BOOST 2017
Embassy Suites Buffalo
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Poster Session
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Public Event: Welcome Reception
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Introductory Talks
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2
Experimental OverviewSpeaker: Lily Asquith (University of Sussex (UK))
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10:30
Coffee
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Searches
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4
Searches for new physics using jet grooming and substructure (ATLAS)
Models predicting the production and decay of supersymmetric (SUSY) particles often have promising search channels involving decays through heavy intermediate states such as top quarks and heavy bosons. However, unlike in most exotics scenarios these heavy states are only moderately boosted which can make traditional substructure techniques less useful and motivates the development of alternative techniques. The results of several SUSY analyses using substructure techniques are presented.
Speaker: Jonathan Burr (University of Oxford (GB)) -
5
Search for diboson resonances at CMS
Beyond the standard model theories like Extra-Dimensions and Composite Higgs scenarios predict the existence of very heavy resonances compatible with a spin 0 (Radion),spin 1 (W’, Z’) and spin 2 (Graviton) particle with large branching fractions in pairs of standard model bosons and negligible branching fractions to light fermions. We present an overview of searches for new physics containing photons, W, Z or H bosons in the final state, using proton-proton collision data collected with the CMS detector at the CERN LHC. Many analyses use techniques to identify and reconstruct highly boosted final states that are created in these topologies.
Speakers: Jennifer Ngadiuba (CERN), Jennifer Ngadiuba (Univ. Zürich)
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12:30
Lunch
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Searches
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6
Searches for exotic resonances and dark matter with boson tagging (ATLAS)
Several theories beyond the standard model predict new particles decaying resonantly into dibosons or coupling to dark matter particles. Jet substructure and boson tagging techniques play a crucial role in searches for dark matter and diboson resonances in boosted topologies. In this talk, the application of these techniques at ATLAS will be discussed in the context of recent searches for dark matter and diboson resonances. Latest results for these searches in pp collisions at 13 TeV using an integrated luminosity of 36/fb will be presented.
Speaker: Daniel Isaac Narrias Villar (Ruprecht-Karls-Universitaet Heidelberg (DE)) -
7
Search for new resonances coupling to third generation quarks at CMS, and Dark Matter
We present a search for new massive particles (such as Z prime and W prime resonances) decaying to heavy-flavour quarks with the CMS detector at the LHC, and dark matter signatures involving boosted jets. Resonant ttbar, tb, and heavy quark plus vector-like quark production, along with missing pt plus boosted objects, are investigated. We use proton-proton collision data recorded at a centre-of-mass energy of 13 TeV. The search is performed in both hadronic and semileptonic decay channels of the top quark or of the top-partners. Due to the high momentum range in which these objects are produced, specific reconstruction algorithm and selections are employed to address the identification of these boosted signatures.The results are presented in terms of upper limits on the model cross section.
Speakers: Thomas Peiffer (Hamburg University (DE)), Thomas Peiffer (University of Hamburg) -
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Searches for exotic resonances with top tagging (ATLAS)
Several models of physics beyond the Standard Model contain preferential couplings to top quarks. We present an overview of searches for new physics containing boosted top quarks in the final state, using proton-proton collision data collected with the ATLAS detector at the LHC at a centre-of-mass energy of 13 TeV. These results cover heavy gauge bosons, excited third generation quarks, or decay channels to vector-like top partner quarks.
Speaker: Junpei Maeda (Kobe University (JP)) -
9
Search for vector-like quarks, excited quarks and squarks in boosted final states at CMS
We present results of searches for massive top and bottom quark partners using proton-proton collision data collected with the CMS detector at the CERN LHC at a center-of-mass energy of 8 and 13 TeV. These considered models include vector-like quarks, excited quarks and supersymmetric quark partners. These particles can be produced singly or in pair and their decays result in a variety of final states, containing top and bottom quarks, gauge and Higgs bosons. We search using several categories of reconstructed objects, from multi-leptonic to fully hadronic final states. In the latter, substructure techniques are used to identify hadronically decaying top quarks and bosons, to resolve these boosted final states and to increase the sensitivity of the searches. We set exclusion limits on the mass and cross sections of the hypothetical BSM particles
Speaker: Daniel Gonzalez Vazquez (Hamburg University (DE))
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6
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16:00
Coffee Break
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Algorithms
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10
Jet Fragmentation and Fractal Observables
I will discuss fractal jet observables, which are collinear-unsafe but can be described by generalizing the formalism of fragmentation functions. Generalized fragmentation functions (GFFs) are nonperturbative objects with a calculable RG running. In contrast to the linear DGLAP equations for ordinary fragmentation functions, GFFs evolve nonlinearly, since they encode correlations among subsets of hadrons in a jet. I review some special cases of generalized fragmentation functions already in the literature, including jet charge and track functions. I then present new fractal observables based on hierarchical clustering trees, which exhibit promising performance for discriminating quark jets from gluon jets.
