APS April 2022
US
We encourage ATLAS researchers, especially postdoc, graduate and undergraduate students from US universities, to give a presentation on their research during the APS 2022 "April" meeting from April 9-12.
The Physics Office (PO) will review your contribution. Please submit your draft video and draft slide or poster to this agenda page by Mar 21.
After addressing PO comments, each of you needs to upload final contribution to APS by Mar 24 (https://april.aps.org/virtual).
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BSM I
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1
Search for Dark Matter Produced in Association with a Dark Higgs Boson Decaying to two b-quarks Using full Run-2 data set from the ATLAS detector
A hypothetical dark Higgs boson was proposed in a dark matter (DM) model to explain the origin of mass in dark sector as well as to open up new annihilation channel relaxing the DM relic density constraint from cosmological observation. The search focusing on Majorana DM produced with a low mass dark Higgs boson decaying to two b-quarks is proposed and working in progress using the 139fb-1 of proton-proton collision data collected with ATLAS detector at √s=13 TeV.
The event selection and categorization are optimized based on the varying dark Higgs mass. Advanced jet clustering and boosted tagging techniques are applied to achieve higher efficiency and better signal over background ratio.
The analysis method and model interpretation strategy together with the result of expected sensitivity will be presented.Speaker: Qibin Liu (Tsung-Dao Lee Institute, Shanghai Jiao Tong Univ. (CN) & Univ. of Washington Seattle (US)) -
2
Search for Dark Matter produced in association with a Higgs boson decaying to a pair of b quarks and combination of Dark Matter search with 2HDM+$a$ with the ATLAS detector
Dark Matter (DM) searches are of great importantance to the LHC program. In this talk, I will first present a DM search using the Higgs boson as a portal. This search targets events that contain large missing transverse momentum and either two $b$-tagged small-radius jets or a single large-radius jet associated with two $b$-tagged sub-jets. No significant excess with respect to the SM prediction is observed. The results are then interpreted to set limits on two benchmark models with a second Higgs doublet and an additional heavy vector boson (2HDM+$Z^{ʹ}$) or a pseudoscalar singlet (2HDM+$a$), both of which provide a viable DM candidate. I will focus on how events are selected and categorized to enhance sensitivity to DM signals, and to help model the major backgrounds. Finally, I will also talk about the latest summary and combination of the searches for DM within the 2HDM+$a$ model.
Speaker: Jay Chan (University of Wisconsin Madison (US)) -
3
Search for dark mesons decaying to top and bottom quarks in 139 fb-1 of proton-proton collision data at √s = 13 TeV with the ATLAS detector at the LHC.
Extending the Standard Model (SM) with a new strongly coupled dark sector can generate models with both an experimentally accessible dark meson production mechanism and a viable dark matter candidate particle. A search for dark mesons is presented in an integrated luminosity of 139 $\mathrm{fb^{-1}}$ of proton-proton collision data at a center of mass energy of 13 TeV with the ATLAS detector at the Large Hadron Collider (LHC). In this model, dark pions are pair-produced and then decay to top-antitop or top-antibottom quark pairs. This talk describes the strategy and expected sensitivity of the all-hadronic channel of this search, with a signature of six or more jets and no additional missing transverse energy. Exclusion limits from this analysis are expected to provide new dedicated constraints on dark meson parameter space, exceeding existing limits derived from the reinterpretation of prior analyses.
Speaker: Galen Gledhill (University of Oregon (US)) -
4
Search for Heavy (pseudo)Higgs boson A/H produced in association with a top-antitop quark pair leading to the final state with four top quarks in $pp$ collisions at $\sqrt{s}=$ 13 TeV with the ATLAS detector
Four top-quark production, a rare process in the Standard Model (SM) with a cross-section around 12 fb, is one of the heaviest final states produced at the LHC, and it is naturally sensitive to physics beyond the Standard Model (BSM). A data excess is observed with twice of the expectation. A follow-up analysis is the search for Heavy (pseudo)Higgs boson A/H produced in association with a top-antitop quark pair leading to the final state with four top quarks. The data analyzed correspond to an integrated luminosity of 139 fb^-1. In this talk, the four top-quark decay final states containing either a pair of same-sign leptons or multi-lepton (SSML) are considered. To enhance the search sensitivity, a mass-parameterized BDT is introduced to discriminate the BSM signal against the irreducible SM four-top and other dominant SM backgrounds. Expected upper bounds on the production cross-section of A/H are derived in the mass range from 400 GeV to 1000 GeV.
Speaker: Meng-Ju Tsai (University of Michigan) -
5
Search for neutral long-lived particles decaying into displaced jets in the ATLAS calorimeter
New long-lived particles are a feature of many extensions to the Standard Model and may elude searches for promptly decaying particles. An analysis of data collected in $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector at the Large Hadron Collider is described, focusing on identifying signatures of jets produced by long-lived particles decaying to Standard Model fermions within the ATLAS calorimeter system. The analysis considers benchmark hidden sector models of neutral long-lived scalars with masses between 5 GeV and 475 GeV produced by decays of heavy mediators with masses between 60 GeV and 1000 GeV. Models of stealth supersymmetry, Higgs-portal baryogenesis, and dark photons are also considered. The results of this analysis are presented using the full Run 2 (2015-2018) data set, corresponding to an integrated luminosity of 139 fb$^{-1}$.
Speaker: Mason Proffitt (University of Washington (US)) -
6
Search for the pair production of vector-like quarks in the Wq+X fianl state with the full Run 2 ATLAS dataset
Vector-like quarks (VLQ) are predicted in many extensions to the
Standard Model (SM) as their vector-like nature allows them to extend
the SM while still being compatible with electroweak sector
measurements. Pair production of VLQ provides a model-independent
method of searching due to the QCD production of the particles. While
most searches have focused on VLQs that decay to an SM boson and a
third-generation quark, decays to light quarks have been largely
overlooked. This talk presents the expected results of a search for pair production of vector-like down quarks that decay into a leptonically decaying SM W
boson and a light quark, with the other VLQ decaying to a hadronically
decay boson and a light quark. The analysis uses boosted
boson identification and data-driven correction of the dominant W+jets
background prediction to improve sensitivity. Further, this analysis
extends the sensitivity of previous analysis done in Run 1 by increasing
the collision energy and the statistics by including the full Run 2
ATLAS dataset with an integrated luminosity of 139 $fb^{-1}$.Speaker: Evan Richard Van De Wall (Oklahoma State University (US))p.7: -140 fb^{-1} -> 140 fb^{-1}
Also: isn't the "good for physics" integrated luminosity for Run 2 = 139 fb^{-1}?
