largest instrumented neutrino detector; IceCube. Inside of IceCube is the DeepCore sub-array, which is a densely instrumented inner region allowing analyses of neutrinos in the ~5-150 GeV energy range. In this talk I will cover some of the recent neutrino oscillations results, such as world-leading measurments of tau neutrino appearance, as well as a sub-TeV search for astrophysical neutrino sources. I will also discuss the scientific prospects of the IceCube Upgrade, a further low-energy extension to IceCube which will be deployed in 2022/23 and provide much needed measurements regarding the status of the 3-neutrino paradigm.

Speaker: D. Jason Koskinen (niels bohr institute)

Koskinen_IceCube_Spaatind_2020.pdf

18:20 Search for new resonances decaying into a top-anti-top pair with the ATLAS detector

A search for ttbar resonances in the fully hadronic final states is performed using data collected at √s = 13 TeV in 2015-2018, requiring the hadronically decaying top-quarks to be identified using large-radius jets with jet substructure information and associated smaller radius jets identified as originating from b-quarks. The analysis aims to improve the search sensitivity at high mass by exploiting advanced techniques on the top- and b-quark identification as well as the background estimate directly performed from data by fitting with a smoothly falling function.

Speaker: Trine Poulsen (Lund University)

ttbar_TrinePoulsen_Spåtind2020.pdf

18:40 Search for a Dark Jet Resonances Using Substructure with ATLAS

The possibility of dark matter being a composite particle, such as a hadron under a gauge group, is becoming increasingly appealing as the non-excluded part of parameter space for the WIMP paradigm is shrinking. In this talk I will present a ongoing search for a resonance originating from a QCD-like dark sector, that decays to two dark partons which then hadronise to form ”dark jets”. The search targets a selection of model parameters where a fraction of the dark mesons are stable and the rest decay promptly to visible particle. The signature is a pair of jets with potentially different substructure than normal QCD-jets. I will introduce the model and the initial signal studies that have been made on MC simulations and then go into more detail with the mass-decorrelated tagger implemented for the signal region definition.

Speaker: Eva Hansen (University of Lund)

EvaHansen_DarkJets_Spaatind2020.pdf

20:30 → 21:30 submitted talks

20:30 Dirac vs. Majorana HNLs (and their oscillations) at SHiP

SHiP is a proposed high-intensity beam dump experiment set to operate at the CERN SPS. It is expected to have an unprecedented sensitivity to a variety of models containing feebly-interacting particles, such as Heavy Neutral Leptons (HNLs). Two HNLs or more could successfully explain the observed neutrino masses through the seesaw mechanism. If, in addition, they are quasi-degenerate, they could be responsible for the baryon asymmetry of the Universe. Depending on their mass splitting, HNLs can have very different phenomenologies, e.g. they can behave either as Dirac or Majorana fermions. In this work, we consider the possibility of distinguishing Dirac and Majorana HNLs at SHiP. This requires being able to discriminate between lepton number conserving and violating decays in a beam dump setting. We show, both analytically and numerically, that this can be achieved by looking at the angular distribution of the visible HNL decay products. SHiP will thus be able to tell apart Dirac from Majorana HNLs in a significant region of parameter space, unconstrained by current or upcoming experiments. Even better, it may be able to resolve their coherent oscillations, hence providing a direct measurement of the mass splitting!

Speaker: Jean-Loup Tastet (Niels Bohr Institute)

JLTastet_Spaatind.pdf

20:50 Rethinking searches for new physics at the LHC

Searching for new physics phenomena in the energy frontier is one of the main goals of the Large Hadron Collider (LHC). The Standard Model of Particle Physics (SM) leaves outstanding questions which can be explored by colliders. Hundreds of searches for new physics have been performed since the LHC inception, but there is no definitive evidence for physics beyond the SM so far.
In recent years, Machine Learning (ML) techniques involving deep learning have successfully addressed tasks involving image recognition and text analysis, giving way to automatisation of complex tasks. Such methods have the potential to revolutionise how high energy physics analyses are made.
This talk reviews recent proposals on how to remodel searches for new physics at the LHC, by switching from hypothesis testing of a specific Beyond the Standard Model (BSM) scenario to the falsification of the SM in specific phase spaces. The deployment of ML techniques, particularly unsupervised algorithms, allows for searches of BSM processes without prior expectations or theory prejudice, potentially extending the scientific reach of the LHC.