Speaker: Benjamin Elder (Massachusetts Institute of Technology) -
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Recursive Soft Drop
In this talk, we introduce a new jet substructure method based on a
recursive iteration of the Soft Drop algorithm through both branches
of the clustering tree.
Recursive soft drop uses an additional parameter N to define the
number of layers of soft drop declustering, providing an optimized
grooming strategy for boosted objects with (N+1)-prong decays, as well
as improved stability in high pileup conditions. We discuss the
infinite N limit, where groomed jets have a null area, and investigate
the robustness of recursive soft drop to non-perturbative effects.
We show promising applications to jet mass resolution in boosted top
and W bosons, and demonstrate how recursive soft drop grooming can
improve pileup mitigation when used in conjunction with existing
pileup-removal methods.Speaker: Frederic Alexandre Dreyer (MIT)
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10
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Measurements and Modeling: Open Data and Heavy Ions
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12
Jet Substructure Analysis with CMS Open Data
In this talk, I present the first analysis of the substructure of jets using the 2010 CMS Open Data. Our analysis is based on 36/pb of 7 TeV proton-proton collisions, where in each event the leading jet has a transverse momentum larger than 150 GeV. We measure classic jet substructure observables like jet mass and multiplicity and compare the results to parton shower generators. We find excellent agreement even before accounting for the impact of detector effects. We then perform a substructure analysis using soft drop declustering to study the two-prong substructure of jets and test the 1->2 splitting function of QCD. I discuss how our analysis strategy can be used as a starting point for other particle physicists to explore novel analysis opportunities that are now possible with this open data release.
Speaker: Aashish Tripathee (Massachusetts Institute of Technology) -
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Confronting jet quenching with jet grooming: splitting function and jet mass distribution in heavy ion collisions
We present the first calculations of the momentum sharing and angular separation distributions between the leading subjets inside a reconstructed jet, as well as the jet mass distribution modification in heavy ion collisions. These observables are sensitive to the early and late stages of the in-medium parton shower evolution and allow us to probe the quark-gluon plasma across a wide range of energy scales. We use the medium-induced splitting functions obtained in the framework of soft-collinear effective theory with Glauber gluon interactions to calculate the subjet distributions. Qualitative and in most cases quantitative agreement between theory and preliminary CMS measurements suggests that the parton shower in heavy ion collisions can be dramatically modified early in the branching history. Predictions for the subjet angular distribution is also presented which will illuminate the nature of the medium-induced radiations. On the other hand, using renormalization group techniques we resum the jet mass at next-to-leading logarithmic accuracy for groomed jets with small radii, and we include the medium contributions consistently. We find that the jet mass modification is sensitive to the medium scale and allows for a precise extraction of the medium properties.
Speaker: Dr Yang-Ting Chien (Massachusetts Institute of Technology) -
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Jet substructure modifications in heavy-ion collisions
Significant experimental and theoretical activity at the LHC is dedicated to the study of hot and dense QCD matter created in head-on heavy-ion collisions. Measurements of fully reconstructed jets in these collisions allow to examine new aspects of this exotic state via its coupling to perturbative degrees of freedom. The potential sensitivity of jet substructure observables to modifications in the plasma has recently sparked an intense theoretical activity leading to an improved understanding of jet fragmentation and the dynamics of the underlying medium. In this talk, I will review the recent advances and highlight the role of quantum and colour decoherence processes that govern how jets are resolved and, subsequently, lose energy through medium-induced bremsstrahlung. These processes have a profound effect on the jet sample and lead to substructure modifications. I will also discuss how these modifications can be observed in experiments, focussing on aspects of the hardest splitting in the jet cone, as well as provide an overview of possible contamination of non-perturbative processes.
Speaker: Konrad Tywoniuk (CERN)
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12
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Directed Dinner: Directed Dinner 1
Experts on particular topics will be hosting "directed dinners" where people can discuss and/or ask questions about the topic.
Options for directed dinner topics:
- Deep thinking versus deep learning... philosophy?
- Extrapolation of jet mass scales to high pt (from diboson searches from CMS)
- Background uncertainties at high pt (from diboson searches from ATLAS)
- New boosted signatures (multileptons + boosted objects? dijets with two massive subjets? others?)
- Mass shape for Z+jets MC at 500 GeV (from diboson searches)
- To open data or to not open data?