The latter comment applies to all "work in progress" plots...
p.8/9: dominate -> dominant
p.8: x-axis label on bottom is missing units.
p.11: Plots are missing sqrt(s), lumi.
Marc-André Pleier
on behalf of the
ATLAS Physics Office
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1
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BSM II
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7
Search for Generic Heavy Higgs Boson Using 13 TeV pp Collision Data at ATLAS
A search for a fermi-phobic heavy Higgs boson via the $pp \rightarrow W^{\pm}H \rightarrow W^{\pm}W^{\pm}W^{\mp}$ process with 139 fb$^{-1}$ of $pp$ collision data at $\sqrt{s}=13~\text{TeV}$ collected by the ATLAS detector is presented.
The heavy Higgs boson has potential dimension-6 effects in an effective field theory context, which can cause significant kinematic deviations from those predicted within the Standard Model. Events with two same-sign leptons ($e$ or $\mu$) in association with one large-R jet or two small-R jets with an invariant mass consistent with a hadronically decaying $W$-boson are analyzed to test for the presence of effects from new physics.Speaker: Yue Xu (Tsinghua University (CN))p.8: Please label the signal distributions with "ATLAS work in progress" or "ATLAS Simulation work in progress"
and add units on the x-axis. Add sqrt(s), lumi.
p.9: Add sqrt(s), lumi on expected limit plots.
p.10: "95% confidence level limits are set on" -> "95% confidence level expected limits are presented for"
p.18: Plot at center of slide is labeled "ATLAS" - should be "ATLAS work in progress". Add sqrt(s), lumi.Marc-André Pleier
on behalf of the
ATLAS Physics Office -
8
Search for Resonant and Non-Resonant VHH Production
Studies of Higgs boson pair production (hh) represent the next crucial step to constraining the Higgs sector and allow the chance to refine measurements of the Higgs boson self-coupling. While previous searches have focused on the hh production in the gluon-gluon fusion (ggF) and vector-boson fusion (VBF) modes, this analysis documents a new search, with 139 fb-1 of pp collisions at $\sqrt{s}$ = 13 TeV collected by the ATLAS detector in LHC Run 2, for di-Higgs production in the Vhh final-state. It searches for both resonant and non-resonant hh production, with only hh→$b\bar{b}b\bar{b}$ considered for simplicity, in association with a leptonically decaying vector boson (W or Z). While this process has a lower cross-section than ggF and VBF hh production, it offers a clean final state with relatively small backgrounds, due to the presence of leptons. The analysis benefits from small backgrounds and attempts to set limits for the first time on Vhh production. Analysis techniques and expected significance will be presented.
Speaker: Nicholas Graves Kyriacou (University of Michigan (US))
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7
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B and Top
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9
Identification of additional b-jets in the $t\bar{t}$ plus heavy flavor production with two leptons of the opposite sign in the final state using BDT for differential cross- section measurements
Top quark pair-production in association with one or two additional $b$-jets is one of the main backgrounds in the search for $t\bar{t}+H$ production, and in BSM physics searches involving top and bottom quarks in the final states. Precise measurement of $t\bar{t}+b$ and $t\bar{t}+bb$ differential cross sections will help to significantly reduce systematic and modeling uncertainties in future BSM searches and measurements of the top-Higgs coupling. A BDT that discriminates between $b$-jets which do or do not originate from top quarks decays has been developed in the opposite-sign dilepton channel. The method has higher purity compared to the existing method based on the angular distributions between $b$-jets and leptons. Preliminary results show that with the new method we can accurately measure the $p_{T}$ spectra of $b$-jets from top quark decays and of the leading additional $b$-jet up to 400 GeV, and the sub-leading additional $b$-jets $p_{T}$ up to 300 GeV. The analysis uses LHC proton-proton collision data at the center-of-mass energy $\sqrt{s}=13$ TeV with an integrated luminosity of 139 fb$^{-1}$ collected with the ATLAS detector in 2015-2018.
Speaker: Egor Antipov (Oklahoma State University (US))p.2: Please add references for graphics not created by you.
p.5,6: Please add units on x-axis where applicable (mass variables).
Marc-André Pleier
on behalf of the
ATLAS Physics Office==============================================================================
Egor:
UPD: implemented the changes, uploaded the presentations and video files named as requested by APS. -
10
Measurement of the $CP$-violating phase $\phi_s$ in $B_s^0\rightarrow J/\psi\phi$ decays in ATLAS at $13~\mathrm{TeV}$
A measurement of the $B_s^0\rightarrow J/\psi\phi$ decay parameters using $80~\mathrm{fb}^{-1}$ of integrated luminosity collected with the ATLAS detector from $13~\mathrm{TeV}$ proton-proton collisions at the LHC is presented. The measured parameters include the $\textit{CP}$-violating phase $\phi_s$, the width difference $\Delta\Gamma_s$ between the $B_s^0$ meson mass eigenstates and the average decay width $\Gamma_s$. The values measured for the physical parameters are combined with those from $19.2~\mathrm{fb}^{-1}$ of $7~\mathrm{TeV}$ and $8~\mathrm{TeV}$ data, leading to the following:
\begin{equation}
\phi_s=-0.087\pm0.036~(\mathrm{stat.})\pm0.021~(\mathrm{syst.})~\mathrm{rad}
\end{equation}
\begin{equation}
\Delta\Gamma_s=0.0657\pm0.0043~(\mathrm{stat.})\pm0.0037~(\mathrm{syst.})~\mathrm{ps}^{-1}
\end{equation}
\begin{equation}
\Gamma_s=0.6703\pm0.0014~(\mathrm{stat.})\pm0.0018~(\mathrm{syst.})~\mathrm{ps}^{-1}
\end{equation}
Results for $\phi_s$ and $\Delta\Gamma_s$ are also presented as $68\%$ confidence level contours in the $\phi_s-\Delta\Gamma_s$ plane. Furthermore, the transversity amplitudes and corresponding strong phases are measured. $\phi_s$ and $\Delta\Gamma_s$ measurements are in agreement with the Standard Model predictions.Speaker: Easwar Anand Narayanan (University of New Mexico (US)) -
11
Studies of C-jet spectra in various Flavor Schemes for $t\bar{t}+c$ cross section measurement
A comparison of three flavor scheme, four flavor scheme and five flavor scheme has been performed using top quark pair-production with additional charm jet $(t\bar{t}+c)$ events simulated by MadGraph and showered by Pythia8. Spectra of additional c-jets that do not originate from the top quark decay are compared in the three schemes. These studies are motivated by the upcoming $t\bar{t}+c$ jets cross section measurement. No significant differences in spectra of additional c-jets are observed in the different flavor schemes.