Speaker: Flavia de Almeida Dias (University of Copenhagen)

FDias_Spaating2020.pdf

21:10 QCD at the high-energy frontier

When probed in very high energy collisions hadrons and nuclei are dense gluonic systems. The nonlinear interactions between these gluons can be understood with the color glass condensate effective theory that describes them as a classical color field. This talk will discuss recent advances in using this theoretical framework for scattering processes where the gluon field is probed with a dilute probe. Such processes include proton-nucleus collisions, exclusive photon-mediated interactions in nucleus-nucleus collisions and both inclusive and exclusive deep inelastic scattering. These processes are studied experimentally at the LHC and in future DIS experiments such as the EIC. The most natural way to describe them in the nonlinear high energy limit is a ``dipole'' picture where the dilute perturbative probe is quantized in light cone perturbation theory.

Speaker: Tuomas Lappi (University of Jyväskylä)

spaatind20.pdf

Saturday, 4 January

08:30 → 10:00 invited talks

08:30 Neutrino experiments(I)

Speaker: Francesca Di Lodovico (King's College London)

neutrinos1.pdf

09:15 gravitational waves (II)

Speaker: Alex Nielsen (MPI Hannover)

Skeikampen2Jan2020.pdf

15:00 → 16:30 invited talks

15:00 Neutrino experiments (II)

Speaker: Francesca Di Lodovico (King's College London)

neutrinos2.pdf

15:45 Discovery potential in flavour physics

Speaker: Marcella Bona (Queen Mary University of London (QMUL))

bona-spaatind2020.pdf

17:00 → 19:00 submitted talks

17:00 Hadrons in gravitational field, shear forces and viscosity in relativistic Heavy Ion collisions

Speaker: Oleg Teryaev (JINR, Dubna)

teryaev0401.pdf

17:20 The HIBEAM/NNbar Experiment

The existence of baryon number violating processes is a necessary condition to explain matter-antimatter asymmetry and may also play a role in accessing a hidden sector and addressing the question of dark matter. The construction of the European Spallation Source (ESS) provides a unique opportunity to exploit a high intensity beam of cold neutrons to perform searches for baryon number violation. The HIBEAM/NNbar experiment will search for neutron-antineutron and neutron-sterile neutron conversions with an improvement in sensitivity of several orders of magnitude compared to previous searches. HIBEAM is the first stage of the full-scale NNbar experiment planned to take place at a fundamental physics beamline at the ESS after 2026. This exploratory stage will facilitate the validation of detector technologies, the measurement of backgrounds in situ, and the development of background rejection methods. An overview of the HIBEAM/NNbar experiment along with the developments towards a prototype detector at Stockholm University are presented in this talk.

Speaker: Katherine Dunne (Stockholm University)

nnbar-spaatind-jan2020-kdunne (1).pdf

17:40 The Higgs Width in the SMEFT

We calculate the total and partial inclusive Higgs widths at leading order in the
Standard Model Effective Field Theory (SMEFT). We report results incorporating SMEFT
corrections for two and four body Higgs decays through vector currents in this limit. The
narrow width approximation is avoided and all phase space integrals are directly evaluated.
We explain why the narrow width approximation fails more significantly in the SMEFT
compared to the SM, despite the narrowness of the observed SU(2) × U(1) bosons in both
theories.

Speakers: Tyler Corbett, Tyler Corbett (NBI)

CorbettSpaatind20.pdf

18:00 The Oslo plasma lens at the CERN electron test accelerator

In particle accelerators, magnetic lenses are used to steer, focus, and control the beam. Typically, these are quadrupole magnets which means that the current must be off-center relative to the beam. Because of this, quadrupole magnets are used for focusing, which must defocus one plane (e.g. vertical) in order to focus the other plane (e.g. horizontal). This complicates optics design and performance.