- Heavy Ions calculations and measurements
Places to try:
- Anchor Bar (wings, $$): https://www.google.com/maps/place/Anchor+Bar/@42.9023801,-78.8684747,15z/data=!4m2!3m1!1s0x0:0x42feff60b17ba88c?sa=X&ved=0ahUKEwjZht3QhJHVAhUEiVQKHXkNBcsQ_BIIfjAN
- Seabar (sushi, $$$):
https://www.google.com/maps/place/Seabar+Sushi/@42.891173,-78.87216,17z/data=!3m1!4b1!4m5!3m4!1s0x89d08fdbedd8732b:0x71af3a34897fcb56!8m2!3d42.891173!4d-78.869966- Toutant (southern food, $$$):
https://www.google.com/maps/place/Toutant/@42.8902875,-78.8724973,17z/data=!4m12!1m6!3m5!1s0x89d31245a7c8b73d:0x3f85cf9959a48ea4!2sToutant!8m2!3d42.8902875!4d-78.8703033!3m4!1s0x89d31245a7c8b73d:0x3f85cf9959a48ea4!8m2!3d42.8902875!4d-78.8703033
- Pizza Plant (well... pizza! $$)
https://www.google.com/maps/place/Pizza+Plant+Italian+Pub+-+Canalside/@42.884753,-78.8801689,14.91z/data=!4m8!1m2!2m1!1sPizza+plant!3m4!1s0x0:0xc98b34db5e687f5e!8m2!3d42.8783935!4d-78.8763106- Pearl Street Grille (pub food, $$):
https://www.google.com/maps/place/Pearl+Street+Grill+%26+Brewery/@42.8810499,-78.8795978,17z/data=!4m12!1m6!3m5!1s0x89d31259e9c4b085:0x7ce880149997095c!2sPearl+Street+Grill+%26+Brewery!8m2!3d42.8810499!4d-78.8774038!3m4!1s0x89d31259e9c4b085:0x7ce880149997095c!8m2!3d42.8810499!4d-78.8774038- Buffalo Riverworks (errr... hard to describe, but awesome and $$):
https://www.google.com/maps/place/Buffalo+RiverWorks/@42.8700909,-78.8741426,17z/data=!4m12!1m6!3m5!1s0x89d3122f5c17a293:0x6778b2cec05b3acb!2sBuffalo+RiverWorks!8m2!3d42.8700909!4d-78.8719486!3m4!1s0x89d3122f5c17a293:0x6778b2cec05b3acb!8m2!3d42.8700909!4d-78.8719486- Dinosaur barbecue (bbq + brisket, $$):
https://www.google.com/maps?ll=42.892591,-78.874144&z=14&t=m&hl=en-US&gl=US&mapclient=embed&q=301+Franklin+St+Buffalo,+NY+14202
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Measurements and Modeling
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Electro-weak splitting functions and electro-weak shower
We derive the electroweak (EW) collinear splitting functions up to single logs. Especially we systematically incorporate EW symmetry breaking (EWSB), by imposing a particularly convenient gauge choice (dubbed “Goldstone Equivalence Gauge”) that disentangles the effects of Goldstone bosons and gauge fields in the presence of EWSB. As a result, we are able to derive splitting functions up to leading power corrections in v/kT. We also implement a comprehensive, practical EW showering scheme based on these splitting functions using a Sudakov evolution formalism. The implementation of EW showering includes novel features such as ``ultra-collinear" splitting , matching between shower and decay, and mixed-state evolution of neutral bosons (γ/Z/h) using density-matrices, kinematic back-reaction corrections in multi-stage showers. We demonstrate those new phenomena and features at O(1–10 TeV) energies with some examples.
Speaker: Junmou Chen (University of Pittsburgh) -
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Precision Top Mass Determination at the LHC with Jet Grooming
We show how the top mass can be extracted kinematically using cross sections for event shapes observables calculated using effective field theory methods. With the help of Soft Drop grooming done at a level that does not disturb the radiation that can modify the top mass definition, while still isolating the top jet, we obtain a distribution that is only mildly sensitive to the underlying event and initial state radiation. The data from LHC for top jets can thus be made to look very similar to e+e- collisions, and we compare Pythia results with those from our effective theory predictions.
Speaker: Mr Aditya Pathak (Massachusetts Institute of Technology)
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10:30
Coffee
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Measurements and Modeling
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19
Higher-order effects in parton showersSpeaker: Marek Schoenherr (Universitaet Zuerich (CH))
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21
Generative Adversarial Networks for Jet Simulation
We introduce the first use of deep neural network-based generative modeling for high energy physics (HEP). Our novel Generative Adversarial Network (GAN) architecture is able cope with the key challenges in HEP images, including sparsity and a large dynamic range. For example, our Location-Aware Generative Adversarial Network learns to produce realistic radiation patterns inside high energy jets simultaneously for boosted W boson and generic quark and gluon jets. The pixel intensities of the GAN-generated images faithfully span many orders of magnitude and reproduce the distributions of important low-dimensional physical properties (e.g. jet mass, n-subjettiness, etc.). We provide many visualizations of what the GAN has learned, to build additional confidence in the algorithm. Our results demonstrate that high-fidelity, fast simulation through GANs is a promising application of deep neural networks for solving one of the most important challenges facing HEP, and in particular jet-substructure, today.