Speaker: Calvin Ainsworth (Oklahoma State University (US))
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9
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Higgs
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12
Search for Higgs Boson Pair Production in the Multi-lepton Final State Using Proton-Proton Collision Data at $\sqrt{s} =13$ TeV from the ATLAS Detector
This talk will present a search strategy for Higgs boson pair-production in final states with three electrons or muons. The analysis is performed using an integrated luminosity of 139 fb$^{-1}$ of $pp$ collision at $\sqrt{s}= 13$ TeV collected by the ATLAS detector at the LHC. There are many decay modes of Higgs boson pairs that have low branching ratios, and many of these are not covered by dedicated analyses. Some example modes of particular interest for a three lepton final state are WWWW, WW$\tau \tau$, $\tau \tau \tau \tau$, etc. This talk presents the development of a multivariate strategy (boosted decision trees) and current work on background estimation methods and statistical analysis.
Speaker: Santosh Parajuli (Southern Methodist University (US)) -
13
Combination of searches for resonant and non-resonant Higgs boson pair production in the bbyy, bb𝜏𝜏 and bbbb decay channels using pp collisions at √s= 13 TeV with the ATLAS detectors = 13 TeV with the ATLAS detector
A combination of searches for Higgs boson pair production is performed using up to 139 fb$^{-1}$ of proton-proton collision data at a center-of-mass energy $\sqrt{s} = 13$ TeV recorded with the ATLAS detector at the LHC. The combination exploits three analyses searching for $HH$ decays to $bb\gamma\gamma$, $bb\tau\tau$ and $bbbb$. Results are interpreted in the context of non-resonant and resonant Higgs boson pair production scenarios. In the non-resonant interpretation, upper limits are set on the Higgs boson pair production cross-section and on the self-coupling modifier $\kappa_{\lambda}$. In the resonant interpretation, upper limits are set on the Higgs boson pair production cross-section as a function of the heavy resonance mass.
Speaker: Alkaid Cheng (University of Wisconsin Madison (US))My general comment is that for any table or figure that you take from a reference, the reference should be added close to the table/figure on the same slides. If the table/figure is made by yourself, then please add a label "ATLAS Work in progress" or "ATLAS Simulation Work in progress". The "Internal" label should be replaced with "Work in progress".
Zhiqing for the ATLAS Physics Office
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14
Measuring Diphoton Production in Association with Heavy Flavor with the ATLAS Detector
This unique analysis investigates the production of two photons in conjunction with heavy flavor quarks using the ATLAS detector at the Large Hadron Collider at CERN using the full Run 2 dataset with a center-of-mass energy of $\sqrt{s}= 13$ TeV. The $\gamma\gamma$ + heavy flavor jets process is a dominant background in at least two important analyses: the $HH\rightarrow\gamma\gamma bb$ process, which provides a direct probe of Electroweak Symmetry Breaking due to observation of the Higgs boson self-coupling and the $t\bar{t}H\rightarrow\gamma\gamma$ process, which is important for measuring the Yukawa coupling between the Higgs and top quark. Despite its importance, $\gamma\gamma$ + heavy flavor jets process has never generically been measured before, nor is there any direct prediction in literature. A template fit will be implemented to the jet flavor-tagging discriminant to extract the signal to measure the components of heavy flavor in $\gamma\gamma + jets$. The measurements will be made in the single-jet or multi-jet categories that are a combination of b-, c-, and light-flavor jets (bb, bc, bl, etc.). Preliminary sensitivity estimates will be shown.
Speaker: Brianna Dwyer (Northern Illinois University (US)) -
15
Combination of Searches for HH Production with ATLAS Run 2 Data
Searches for di-Higgs production are some of the most exciting new results at the LHC. This talk will present the latest ATLAS HH combination results with the full Run 2 dataset of 139/fb at $\sqrt{s}=13$ TeV. By combining results from three different complementary search channels, bbγγ, bbττ, and bbbb, the HH combination has high sensitivity in both non-resonant and resonant interpretations.
In the non-resonant interpretation, bbγγ and bbττ channels are combined to produce limits on the Standard Model (SM) HH production cross-section and the Higgs boson self-coupling. Although no evidence for a signal was observed, the observed (expected) upper limits on SM HH production cross-section at 95% confidence level are 91.44 fb (92.10 fb). The combination of both channels also provides strong observed (expected) limits on Higgs self-coupling modifier, $𝜅_{𝜆}$ , between $−1.0 ≤ 𝜅_{𝜆} ≤ 6.6$ ($−1.2 ≤ 𝜅_𝜆 ≤ 7.2$).
For the resonant interpretation, bbγγ, bbττ, and bbbb, are combined to search for a heavy scalar decaying into two Higgs bosons with masses between 251 GeV - 3 TeV. Upper limits on the observed (expected) production cross-section are set ranging between 1.1 and 595 fb (1.2 and 393 fb).