By using plasma as the conductor, this challenge can be side-stepped. An active plasma focusing lens allows the beam to pass through the conductor, with the current parallel to the beam. This makes it possible to design compact and strong lenses focusing in both planes simultaneously.

This talk will present the design, operation, application, and challenges of using active plasma lenses for charged particle beams in the light of the plasma lens experiments at CLEAR, which are led by the High Energy Physics group at Oslo.

Speaker: Erik Adli (University of Oslo)

SPAATIND_2020___PLASMA_LENS.pptx

18:20 Status of the ATLAS ITk Strip Detector for the HL-LHC

The ATLAS Experiment is currently working on a series of upgrades in preparation for the High-Luminosity LHC, which is scheduled to start in 2026. One such upgrade will be to the inner-tracking system. The current Inner Detector will be completely replaced with a brand new, all-silicon Inner Tracker, consisting of a pixel detector near to the beam line and a large-area strip tracking detector. This talk will present the status of the strip tracking system as the project begins to move away from the R&D phase and towards the production phase. The role of the Scandinavian institutes within the project and the plans for the forth-coming production phase will be discussed.

Speaker: Craig Wiglesworth (Niels Bohr Institute)

04-01-20.pdf

18:40 Neutrino CP Violation with the European Spallation Source neutrino Super Beam project

After measuring in 2012 a relatively large value of the neutrino mixing angle θ13, the door is now open to observe for the first time a possible CP violation in the leptonic sector. The measured value of θ13 also privileges the 2nd oscillation maximum for the discovery of CP violation instead of the usually used 1st oscillation maximum. The sensitivity at this 2nd oscillation maximum is about three times higher than for the 1st oscillation maximum inducing a lower influence of systematic errors. Going to the 2nd oscillation maximum necessitates a very intense neutrino beam with the appropriate energy. The world’s most intense pulsed spallation neutron source, the European Spallation Source, will have a proton linac with 5 MW power and 2 GeV energy. This linac, under construction, also has the potential to become the proton driver of the world’s most intense neutrino beam with very high potential to discover a neutrino CP violation. The physics performance of that neutrino Super Beam in conjunction with a megaton underground Water Cherenkov neutrino detector installed at a distance of about 500 km from ESS has been evaluated. In addition, the choice of such detector will extent the physics program to proton–decay, atmospheric neutrinos and astrophysics searches. The ESS proton linac upgrades, the accumulator ring needed for proton pulse compression, the target station optimization and the physics potential are described. In addition to neutrinos, this facility will also produce at the same time a copious number of muons which could be used by a muon collider. The ESS neutron facility will be fully ready by 2023 at which moment the upgrades for the neutrino facility could start. This project is supported by the COST Action CA15139 "Combining forces for a novel European facility for neutrino-antineutrino symmetry-violation discovery" and the European Union’s Horizon 2020 research and innovation program under grant agreement No 777419.

Speaker: Eirik Gramstad (Researcher)

spaatind20_gramstad.pdf

20:30 → 21:30 submitted talks

20:30 Early equilibration, phase diagram and freeze-out in relativistic heavy ion collisions

Speaker: Evgeny Zabrodin (Department of Physics, University of Oslo)

zabrodin_spaatind_2020.pdf

20:50 Search for the electroweak production of charginos and sleptons decaying into final states with two electrons or muons in proton-proton collisions at s = 13 TeV with the ATLAS detector

The Standard Model (SM) of particle physics is currently the best theory for describing elementary particles and their interactions, but there are several problems and open questions related to it. For instance it does not incorporate gravity, and it does not explain dark matter, hence there is a need for new fundamental theories of nature beyond the current theory. A theory that addresses some of the problems with the SM is Supersymmetry, as a symmetry between fermions and bosons, which predicts a superpartner for each SM particle.
Here we present a search for the electroweak production of charginos and sleptons decaying into final states with two electrons or muons. The results are based on the full data set of proton-proton collisions recorded by the ATLAS detector during Run II of the Large Hadron Collider at s=13 TeV. Three R-parity-conserving scenarios where the lightest neutralino is the lightest supersymmetric particle are considered: the production of chargino pairs with decays via either W bosons or sleptons, and the direct production of slepton pairs.