Speakers: Michela Paganini (Yale University (US)), Luke Percival De Oliveira, Ben Nachman (Lawrence Berkeley National Lab. (US))
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19
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12:30
Lunch
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Measurements and Modeling
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22
A study of jet mass distributions with grooming
We perform a phenomenological study of the invariant mass distribution of hadronic jets produced in pp collisions, in conjunction with a groomer, in particular the modified MassDrop Tagger (equivalent to Soft Drop with angular exponent $\beta = 0$). Our calculation resums large logarithms of the jet mass and includes the full dependence on the groomer’s energy threshold $z_\text{cut}$ , and it is matched to fixed-order QCD matrix elements at next-to-leading order. We accounted for non-perturbative contributions by including a correction factor derived from Monte Carlo parton-shower simulations. Furthermore, we consider two different possibilities for the jet transverse momentum: before or after grooming. We show that the former should be preferred for comparisons with upcoming experimental data essentially because the mMDT transverse momentum spectrum is not collinear safe.
Speaker: Laís Sarem Schunk (IPhT, CEA - Saclay) -
23
ATLAS standard Model Measurements using Jet grooming and substructure
Boosted topologies allow to explore Standard Model processes in kinematical regimes never tested before. In such LHC challenging environments, standard reconstruction techniques quickly hit the wall. Targeting hadronic final states means to properly reconstruct energy and multiplicity of the jets in the event. In order to be able to identify the decay product of boosted objects, i.e. W bosons, tt pairs or Higgs produced in association with tt pairs, the ATLAS experiment is currently exploiting several algorithms using jet grooming and jet substructure. This contribution will cover the following ATLAS measurements: the production of W plus high transverse momentum jets, tt differential cross section production and the search for ttH production with boosted top quarks final states. Standard Model measurements offer the perfect field to test the performances of new jet tagging techniques which will become even more important in the search for new physics in highly boosted topologies.
Speaker: Giulia Ucchielli (Universita e INFN, Bologna (IT)) -
24
Jet substructure measurements at CMS, including heavy ions
A number of measurements are presented that utilize and/or investigate jet substructure.
The measurement of top production and the investigation of its properties in the boosted regime is gaining increasing attention with the rapid increase of the production cross sections at 13 TeV. The CMS experiment has measured the production cross section as function of the transverse momentum and rapidity of the (anti)top quark in final states containing one charged lepton at 8 TeV and no leptons at 13 TeV. These measurements extend the reach of the ones performed in the regime where the objects from the top quark decays are resolved and are compared to the latest fixed order prediction calculations as well as to state-of-the-art MCs. In addition to these the first measurement of the differential cross section as function of the top jet mass, and the extraction of the top quark mass in the boosted regime is presented.
Measurements of the differential cross section of dijets with respect to jet mass and pt, as well as the measurement of the jet charge, are also presented. These provide important tests of QCD in the jetty regime. The jet mass measurement is computed for ungroomed jets, and also for jets groomed with the soft drop algorithms, providing the capability to compare to theoretical predictions of the jet mass for the first time at a hadron collider.
Results using jet substructure are also included from heavy ion collisions, including the jet fragmentation and mass.
Speaker: Philip Coleman Harris (CERN)
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22
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15:30
Coffee
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Algorithms: Quarks and Gluons
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25
Casimir Meets Poisson: Improved Quark/Gluon Discrimination with Counting Observables
Charged track multiplicity is among the most powerful observables for discriminating quark- from gluon-initiated jets. Despite its utility, it is not infrared and collinear (IRC) safe, so perturbative calculations are limited to studying the energy evolution of multiplicity moments. While IRC-safe observables, like jet mass, are perturbatively calculable, their distributions often exhibit Casimir scaling, such that their quark/gluon discrimination power is limited by the ratio of quark to gluon color factors. In this paper, we introduce new IRC-safe counting observables whose discrimination performance exceeds that of jet mass and approaches that of track multiplicity. The key observation is that track multiplicity is approximately Poisson distributed, with more suppressed tails than the Sudakov peak structure from jet mass. By using an iterated version of the soft drop jet grooming algorithm, we can define a "soft drop multiplicity" which is Poisson distributed at leading-logarithmic accuracy. In addition, we calculate the next-to-leading-logarithmic corrections to this Poisson structure. If we allow the soft drop groomer to proceed to the end of the jet branching history, we can define a collinear-unsafe (but still infrared-safe) counting observable. Exploiting the universality of the collinear limit, we define generalized fragmentation functions to study the perturbative energy evolution of collinear-unsafe multiplicity.