Speaker: Jannicke Pearkes (SLAC National Accelerator Laboratory (US)) -
16
Measurement of the Higgs boson production cross section using the H -> tau tau process in Run 2 ATLAS data
A measurement of the Higgs boson cross section using H -> tau tau decays is performed, with the result split into 4 production modes, with both hadronic and semi-hadronic decays considered. Data was taken by the ATLAS detector during Run 2 of CERN's Large Hadron Collider, with a center-of-mass energy of 13 TeV, resulting in 139 fb^{-1} of proton-proton collision data. Full unblinded results are shown. Special attention is paid to the associated top quark pair production mode, including a proposed differential cross section measurement of the transverse momentum of the Higgs boson using a neural network to improve the resolution.
Speaker: Marc Tost (University of Texas at Austin (US)) -
17
Measurement prospects for di-Higgs production in the HH->bbyy channel with the ATLAS experiment at the HL-LHC
We present a prospect study on di-Higgs production in the $HH \rightarrow b\bar{b}\gamma\gamma$ decay channel with the ATLAS experiment at the High Luminosity LHC (HL-LHC). The results are obtained by extrapolating the results from the Run 2 measurement, with 139 fb$^{-1}$ of data at a center-of-mass energy of 13 TeV, to the conditions expected at the HL-LHC. While there is no sign of di-Higgs production with the current LHC dataset, the much higher luminosity (3000 fb$^{-1}$) and energy (14 TeV) at the HL-LHC will enable a much better measurement of this important process. We describe in detail the extrapolation process and assumptions, and multiple scenarios for the treatment of systematic uncertainties at the HL-LHC are considered. Under the baseline systematic uncertainty scenario, the extrapolated precision on the Standard Model di-Higgs signal strength measurement is 50%, corresponding to a significance of 2.2$\sigma$. The extrapolated precision on a measurement of $\kappa_\lambda$, the trilinear Higgs boson self-coupling modifier, is [0.3, 1.9].
Speaker: Alex Zeng Wang (University of Wisconsin Madison (US))It is not clear to me which tables/plots on your slides are from the reference given on page 4. All the plots that have a "Preliminary" label need a reference to be shown close to the plots. The "Internal" label must be replaced with "Work in progress" or the corresponding approved material with a reference.
Zhiqing for the ATLAS Physics Office
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12
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Instrumentation I
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18
Construction and Testing of the first 12 sMDT Chambers at University of Michigan for the ATLAS HL-LHC upgrade
The Large Hadron Collider (LHC) will be upgraded to increase its luminosity by a factor of 7.5 relative to the design luminosity. The ATLAS detector will undergo a major upgrade to fully explore the physics opportunities provided by the upgraded LHC. In order to optimize trigger efficiencies at the High-Luminosity LHC (HL-LHC), the Muon Spectrometer will be upgraded by replacing the MDT (Monitored Drift Tube) chambers by smaller-diameter MDT (sMDT) chambers and additional thin-gap RPC (Resistive Plate Chamber) trigger chambers in the barrel inner station. The University of Michigan ATLAS group is responsible for building 50% of the sMDT chambers. I will report on the construction and testing of the first 12 sMDT chambers built at the University of Michigan in 2021. Precision measurements and testing procedures will be described and the chamber precision and performance results will be presented.
Speaker: Neal Anderson (The University of Michigan) -
19
Test beam and performance study of ATLAS New Small Wheel small-strip Thin Gap Chamber
The Large Hadron Collider is expected to reach an instantaneous luminosity of $5-7.5\times10^{34}cm^{-2}s^{-1}$ towards high-luminosity runs in the future. The ATLAS Phase-Ⅰ upgrade plans to replace the present innermost station of Muon Spectrometer in the forward region, Small Wheels, with the New Small Wheel (NSW) detector system in order to improve Level-1 muon trigger selectivity and maintain good muon tracking capability under high background rate. The NSW features two gaseous detector technologies, Micro Mesh Gaseous Structures (MM) and small-strip Thin Gap Chambers (sTGC), with 2.4 million readout channels and a total surface area of more than $2,500m^2$. Both detectors have trigger and precision tracking capabilities.
The new Gamma Irradiation Facility (GIF++) located at the H4 beam line of SPS at CERN is a unique place where high energy muon and pion beams are combined with a 14TBq $^{137}$Cesium source to test the detector tracking ability in a high background rate environment. One fully integrated sTGC quadruplet was tested at GIF++ in a muon beam during Oct-Nov 2021. This is the first time a test beam is performed on the sTGC with final version electronics and using the final DAQ (data acquisition) system. In this talk we present the test beam setup and performance results, namely efficiency and resolution at different track inclination and photon background rates. Studies of the impact of different electronics configuration will also be presented.Speaker: Xinmeng Ye (University of Michigan (US) / University of Science and Technology of China (CN)) -
20
Alignment system of the muon end-cap new small wheels
The muon spectrometer of the ATLAS detector at the LHC consists of thousands of muon precision chambers. Precise muon track reconstruction is crucial in order to achieve the physics goals of the ATLAS experiment, but attaining the required level of precision is not trivial due to the size and nature of the muon detectors. To reach the 80 microns precision needed to obtain a 10% precision on 1 TeV-momentum muon, an optical-based alignment system has been designed and installed on the muon spectrometer. In this talk I will describe this alignment system, which consists of thousands of coupled light sources and optical sensors, focusing on the upgrade and commissioning of the system for the New Small Wheels, a brand-new addition to the muon end-cap spectrometer.
Speaker: Camila Pazos (Tufts University (US)) -
21
Performance of sMDT chambers for the HL-LHC ATLAS muon spectrometer upgrade
New small Monitored Drift Tube (sMDT) chambers were developed by the Max Planck Institute (MPI) for the ATLAS muon spectrometer upgrade. The smaller tube size allows sMDT chambers to cope with the increased luminosity of the High Luminosity LHC (HL-LHC) and make space for additional Resistive Plate Chamber (RPC) layers. The University of Michigan will construct 48 sMDT chambers containing over 23,000 drift tubes by 2024. This talk will report on the methodology used to reconstruct cosmic-ray muon tracks in the sMDT chambers assembled at the University of Michigan, including a Geant4 simulation of the sMDT chambers. Chamber commissioning test results using cosmic-ray muons are presented, including noise rate, efficiency, and resolution studies.