Speaker: Helén Persson (University of Oslo)

Spaatind2020_Persson.pdf

21:10 A multi-TeV gamma-gamma collider based on plasma

The plasma wakefield accelerator has demonstrated high-gradient, high-efficiency acceleration of an electron beam. Numerical simulation results backed by theory indicate that also emittance preservation at the level needed for a high luminosity collider may be achievable in the blow out regime. Electron linacs based on plasma wakefield acceleration is therefore a promising technology for a compact future linear collider. However, there are currently no evident solutions for achieving the same performance for positron acceleration. Instead, two Multi-TeV electron linacs may be used to produce Multi-Tev gamma-gamma collisions. We discuss the option of a Multi-TeV gamma-gamma collider, including a brief look at the physics potential.

Speaker: Erik Adli (University of Oslo)

SPAATIND2020_GGCOLLIER_ADLI.pptx

Sunday, 5 January

08:30 → 10:00 invited talks

08:30 european strategy : overview on collider physics program

Speaker: Mogens Dam (Niels Bohr Institute)

ESPPU-Spaatind.pdf

09:15 Dark matter searches (I)

Speaker: Torsten Bringmann

Spaatind_Bringmann_1.pdf

15:00 → 16:30 invited talks

15:00 the Future Circular Collider

Speaker: Michelangelo Mangano (CERN)

Mangano_Norway_1.pdf

15:45 the Future Circular Collider

Speaker: Michelangelo Mangano (CERN)

17:00 → 19:00 submitted talks

17:00 Search for electroweakinos with small Δm using XGBoost

At the LHC, the production cross-section for supersymmetric partners of the colored Standard Model particles, namely squarks and gluinos, are expected to be much higher than for the sparticles that do not feel the strong interaction. So far there has been no indication of squarks or gluinos being produced. However, if the colored sparticles are too heavy to be produced at the LHC, we could still probe supersymmetric particles that interact weakly, if they were to be light enough. Charginos and neutralinos, collectively called electroweakinos, are fermionic superpartners of the electroweak gauge and higgs bosons. We here consider a search for a mass-degenerate pair of a lightest chargino and a next-to-lightest neutralino, which both decay to the lightest neutralino via the W and Z boson, respectively, into final states with two leptons, hadronic jets and missing transverse energy. A feasibility study will be shown for the application of Boosted Decision Trees (XGBoost) to increase the sensitivity to particularly challenging signal scenarios, where the mass-difference between the pair-produced electroweakinos and the lightest supersymmetric particle (LSP) is close to the mass of the W and Z bosons. The sensitivity will be compared to that of a more conventional cut-and-count analysis.

Speaker: Knut Oddvar Høie Vadla (University of Oslo)

SUSY-EW-ML-Spåtind20.pdf

17:20 Monte Carlo reweighting: Signal interpolation for ATLAS Dark Matter searches

Current Dark Matter (DM) searches at the ATLAS experiment require detailed signal hypotheses for various DM models. In order for a DM analysis to cover a large DM model parameter space, many Monte Carlo (MC) samples might be needed to accurately represent possible signatures/kinematics of the DM model. For complex experiments, such as ATLAS, detector level MC samples are computationally expensive and cannot be done for an arbitrary number of signal parameter points. Signal interpolation methods allow one to work around this by employing knowledge about the model to interpolate from existing detector level signal samples to new parameter points. The ATLAS search for DM in mono-Higgs decays, where the Higgs boson decays to two photons, employs a method of signal interpolation called MC reweighting, which is based on truth information from generator level MC samples.