Speaker: Christopher Frye (Harvard) -
26
Quark/Gluon Discrimination with Jet-Images and Deep Learning
I will discuss recent work addressing light-quark/gluon jet discrimination using image recognition techniques from deep learning. The usual jet-image framework is supplemented by adding “color" to the images in the form of local energy deposit and count information. Overall, this approach outperforms multivariate analyses of traditional jet observables and provides a theoretical upper bound of the discrimination performance of IRC-safe information. Though different Monte Carlo programs are known to produce different quark and gluon jets, the deep learning techniques are found to be surprisingly insensitive to these differences.
Speaker: Patrick Komiske (MIT) -
27
ATLAS quark/gluon tagging
Distinguishing quark-initiated from gluon-initiated jets is useful for many measurements and searches at the LHC. We present a quark-initiated versus gluon-initiated jet tagger from the ATLAS experiment using the number of reconstructed charged particles inside the jet. The measurement of the charged-particle multiplicity inside jets from Run 1 is used to derive uncertainties on the tagger performance for Run 2. With an efficiency of 60% to select quark-initiated jets, the efficiency to select gluon-initiated jets is between 10 and 20% across a wide range in jet $p_T$ up to 1.5 TeV with about an absolute 5% systematic uncertainty on the efficiencies. In addition, we also present preliminary studies on a tagger for the ATLAS experiment using the full radiation pattern inside a jet processed as images in deep neural network classifiers.
Speaker: Francesco Rubbo (SLAC National Accelerator Laboratory (US)) -
28
CMS quark/gluon tagging
Distinguishing between quark and gluon initiated jets relies on differences in the QCD shower patterns and is an important ingredient for a number of physics analyses. We present the current status of quark gluon tagging in CMS including comparisons using 13 TeV collision data.
Speakers: Yuta Takahashi (Univ. Zürich), Yuta Takahashi (Universitaet Zuerich (CH))
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25
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Directed Dinner
Experts on particular topics will be hosting "directed dinners" where people can discuss and/or ask questions about the topic.
Options for directed dinner topics:
- Deep thinking versus deep learning... philosophy?
- Extrapolation of jet mass scales to high pt (from diboson searches from CMS)
- Background uncertainties at high pt (from diboson searches from ATLAS)
- New boosted signatures (multileptons + boosted objects? dijets with two massive subjets? others?)
- Mass shape for Z+jets MC at 500 GeV (from diboson searches)
- To open data or to not open data?
- Heavy Ions calculations and measurements
Places to try:
- Anchor Bar (wings, $$): https://www.google.com/maps/place/Anchor+Bar/@42.9023801,-78.8684747,15z/data=!4m2!3m1!1s0x0:0x42feff60b17ba88c?sa=X&ved=0ahUKEwjZht3QhJHVAhUEiVQKHXkNBcsQ_BIIfjAN
- Seabar (sushi, $$$):
https://www.google.com/maps/place/Seabar+Sushi/@42.891173,-78.87216,17z/data=!3m1!4b1!4m5!3m4!1s0x89d08fdbedd8732b:0x71af3a34897fcb56!8m2!3d42.891173!4d-78.869966- Toutant (southern food, $$$):
https://www.google.com/maps/place/Toutant/@42.8902875,-78.8724973,17z/data=!4m12!1m6!3m5!1s0x89d31245a7c8b73d:0x3f85cf9959a48ea4!2sToutant!8m2!3d42.8902875!4d-78.8703033!3m4!1s0x89d31245a7c8b73d:0x3f85cf9959a48ea4!8m2!3d42.8902875!4d-78.8703033
- Pizza Plant (well... pizza! $$)
https://www.google.com/maps/place/Pizza+Plant+Italian+Pub+-+Canalside/@42.884753,-78.8801689,14.91z/data=!4m8!1m2!2m1!1sPizza+plant!3m4!1s0x0:0xc98b34db5e687f5e!8m2!3d42.8783935!4d-78.8763106- Pearl Street Grille (pub food, $$):
https://www.google.com/maps/place/Pearl+Street+Grill+%26+Brewery/@42.8810499,-78.8795978,17z/data=!4m12!1m6!3m5!1s0x89d31259e9c4b085:0x7ce880149997095c!2sPearl+Street+Grill+%26+Brewery!8m2!3d42.8810499!4d-78.8774038!3m4!1s0x89d31259e9c4b085:0x7ce880149997095c!8m2!3d42.8810499!4d-78.8774038- Buffalo Riverworks (errr... hard to describe, but awesome and $$):
https://www.google.com/maps/place/Buffalo+RiverWorks/@42.8700909,-78.8741426,17z/data=!4m12!1m6!3m5!1s0x89d3122f5c17a293:0x6778b2cec05b3acb!2sBuffalo+RiverWorks!8m2!3d42.8700909!4d-78.8719486!3m4!1s0x89d3122f5c17a293:0x6778b2cec05b3acb!8m2!3d42.8700909!4d-78.8719486- Dinosaur barbecue (bbq + brisket, $$):
https://www.google.com/maps?ll=42.892591,-78.874144&z=14&t=m&hl=en-US&gl=US&mapclient=embed&q=301+Franklin+St+Buffalo,+NY+14202
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Future Colliders: Phenomenology
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29
Radiative Decays of the Higgs Boson to a Pair of Fermions
We present a phenomenological study of the Higgs radiative decay to a fermion pair. We include the chirality-flipping diagrams via the Yukawa couplings at the order $\mathcal{O}(y_f^2 \alpha)$, the chirality-conserving contributions via the top-quark loops of the order $\mathcal{O}(y_t^2 \alpha^3)$, and the electroweak loops at the order $\mathcal{O}(\alpha^4)$. All the leptonic radiative decays are potentially observable at the LHC Run 2 or the HL-LHC. The lepton pairs that come from virtual photon conversions are highly boosted and tend to merge into clusters, which may require special treatments for identification. We also study the process $h \to c\bar c \gamma$ and evaluate the observability at the LHC. We find it potentially comparable to the other related studies and better than the $h \to J/\psi\ \gamma$ channel in constraining the charm-Yukawa coupling.