Speaker: Kevin Michael Nelson (University of Michigan (US)) -
22
sMDT Production and Testing at UM for the HL-LHC ATLAS Muon Spectrometer Upgrade
To accommodate the high trigger-rate conditions at the High Luminosity Large Hadron Collider (HL-LHC) in Run 4 and onwards, the Monitoring Drift Tube (MDT) chambers in the inner barrel layer of the ATLAS muon spectrometer will be replaced with new small-diameter MDTs. The upgrade will allow for better muon tracking resolution and for the installation of new Resistive Plate Chambers (RPCs) to maintain a high trigger efficiency. To ensure consistency and quality in each individual drift tube, a detailed construction and testing process is developed and used for the sMDT production process at the University of Michigan (UM) and Michigan State University (MSU). A major effort in tube production was made by UM during 2021 to ensure a timely sMDT chamber construction schedule. In this talk, I will present the cumulative testing results between the two sites which show an excellent production year in quality and quantity.
Speaker: Andy Chen (University of Michigan (US)) -
23
sTGC Trigger Chain Cosmic Ray Test
The New Small Wheel (NSW) phase-I upgrade is an extremely challenging project for high-luminosity LHC operations to improve both tracking and trigger capability of the ATLAS muon spectrometer for discoveries at the LHC.
NSW consists of two types of new detectors, the small-strip Thin Gap Chambers (sTGCs) and the MicroMegas (MM) chambers, both are capable of precision tracking and fast triggering. This is the first time such new detectors were built at large scales. It has taken 10 years to design and build the NSW. Intensive integration and commissioning were carried out in the past three years. I will report the sTGC integration and commissioning work, including the cosmic ray test. I will describe in detail about how the sTGC trigger chain works and present some important cosmic test results to demonstrate the sTGC level-0 trigger performance.
Speaker: Man Yuan (University of Michigan (US))
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18
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Instrumentation II
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24
Development and Testing of the AMACStar ASIC at Penn for the ATLAS ITk Detector
In preparation for the high-luminosity LHC (HL-LHC), the ATLAS detector will be upgraded with a new silicon-strip charged-particle tracking detector (ITk strip detector) to satisfy the radiation, granularity and timing requirements. The AMACStar (Autonomous Monitor and Control) is one of three ITk application-specific integrated circuits (ASICs). It is designed to monitor and control temperatures, voltages, and currents in the detector modules. This is an essential function for the ITk detector; the ASIC can autonomously (and quickly) identify hazards in the detector modules, controlling and preventing them from spreading.
The ITk ASICs are produced on wafers containing several hundred chips. In order to ensure that each AMACStar chip works and performs as expected, a comprehensive probe-station testing software and procedure have been developed. This setup tests the digital and analog functionality of each AMACStar to be installed in the ITk modules. I will present the probe-station setup and probing results of pre-production AMACStar chips.
Speaker: Thomas Christopher Gosart (University of Pennsylvania (US)) -
25
ATLAS Tau Trigger Algorithm for Global Trigger using Full Granularity Data
The High-Luminosity Large Hadron Collider (HL-LHC) is expected to deliver 10 times the integrated luminosity as the previous three runs combined, with approximately 200 inelastic collisions per bunch crossing. This large increase in pileup imposes significant challenges on the ATLAS Trigger and Data Acquisition system hardware electronics. To meet this challenge, the Global Trigger is designed to accept full-granularity data from the calorimeter and muon systems at 40 MHz to perform offline-like trigger algorithms. Hadronically decaying tau leptons play a key role in Standard Model (SM) measurements and searches beyond the SM, but taus are challenging to trigger on due to their resemblance to QCD jets. A window-based tau trigger algorithm is being developed for the Global Trigger firmware using system Verilog. The presentation will focus on the progress on both software and the firmware aspects of this algorithm development as part of the ATLAS HL-LHC upgrade.
Speaker: Anni Xiong (University of Oregon (US)) -
26
ATLAS Global Tau Trigger Performance Study for Run 4
Tau decays are notoriously difficult to detect because many particles decay with a similar signature. When searching for taus, capturing data from tau-lookalikes has been an ongoing problem, and previous global tau trigger algorithms have only had access to coarse granularity data from the calorimeters. The upgrade of the ATLAS Trigger and Data Acquisition system for the High-Luminosity Large Hadron Collider will provide high-granularity calorimeter information, offering enhanced performance required for operation during Run 4 (with 200 interactions per bunch crossing). Here we present the expected tau trigger performance, including the efficiency and background rejection.
Speaker: Katherine Rose Kaylegian-Starkey (University of Oregon (US)) -
27
CSM FPGA Irradiation Test at LANSCE for the HL-LHC ATLAS Muon Spectrometer Upgrade
The increased radiation environment and data rate for the High Luminosity Large Hadron Collider (HL-LHC) require upgrades to the readout electronics for the Muon Spectrometer (MS) electronics. In this talk, I will present ongoing irradiation studies of a custom-built front-end electronics board, the chamber service module (CSM), which is responsible for multiplexing data read out from on-detector electronics as well as passing configuration information to them. An important component of the CSM is a Field-programmable gate array (FPGA), specifically using the FPGA Artix7 xc7a35T, which is responsible for fanout of configuration and control information for 18 mezzanine cards. The Artix-7 is a commercial component with a history of meeting our radiation specifications. The specific model used in the CSM was tested in a radiation hard environment with an average flux 103 higher than ATLAS (6.02E+3 n/$cm^{2}$/s vs 1.3E+6 n/$cm^{2}$/s). Preliminary results show that the LANSCE Single Event Upset (SEU) test approximately had 3 years of ATLAS in comparison with ~ 1.9E+11n/$cm^{2}$/y fluence (MDT CSM Requirement) and accumulated 18 SEU errors for two boards.