Speaker: Kristian L. Bjørke (University of Oslo (NO))

kbjorke-Spaatind20-200105.pdf

17:40 Strangeness production in small systems - from revolution to resolution

ALICE measurements show that strangeness production increases with
multiplicity in small systems (pp and p-Pb collisions) at LHC energies. This
means that one has to give up the idea that a proton-proton collision can be
seen as an incoherent sum of parton-parton collisions; an idea that has been
central in most proton-proton generators, for example PYTHIA. To accommodate
the ALICE results, models have to introduce significant final state effects
and the question is now which ones are correct.

In this talk, I will first cover the general results and give examples of
models/mechanisms with final state interactions. I will then show recent more
differential results using event shapes, underlying event estimators and
correlations and discuss how these measurements can resolve the question of
the underlying physics mechanism.

Speaker: Peter Christiansen (Lund University)

spaatind_christiansen_animated.pdf

18:00 From Little Bang to Mini Bang: studying the primordial fluid at the LHC

The primary goal of the ultra-relativistic heavy-ion collision program at the Large Hadron Collider (LHC) is to study the properties of the Quark-Gluon Plasma (QGP), a novel state of strongly interacting matter which exists in the early universe, a few microseconds after Big Bang. Studies of azimuthal correlations of produced particles in ultra-relativistic heavy-ion collision have contributed significantly to the characterization of QGP. Anisotropic flow, which quantifies the anisotropy of the momentum distribution of final state particles, is sensitive to the fluctuating initial conditions and the transport properties of the created medium. The successful description of the measured anisotropic flow coefficients by hydrodynamic calculations suggests that the created medium behaves as a nearly perfect fluid.

In this talk, I will present flow measurements in lead--lead collisions at $\sqrt{s_{_{\rm NN}}} =$ 2.76 and 5.02 TeV and in Xenon--Xenon collisions at $\sqrt{s_{_{\rm NN}}} =$ 5.44 TeV at the LHC. The standard anisotropic flow, as well as the newly developed flow observables will be discussed. In addition, I will show the recent investigations of anisotropic flow in proton--lead at $\sqrt{s_{_{\rm NN}}} =$ 5.02 TeV and proton--proton collisions at $\sqrt{s} =$ 13 TeV, to search for a smallest drop of primordial fluid in the universe.

Speaker: Dr You Zhou (Niels Bohr Institute)

YZhou_Spaatind.pdf

18:20 To catch a long-lived particle

Conventional searches for new phenomena at collider experiments tend to focus on prompt particles, produced at the interaction point and decaying rapidly. New physics models including long-lived particles that travel a substantial distance in the detectors before decaying provide an interesting alternative, especially in light of the lack of new phenomena at the current LHC experiments, and could solve unanswered questions of the Standard Model. Long-lived particles have characteristic experimental signatures that, while making them clearly distinct from other processes, also could make them potentially invisible to current data-acquisition methods. Specific trigger strategies need to be in place to target long-lived particles. In this talk I will discuss this and propose strategies to not miss this kind of signature in future colliders.

Speaker: Rebeca Gonzalez Suarez (Uppsala University (SE))

Spaatind2020.pdf

18:40 Hardware-based track reconstruction for the ATLAS Trigger and Data Acquisition Phase-II system

The Large Hadron Collider (LHC) at CERN announced the High-Luminosity LHC (HL-LHC) project in 2013 with the aim of increasing the machine performance for new physics discoveries. Researchers will take full advantage of HL-LHC to study known mechanisms in greater detail and observe rare new physics phenomena. HL-LHC poses some challenges on all the LHC experiments: a ten times higher readout rate at each collision. To fully exploit the physics potential, the ATLAS experiment will upgrade its Trigger and Data Acquisition (TDAQ) system.
A hardware processor dedicated to particle tracking, Hardware-based Track Trigger (HTT), will be installed in the ATLAS TDAQ system between 2024 and 2026. The goal of HTT is a fast reconstruction of charged particle tracks using a massively parallel architecture. The HTT algorithms are designed to exploit the computing power of modern Field Programmable Gate Arrays (FPGAs), popular for their flexibility in functionality and high-speed communication, and custom Associative Memory (AM) ASICs, performing pattern recognition. The board called Pattern Recognition Mezzanine (PRM) is the key component of the HTT system, where both a state-of-the-art FPGA and AM ASICs are mounted.