Speaker: Xing Wang (University of Pittsburgh) -
30
Higgs to light jets
We study the Higgs boson (h) decay to two light jets at the 14 TeV High-Luminosity-LHC (HL-LHC), where a light jet (j) represents any non-flavor tagged jet from the observational point of view. The decay mode h→gg is chosen as the benchmark since it is the dominant channel in the Standard Model (SM), but the bound obtained is also applicable to the light quarks (j=u,d,s). We estimate the achievable bounds on the decay branching fractions through the associated production Vh (V=W±,Z). Events of the Higgs boson decaying into heavy (tagged) or light (un-tagged) jets are correlatively analyzed. We find that with 3000 fb−1 data at the HL-LHC, we should expect approximately 1σ statistical significance on the SM Vh(gg) signal in this channel. This corresponds to a reachable upper bound BR(h→jj)≤4 BRSM(h→gg) at 95% confidence level. A consistency fit also leads to an upper bound BR(h→cc)<15 BRSM(h→cc) at 95% confidence level. The estimated bound may be further strengthened by adopting multiple variable analyses, or adding other production channels.
Speaker: Zhuoni Qian (University of Pittsburgh)
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29
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Algorithms
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31
Small R jet reconstruction and calibration algorithms (ATLAS)
Small radius jets with R = 0.4 are standard tools in ATLAS for physics analysis. They are calibrated using a sequence of Monte Carlo simulation-derived calibrations and corrections followed by in-situ calibrations based on the transverse momentum balance between the probed jets and well-measured reference signals. In this talk the inputs to jet reconstruction in LHC Run 2 comprising calorimeter cell clusters, reconstructed charge particle tracks, and particle flow objects, are discussed together with the jet energy calibration scheme. Selected results from the performance of the procedure and the associated systematic uncertainties are presented.
Speaker: Peter Loch (University of Arizona (US)) -
32
Jet energy scale and resolution measurements at CMS
Measurement of jet energy scale corrections and resolution, and performance of jet mass scale and resolution based on data collected at a center-of-mass energy of 13 TeV are presented in this report. Jet energy scale corrections at CMS accounts for the effects of pileup, and dependencies of response of jets on transverse momenta and detector non-uniformity. The differences in response measured in data and MC are extracted using QCD multijet, Z+jets, photon+jets and zero bias events. A measurement of differential jet production cross section as a function of groomed jet mass is also presented in this report.
Speakers: Anastasia Karavdina (Hamburg University (DE)), Anastasia Karavdina (University of Hamburg) -
33
Large R jet reconstruction and calibration algorithms (ATLAS)
Large-R jets are used by many ATLAS analyses working in boosted regimes. ATLAS Large-R jets are reconstructed from locally calibrated calorimeter topoclusters with the Anti-k_{t} algorithm with radius parameter R=1.0, and then groomed to remove pile-up with the trimming algorithm with f_{cut} 0.05 and subjet radius R=0.2. Monte Carlo based energy and mass calibrations correct the reconstructed jet energy and mass to truth, followed by in-situ calibrations using a number of different techniques. Large-R jets can also be reconstructed using small-R jets as constituents, instead of topoclusters, a technique called jet reclustering, or from track calo clusters (TCCs), which are constituents constructed using both tracking and calorimeter information. An overview of large-R jet reconstruction will be presented here, along with selected results from the jet mass calibrations, both Monte Carlo based an insitu, from jet reclustering, and from track calo clusters.