Speaker: Jem Aizen Mendiola Guhit (University of Michigan (US)) -
28
Electrical characterisation of stave prototypes for the ATLAS ITk Upgrade
The ATLAS experiment is currently preparing for an upgrade of the inner tracking detector for High-Luminosity LHC operation, scheduled to start in 2027. The new detector, known as the Inner Tracker or ITk, employs an all-silicon design with five inner Pixel layers and four outer Strip layers. The staves are the building blocks of the ITk Strip barrel layers. Each stave consists of a low-mass support structure which hosts the common electrical, optical and cooling services as well as 28 silicon modules, 14 on each side. Two prototype electrical long-strip staves have been assembled at BNL.In this talk, we will present the deliverables of this prototyping phase highlighting the improvent of the stave layout and the results on the most recent stave.
Speaker: Francesca Capocasa (Brandeis University (US)) -
29
Hough Transform pattern recognition for track finding at the ATLAS experiment at the LHC
We are exploring Hough Transform (HT) algorithms in FPGAs to identify charged particle trajectories in the ATLAS detector at the HL-LHC. The Inner Detector of the ATLAS experiment measures the trajectories of charged particles in a uniform magnetic field. Our approach is to perform the Hough transformation pattern identification in two steps. The “first-stage” HT uses parameter space in phi0 and q/pT using hits from the semiconductor tracker and identifies those that are consistent with being from the same track. We evaluate adding a second HT step using eta-z0 track coordinate plane, that processes hits identified from roads in the first stage. A working firmware prototype for FPGAs is designed. The performance of this second stage HT is measured as the efficiency and rejection of MC simulations and is presented here, along with an estimation of the resources required of the firmware.
Speaker: Natalie Harrison (Ohio State University) -
30
Thermal and electrical performance tests of ATLAS silicon strip detector modules at BNL
The inner tracking detector of the ATLAS experiment at CERN is currently preparing for an upgrade to operate in the High Luminosity LHC, scheduled for the late 2020s. A complete replacement of the existing Inner Detector of ATLAS is required to cope with the expected luminosity and radiation damage. The all-silicon Inner Tracker (ITk) design under construction composes a mixture of Pixel and Strips layers. At the core of the strip, barrel detector is the stave, thermo-mechanical support structures, each of which hosts 28 silicon modules. A thorough characterization of the modules before the assembly on each stave is critical; thus, each module has to undergo electrical and thermal quality control (QC) testing between module production and stave assembly. The modules are thermal cycled ten times between -35C and +40C. This talk will discuss the thermal and electrical performance of the US testing setup, focusing on the difficulties encountered to meet the QC requirements. It will also give an overview of the results obtained by analyzing the first batch of produced modules during pre-production.
Speaker: Punit Sharma (University of Iowa (US))
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24
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ML
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31
Point Cloud Deep Learning Methods for Pion Reconstruction in the ATLAS Detector
Reconstructing the type and energy of isolated pions from the ATLAS calorimeters is a key step in hadronic reconstruction. The existing methods were optimized early in the experiment lifetime. We recently showed that image-based deep learning can significantly improve the performance over these traditional techniques. This note presents an extension of that work using point cloud methods that do not require calorimeter clusters to be projected onto a fixed and regular grid. Instead, we use transformer, deep sets, and graph neural network architectures to process calorimeter clusters as point clouds. We demonstrate the performance of these new approaches as an important step towards a full deep learning-based low-level hadronic reconstruction.
Speaker: Mariel Pettee (Lawrence Berkeley National Lab. (US)) -
32
Quark and Gluon Tagging Calibration with the ATLAS
The separation of quark and gluon initiated jets(q/g jets) is crucial to enhance the reach of many new physics searches at the ATLAS experiment in the Large Hadron Collider. A tagger serving as a tool to distinguish quark and gluon jets is developed based on the Boosted Decision Tree using charged-particle track observables associated with the jet. However, quark-versus-gluon jet tagging is difficult to be calibrated due to the difficulty of the hadronization modeling. To improve the performance of the tagger, a "matrix method" is applied to extract the q/g distributions to obtain a scale factor which is a ratio between data and Monte Carlo. The data taken from 2015 to 2018 with an integrated luminosity of 139.0 fb-1 are used to calibrate the tagger with two control samples to select dijet and gamma+jet events, providing various gluon and quark enriched samples. In this talk, the latest results of calibration and systematic uncertainties will be presented.
Speaker: Haoran Zhao (University of Washington (US))p.1: Only the speaker name should be listed as author, and optionally the student can indicate the name of the direct supervisor(s).
p.4: Please add references for graphics not created by you.
p.10: Is your Ntrack distribution in the bottom plot turning negative?
Left plots are missing x-axis labels.
Marc-André Pleier
on behalf of the
ATLAS Physics Office
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31
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SM I
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33
Study of W^±Z longitudinal-longitudinal interactions ($W_0^{\pm} Z_0$) with Full Leptonic Final States ($W^{\pm} Z \rightarrow l^{\pm} νl^{\pm} l^{\mp}$)
In the Standard Model of particle physics, the spontaneous symmetry breaking of the complex Higgs field gives rise to the massive Higgs boson and three Goldstone bosons, which represent the longitudinal degrees of freedom of the $W^{\pm}$ and $Z$ bosons. It is therefore critical to study the interactions of longitudinally-polarized $W^{\pm}$ and $Z$ bosons ($W^{\pm}_0$ and $Z_0$). Here, we present the first such analysis, in inclusive fully-leptonic final states ($W^{\pm} Z→l^± νl^± l^∓$) with 139 fb$^{-1}$ of proton-proton collision data recorded with the ATLAS detector at a 13 TeV of center of mass energy. We use kinematic variables like $p_T^Z$ and $p_T^{W^{\pm}Z}$ to enhance the $W^{\pm}_0Z_0$ contribution. The so called radiation amplitude zero effect also enhances the $W^{\pm}_0Z_0$ contribution in the central region ($\cos\theta_V$ ~ 0, where $\theta_V$ is the scattering angle of the $W^{\pm}$ or $Z$ boson in the parton center-of-mass frame). A multivariate variable is developed to separate the longitudinal-longitudinal polarization from other polarizations. A template fit will be performed to extract polarization fractions.