Speaker: Alessandra Camplani (Niels Bohr Institute, University of Copenhagen)

Nordic_Camplani.pdf

20:30 → 21:30 submitted talks

20:30 Quasistable charginos in ultrapheral proton-proton collisions at the LHC

Speaker: Mikhail Vysotsky (ITEP, Moscow)

nordic2.pdf

20:50 Search for high-mass dilepton resonances using 139 fb−1 of pp collision data collected at √s = 13TeV with the ATLAS detector

A search for high-mass dielectron and dimuon resonances in the mass range of 250 GeV to 6 TeV is presented. The data were recorded by the ATLAS experiment in proton–proton collisions at a centre-of-mass energy of √s=13 TeV during Run 2 of the Large Hadron Collider and correspond to an integrated luminosity of 139 fb-1. A functional form is fitted to the dilepton invariant-mass distribution to model the contribution from background processes,and a generic signal shape is used to determine the significance of observed deviations from this background estimate. No significant deviation is observed and upper limits are placed at the 95% confidence level on the fiducial cross-section times branching ratio for various resonance width hypotheses.

In addition to presenting these results I will also give a short overview of my current projects and plans for my thesis.

Speaker: Mr Simen Hellesund

Spaatind2020SimenHellesund.pdf

21:10 Antinuclei as a Signature for Dark Matter

Antideuteron and antihelium nuclei have been proposed as a detection channel for dark matter annihilations and decays in the Milky Way, due to a low expected astrophysical background. To estimate both the signal for various dark matter models and the astrophysical background, one employs usually the coalescence model in a Monte Carlo framework. However, this approach lacks an underlying microscopic picture, and the numerical value of the coalescence parameter obtained from fits to different reactions varies considerably. We therefore develop a new coalescence model for deuteron, helium-3, tritium and their antinuclei based on the Wigner function representations of the produced nuclei states. This approach includes both the size of the formation region, which is process dependent, and momentum correlations in a semi-classical picture. The model includes a single universal free parameter that we tune to experimental data on antideuteron production in electron-positron, proton-proton and proton-nucleus collisions. The obtained value $a_0\sim 1\;\mathrm{fm}$ agrees well with its physical interpretation as the size of the formation region. We use this model to estimate the expected antinuclei signal on Earth from dark matter annihilations and the secondary production in the Galaxy, and comment on the expected signals in AMS-02 and the upcoming GAPS experiments.

Speaker: Jonas Tjemsland (NTNU)

tjemsland_presentation.pdf

Monday, 6 January

08:30 → 10:00 invited talks

08:30 Dark matter searches (II)

Speaker: Torsten Bringmann

Spaatind_Bringmann_2.pdf

09:15 The Compact Linear Collider

Speaker: Rickard Ström (DESY)

CLIC-DL-CR-detail_light.mp4

CLIC-flow-of-particles_light.mp4

clic_spaatind2020_stroem.pdf

15:00 → 16:30 invited talks

15:00 the Future Circular Collider

Speaker: Michelangelo Mangano (CERN)

Mangano_Norway_2.pdf

15:45 the Future Circular Collider

Speaker: Michelangelo Mangano (CERN)

17:00 → 19:00 submitted talks

17:00 Precision neutron beta decay experiments as a probe of BSM physics

Study of the neutron and nuclear beta decay correlation coefficients play important role in understanding the weak interaction. The correlation coefficients are sensitive to the exotic scalar and tensor interactions that are not included in the Standard Model. The information from low energy precision experiments is often complementary to that obtained from high-energy scale experiments. A short overview of neutron beta decay correlation experiments will be presented with emphasis on the BRAND project which is dedicated to measure simultaneously 11 neutron correlation coefficients (a, A, B, D, H, L, N, R, S, U, V) where 7 of them depend on the transverse electron polarization – a quantity which vanishes in the standard model. The BRAND project is starting on the cold neutron beamline PF1B at the ILL. The ultimate phase of the project is expected to be accomplished at ESS. I will discuss challenges, recent progress and plan of measurements.