Speaker: Joe Taenzer (Tel Aviv University (IL))
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31
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10:30
Coffee
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Algorithms
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34
W/H tagging in CMS
The case of CMS "two prong" tagging algorithms are presented, specifically detailing the cases of W and H boson tagging. This talk will focus on the most recent algorithms used in LHC Run II analyses and their validation in data.
Speakers: Thea Aarrestad (Universitaet Zuerich (CH)), Thea Aarrestad (Univ. Zürich) -
35
W/Top/H tagging in ATLAS
We present updates of W, Top and Higgs tagging studies with the ATLAS detector. The performance of 2 variable taggers, HEPTopTagger and shower deconstruction are compared in Monte Carlo simulations. To asses the modelling of the taggers’ performance, the tagging efficiencies are measured, with the full 2015+2016 dataset, in semi-leptonic top quark pair events and the background rejections are measured in dijet and photon+jet topologies. Recent developments in subjet reconstruction techniques for high transverse momentum Higgs->bb tagging are also presented.
Speaker: Nurfikri Norjoharuddeen (University of Oxford (GB)) -
36
Top tagging at CMS
An overview of methods for identifying decays of boosted top quarks with the CMS detector in Run II is presented.
Speakers: Torben Dreyer (Hamburg University (DE)), Torben Dreyer (University of Hamburg)
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12:30
Lunch
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Algorithms: Machine Learning
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37
B-tagging without tracks in highly boosted TeV Jets using an Artificial Neural Network
The performance of standard tagging algorithms begins to fall in the case of highly boosted B hadrons (γβ=p/m>200). This work builds on our previous study that uses the jump in hit multiplicity among the pixel layers of an ATLAS or CMS-like detector when a B hadron decays within the detector volume. Consequently, tracking is not required.
First, multiple pp interactions within a finite luminous region were found to have little effect. Second, the study has been extended to use the multivariant techniques of an artificial neural network (ANN). After training, the ANN shows significant improvements to the ability to reject light-quark and charm jets; thus increasing the expected significance of the technique.
Speaker: Todd Brian Huffman (University of Oxford (GB)) -
38
Deep-learning Top Taggers and No End to QCD
Machine learning based on convolutional neural networks can be used to study jet images from the LHC. Top tagging in fat jets offers a well-defined framework to establish our DeepTop approach and compare its performance to QCD-based top taggers. We optimize a network architecture to identify top quarks in Monte Carlo simulations of the Standard Model production channel. Using standard fat jets we then compare its performance to a multivariate QCD-based top tagger. We show that both approaches lead to comparable performance, establishing convolutional networks as a promising new approach for multivariate hypothesis-based top tagging. Finally, we will comment on new results using machine-learning-based subjet methods.
Speaker: Gregor Kasieczka (Eidgenoessische Technische Hochschule Zuerich (CH)) -
39
Identification of boosted top quarks and W bosons with Machine learning in ATLAS
We present techniques for the identification of hadronically-decaying W bosons and top quarks using high-level features as inputs to boosted decision trees and deep neural networks in the ATLAS experiment at sqrt(s)=13 TeV. The performance of these machine learning based taggers is compared in Monte Carlo simulation with various different tagging algorithms. An improvement in background rejection with respect to different taggers is observed. In addition, the performance of the machine learning taggers is examined in full Run-II data set in top quark pair, dijet and photon+jet topologies.
Speaker: Oliver Majersky (Comenius University (SK)) -
40
Machine Learning at CMS
Machine learning has become an important tool in particle physics, and in jet substructure and boosted objects in particular. This presentation shows the breadth of applications from CMS, from "DeepFlavor" b-tagging to new techniques of substructure applications.
Speakers: Jan Kieseler (CERN), Jan Kieseler (CERN) -
41
Pileup Mitigation with Machine Learning
We develop a new pileup mitigation technique based on multi-channel jet images using convolutional neural nets. The input to the network is a three-channel jet image: the calorimeter "pixel" information of charged leading vertex particles, charged pileup particles, and neutral particles . We compare our algorithm to existing methods on a wide range of simple and complex jet observables up to 140 collisions per bunch crossing. In addition, we investigate what aspects of the event our algorithms are utilizing and also test the method robustness.
Speaker: Eric Metodiev (Massachusetts Institute of Technology)
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37
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Committee MeetingConvener: Peter Loch (University of Arizona (US))
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BOOST 2020 Proposals
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45
Int.Comm. Discussion
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Public Event
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46
Universal: A guide to the cosmosSpeaker: Jeffrey Forshaw (University of Manchester)
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46
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Algorithms: Pileup
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Soft Puppi
Pileup is one of the biggest challenges facing the LHC and HL-LHC physics programs. Many reconstruction methods have been proposed for mitigating its effects across a broad range of physics metrics such as jet and jet substructure response and resolution, missing transverse energy performance, and lepton identification. Among the most successful are the SoftKiller and Pileup Per Particle Identification (PUPPI) algorithms which operate on the event constituents and have been demonstrated to holistically improve these physics metrics. In this talk, we explore the complementarity of these algorithms in order to optimize an algorithm for both simplicity and performance.