Speaker: Prachi Atmasiddha (University of Michigan, Ann Arbor)All the materials including tables taken from a reference need to have the reference to be shown close to the material on the slides. Those made by yourself using ATLAS data/MC/software should be labelled with "ATLAS Work in progress" or "ATLAS Simulation Work in progress".
Zhiqing for the ATLAS Physics Office
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34
Measurement of collinear W boson emission off high transverse momentum jets using full Run-2 data.
The production of a single electroweak vector boson in association with jets (V+jets) is one of the fundamental processes at the Large Hadron Collider (LHC) experiment. The leptonic decay modes of this process provides a clean experimental signature for measuring the electroweak sector of the Standard Model and the perturbative QCD accuracy in multi-jets final states.
In the talk, we will focus on the differential measurement of single W decaying to an electron or muon from a high transverse momentum jet with small angular separation, the so called collinear W+jets production. This measurement makes use of the LHC full Run-2 proton-proton collision datasets, corresponding to an integrated luminosity of 139.0 fb-1 . The data is compared against newly develop state-of-the-art multi-jet merged setups accurate to next-to-leading order in the strong and weak coupling constants. The details of the generator configurations and their CPU costs will be discussed, and unfolded kinematic distributions at particle level in the collinear W+jets phase-space will be compared with the measured data cross sections.
Speaker: Yuzhan Zhao (University of California,Santa Cruz (US)) -
35
Study of WWZ tri-boson production at ATLAS
The Standard Model predicts self interactions between gauge bosons, including triple gauge boson couplings (TGC) and quartic gauge boson couplings (QGC). In addition, the interactions between the Higgs boson and gauge bosons are also of interest. In ATLAS group, events with four leptons (electrons or muons) in the final state are used to search for the production of WWZ -> lvlvll. The total luminosity used is 139 fb-1 at sqrt{s}=13 TeV. Events are further divided into three categories based on the invariant mass and the flavor of the two leptons from the decays of the two W bosons to increase the search sensitivity. A multivariate variable is further developed to increase the separation between the signal and background. I will present optimization on event selection and search sensitivity studies using simulated Monte Carlo events.
Speaker: Zhichen Wang (University of Michigan (US))
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33
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SM II
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36
Measurement of four-jet production in the ATLAS experiment
Measurements of multi-jet cross-section ratios are presented.
The measured quantities are the ratio of the four-jet and three-jet
cross-sections and the ratio of the four-jet and two-jet cross-sections.
The data were collected with the ATLAS detector in proton-proton
collisions at a center of mass energy of 13 TeV during 2015-2018.
The results are presented as a function of the transverse jet momentum.
Predictions from different Monte Carlo event generators are compared
to the data.Speaker: Zahra Farazpay (Louisiana Tech University (US)) -
37
Cross section measurement of associated $J/\psi+W^{\pm}$ production with the ATLAS detector
The cross-sections of prompt and non-prompt production of $J/\psi+W^{\pm}$ are being measured by the ATLAS Collaboration using the $139~\textrm{fb}^{-1}$ Run II 13 TeV $pp$ collision data set. The prompt production of $J/\psi$ associated with a $W^{\pm}$, where both particles are produced in a single parton-parton interaction, provides constraints on models of non-relativistic QCD, especially in the realm of heavy quarkonia production. The measurement is an all-leptonic final state with $J/\psi\rightarrow\mu^+\mu^-$ and $W^{\pm}\rightarrow\ell^{\pm}\nu$, and it is performed differentially in $J/\psi$ transverse momentum and rapidity. Finally, the non-prompt measurement allows for the study of top production and $b$-quark fragmentation.
Speaker: Charles Burton (University of Texas at Austin (US)) -
38
Measurement of Z plus Heavy Flavor Jets Differential Cross Section with Full Run-2 ATLAS data
Measurements of the production rate of Z bosons in association with heavy quarks provide sensitive tests of perturbative quantum chromodynamics (pQCD) predictions, which are made at next-to-leading-order (NLO) accuracy using either a 4-flavor number scheme (4FNS) or 5-flavor number scheme (5FNS). In the 4FNS, b-quarks are not present in the parton distribution functions (PDFs) and only appear as a product of gluon splitting ($g\to bb$). In the 5FNS, on the other hand, a (massless) b-quark PDF is included. A previous analysis studying $Z\to ee/\mu\mu$ + b-jet events using 2015 & 2016 data showed that the 5FNS predictions match the data well, while the 4FNS predictions underestimate the data. The uncertainties are substantial, however. In our analysis we are attempting to further investigate these results by also including Z + c-jet events and looking at the combined “heavy-flavor” (b+c) region to reduce uncertainties. We are also updating the 2015-2016 results with 140 $\rm{fb}^{−1}$ (up from 35.6 $\rm{fb}^{−1}$) of ATLAS Run-2 data at $\sqrt(s)= 13$ TeV. This is still a work in progress, but important milestones will be presented.
Speaker: Alec Drobac (Tufts University (US))
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36
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SUSY
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39
Search for B-L RPV Supersymmetry Through Stop Pair Production in Final States with 2 b-jets and 2 Leptons Using the Run 2 Data from the ATLAS Detector
Supersymmetry is a natural solution to many phenomena left unexplained by the Standard Model, such as the hierarchy problem that arises due to quantum corrections to the Higgs boson mass. Models which allow for R-parity violation (RPV) are favored by recent lepton flavor anomalies and can provide insight into the neutrino mixing hierarchy. The direct pair production of the stop, the supersymmetric partner to the top quark, is of particular interest due its sizable production cross section at the LHC, which allows for searches at the TeV scale. We present a search for stop pair production, with each stop decaying via an RPV coupling to a b quark and a charged lepton. This final state with two oppositely-charged leptons and two b-quark-initiated jets allows for a high reconstruction efficiency. The reconstructed mass asymmetry is used to properly pair candidate jets and leptons to form stop candidates, enabling powerful background rejection. In this talk, I will discuss the current work on the B-L RPV stop analysis using the full Run 2 dataset collected with the ATLAS detector.