Speaker: Dr Dagmara Rozpedzik (Jagiellonian University)

SPAATIND2020_final.pdf

17:20 Radiation hard pixel ‘3D’ sensors for use in ATLAS-ITk at LHC

Radiation hard pixel ‘3D’ sensors for use in ATLAS-ITk at LHC

Speakers: Bjarne Stugu (Bergen U), Bjarne Stugu (Bergen U)

Spaatind2020.pdf

17:40 Reconstructing the energy of electrons and photons using convolutional neural networks

This talk presents a study of the ability of a Convolutional Neural Networks (CNNs) to reconstruct the energy of electrons and photons. The measured energy of electromagnetic calorimeter cells are considered as pixels in an image, which the CNNs use as input along with a few scalar variables providing complementary information from other detectors. The CNNs are trained on simulated data, and subsequently evaluated on simulated samples not included in the training.

The best models improve the energy resolution on electrons (unconverted/converted photons) over the current performance by approximately 21% (29/20%)
fairly uniformly across energy and $\eta$. The performance of the CNNs are also more robust to increased pile-up, showing a slower deterioration of resolution with increasing $\langle \mu \rangle$.

Speaker: Mr Frederik Faye

presentation_cnn_ER_ffaye.pdf

18:00 Gaussian processes versus parametric background modeling

The signal to background ratio for Higgs decaying to 2 photons is small, therefore, a powerful estimation of the background is needed to accurately measure the signal. Since the underlying physical function is unknown, various functional parameterizations are considered for background estimation. When the number of events increases, the relative uncertainty decreases. This might give rise to some previously hidden features of the distribution, leading to the need for re-estimation of the background to avoid creating a spurious signal.
The current process is lengthy and awkward, and therefore, this study has focused on investigating Gaussian Processes (GP) as a new method for estimating the background and signal distributions. GP is a machine learning method that does not depend on a specific parametric function and could, therefore, be employed in numerous scientific areas. Although GP proved to be a challenging method to work with, the results obtained indicate that GP is a promising candidate for background estimation of the Higgs to 2 photons channel.

Speaker: Mr Simon Millerjord (University of Oslo)

SimonMillerjordSpaatind.pdf

18:20 Module production for ATLAS Inner Tracker (ITk) upgrade

In connection with the High Luminosity upgrade of the Large Hardron Collider, the current ATLAS Inner Detector will be replaced by a new all silicon detector - the Inner Tracker ITk. The ITk will use Silicon pixel and microstrip sensor technology across two primary geometries, a central barrel-like structure and two sets of wheels acting as end-caps for the detector. The Scandinavian ITk Cluster, consisting of physicists and engineers from Copenhagen, Lund, Oslo and Uppsala University, will be responsible for producing 10 % of the microstrip modules for the End-cap.

This presentation will give a brief overview of the ITk detector design, and then go into the development of a robot for high precision glue dispensing, to be used in mounting the read-out, powering and control electronics on to the surface of Silicon microstrip sensors.

Speaker: Jonas Steentoft (Student at NBI)

Sp_tind_2020___Glue_robot_development_for_ITk_module_assembly.pdf

18:40 Accelerating new physics searches with XSEC

Hand in hand with the large-scale experimental attempts to observe traces of supersymmetry at the LHC, there are ongoing efforts to assess the combined power of all searches so far. Such global fits to experimental results require accurate theoretical predictions of the production cross sections for supersymmetric particles. However, computing higher-order contributions is prohibitively time-consuming and a major bottleneck for such scans in high-dimensional parameter spaces, that take into account a plethora of constraints. This presentation will showcase XSEC, a new software tool that employs the power of Gaussian Processes to radically speed up cross-section evaluations and to make detailed uncertainty estimates.

Speaker: Jeriek Van den Abeele (University of Oslo)

Online slides

xsec-spaatind.pdf

19:30 → 22:30 Conference Dinner at Thon Hotel

Tuesday, 7 January

08:00 → 08:30 Departure for the Airport