Speaker: Jennifer Kathryn Roloff (Harvard University (US)) -
48
Pileup mitigation (ATLAS)
Simultaneous proton-proton collisions, or pileup, at the LHC has a significant impact on jet reconstruction, requiring the use of advanced pileup mitigation techniques. Pileup mitigation may occur at several stages of the reconstruction process, and ATLAS uses a combination of schemes, including constituent reconstruction methods, constituent-level pileup-mitigation techniques, and jet-level pileup-mitigation algorithms. This talk describes the two constituent-reconstruction methods for jets used on ATLAS: TopoClustering and Particle Flow. This talk also has a first look at the performance of several constituent-level pileup mitigation techniques on ATLAS, including Constituent Subtraction, Voronoi Subtraction, SoftKiller, and the Cluster Vertex Fraction. Finally, other developments in tagging pileup jets is discussed, such as the forward jet vertex tagger (fJVT), which uses jet shapes and topological information to tag jets.
Speaker: Jennifer Kathryn Roloff (Harvard University (US)) -
49
Pile up mitigation in CMS jets and MET objects
We present tools developed by CMS for LHC Run II designed for pileup mitigation in the context of jets, MET, lepton isolation, and substructure tagging variables. Pileup mitigation techniques of "Pileup per particle ID" (PUPPI), and pileup jet identification are presented in detail along with the validation in data.
Speakers: Leonora Vesterbacka (Eidgenoessische Technische Hochschule Zuerich (CH)), Minna Leonora Vesterbacka (ETH Zürich)
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47
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10:30
Coffee
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Future Colliders
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50
ATLAS High Luminosity LHC studies
The High-Luminosity LHC aims to provide a total integrated luminosity of 3000/fb from proton-proton collisions at sqrt(s) = 14 TeV over the course of ~10 years, reaching instantaneous luminosities of up to L = 7.5 x 10^34/cm^2/s, corresponding to an average of 200 inelastic p-p collisions per bunch crossing (mu = 200). Fast simulation studies have been carried out to evaluate the prospects of various benchmark physics analyses to be performed using the upgraded ATLAS detector with the full HL-LHC dataset. The performance of the upgrade has been estimated in full simulation studies, assuming expected HL-LHC conditions. This talk will focus on the results of physics prospects studies for benchmark analyses involving in particular boosted hadronic objects (e.g. ttbar resonances, HH resonances (HH->bbbb) and dijet resonances), and on results of Jet/EtMiss studies of jet performance and pileup mitigation techniques that will be critical in HL-LHC analyses.
Speaker: Anna Kathryn Duncan (University of Glasgow (GB)) -
51
HL-LHC Developments from CMS
The prospects for boosted physics and jet substructure at the HL-LHC are presented, along with technical capabilities and updates to the detector that will assist in these measurements and searches.
Speaker: Julie Hogan (Brown University (US)) -
52
Jet reconstruction and boosted object tagging at the Compact Linear Collider
The Compact Linear Collider project envisages an electron-positron collider
with a low-energy stage at sqrt(s) = 380 GeV and an ultimate center-of-mass
reach up to 3 TeV. Detailed Monte Carlo simulation studies of the detector
are performed to optimize the design of the experiment and to understand
the physics potential. CLIC aims to meet the challenging requirements on
jet reconstruction performance with a highly granular calorimeter and
particle-flow reconstruction. In this contribution we present studies of the
jet reconstruction performance and new results on the capability of the
experiment to identify highly boosted objects.Speaker: Lars Rickard Strom (CERN) -
53
Simulations of detector response for multi-TeV physics at a 100 TeV pp collider
We discuss performance requirements for future detectors in the context of reconstruction of multi-TeV objects (single particles and jets) at a 100 TeV collider. A software framework based on a Geant4 simulation together with a realistic reconstruction of tracks and calorimeter clusters is presented. Using this framework, we discuss response and momentum resolution of the tracker and the calorimeter for single particles and hadronic jets in the energy range from 1 GeV to 30 TeV. In addition, lateral cell segmentation was studied by reconstructing substructure variables for jets at 10 and 20 TeV in transverse momentum.
Speaker: Sergei Chekanov (Argonne National Laboratory (US))
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50
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Public Event: Niagara Falls
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Public Event: Conference Dinner
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Summaries and Discussion
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Experiment SummarySpeaker: Christoph Falk Anders (Ruprecht-Karls-Universitaet Heidelberg)
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Summaries and Discussion
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