Speaker: Mx James Heinlein (University of Pennsylvania (US)) -
40
Search for Higgsinos Decaying into Semi-Long-Lived Charged Particles in the ATLAS Detector with LHC Run 2 Data
Higgsinos with compressed mass spectra and masses near the electroweak scale are highly motivated by naturalness considerations and consistent with cosmological evidence, yet still poorly constrained by the LHC. This search will focus on the neutralino mass splitting $Δm=m_{{\widetilde{χ}}_2^0}-m_{{\widetilde{χ}}_1^0}$, in the region of 0.3~2 GeV, which has not been covered by ATLAS analyses to date. The current limit set by LEP only excludes up to $m_{{\widetilde{χ}}_1}$~95 GeV. We plan to probe higher masses by identifying the track corresponding to a soft charged pion from the slightly long-lived (with cτ ~1 mm) higgsino decay. The analysis will look for the associated production of higgsino-like chargino (${\widetilde{χ}}_1^\pm$) and neutralino (${\widetilde{χ}}_2^0$) in LHC pp collisions using the ATLAS Run-2 dataset. The event signature includes a high momentum jet from initial state radiation, and a displaced pion $π^\pm$ from ${\widetilde{χ}}_1^\pm/{\widetilde{χ}}_2^0$ decay aligned with significant missing energy in the transverse plane. Using Monte Carlo simulation, I will present a preliminary sensitivity estimate for $m_{{\widetilde{χ}}_1^0}$~150 GeV, and suppression strategy against backgrounds from semi-long-lived particles using track energy loss and secondary vertex reconstruction.
Speaker: Sicong Lu (University of Pennsylvania (US))p.3: Please do not cover the ATLAS plot label with your own labelling.
p.4/5: Please add references for the plots shown.
p.6: Please add "ATLAS work in progress", sqrt(s) on the right plot.
p.7: Please add "ATLAS work in progress", sqrt(s) on the plots.
p.8: Please add "ATLAS work in progress", sqrt(s), lumi for the table.
p.11,13: Plots missing ATLAS labelling, see above. Bottom plot misses axis labels.
p.12: Add reference for table.Marc-André Pleier
on behalf of the
ATLAS Physics Office
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39
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Poster
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41
(Withdraw) Predicting the missing transverse momentum trigger rate at ATLAS with machine learning
One of the challenges of the ATLAS missing transverse momentum trigger is understanding how the trigger rate will evolve with the number of proton collisions per bunch crossing, or pileup. In the past, the data have been fit to parametric functions and extrapolated to higher pileup values. In this poster, we present a new technique using machine learning regression models to describe the trigger rate, and allow for extrapolation to higher values of pileup.
Speaker: Chandler Baker (Westmont College) -
42
Investigating Gluon Fusion as New Channel to Search for Dark Matter
In Higgs portal models, it is predicted that the Higgs boson could decay into dark matter particles. We may be able to detect these processes with the ATLAS detector, located at the Large Hadron Collider in Geneva Switzerland. There are many different production modes of the Higgs boson that could be used in a search for these Higgs boson to invisible decays, and when used together they provide our best chance at discovering new physics. Previous work has been done with vector-boson fusion production (VBF), but gluon fusion (ggF) production has a larger cross section, making it a promising candidate to aid in the search. Therefore, we are investigating the feasibility of using a MET+photon trigger at ATLAS to provide sensitivity to ggF production of the Higgs boson; Large MET is characteristic of any Higgs boson to invisible decay, and the photon requirement would provide sensitivity to $H \rightarrow \gamma\gamma_{d}$ decays, where $\gamma_{d}$ is a dark photon.
Speaker: Connor Harrison Menzel (University of Pittsburgh (US)) -
43
ATLAS NSW sTGC Readout Electronic Integration and Commissioning
The most challenging ATLAS Phase I upgrade project during Long Shutdown 2 (2019-2021) is the New Small-Wheel (NSW) for Muon Spectrometer. The main purpose of the NSW upgrade is to improve the performance of muon triggering and precision tracking for the High-Luminosity Large-Hadron-Collider (HL-LHC), which will deliver 3,000 fb-1 of data at √s = 14 TeV. The NSW will feature two new detector technologies: Resistive Micromegas (MM) and small-strip Thin Gap Chambers (sTGC), with MM playing the role of a primary tracking detector and sTGC as a primary trigger. To retain the good precision tracking capabilities in the high background environment of the HL-LHC, each sTGC plane must achieve a spatial resolution better than 100 μm to allow reconstruction of the Level-1 trigger track segments with an angular resolution of approximately 1mrad. This presentation focuses on the electronic readout integration and readout commissioning of sTGC detectors at CERN, both in the integration phase and for the two, separate, NSW commissionings, including a summary of the progress achieved, the problems encountered, and adapted solutions.
Speaker: Nicholas Graves Kyriacou (University of Michigan (US)) -
44
Commissioning of the Phase-1 BIS78 pilot project for Phase-2 upgrade of the ATLAS muon spectrometer
The Monitored Drift Tube (MDT) provides precise tracking and momentum measurement in the ATLAS muon spectrometer. To accommodate higher event rates and provide better fake rejection in the High Luminosity LHC, a new integrated chamber with small-diameter MDT (sMDT) and thin Resistive Plate Chambers (tRPC) had been developed and will be installed into barrel inner layer of the muon detector for the phase-2 upgrade. The BIS78 project serves as a pilot project for the barrel inner layer upgrade (1 < |η| < 1.3) during the LHC LS1 shutdown (2019-2021). Several sMDT+tRPC chambers have been installed and operated in the ATLAS detector. An overview of the commissioning status of BIS78 in the ATLAS experiment will be presented.
Speaker: Meng-Ju Tsai (University of Michigan) -
45
Improvements to and Functionality Testing of ATLAS Online Trigger Rate Prediction Tool in Preparation for Run 3
The ATLAS detector at the LHC is subject to millions of events per second. ATLAS employs a trigger system to select events of high importance for offline storage. To ensure the triggers are working as expected, we use a software tool called xMon, which has been in operation in the ATLAS control room for a decade. xMon works by predicting the trigger rate based on offline fits from previous runs, which can then be compared to the live trigger rates at ATLAS. We discuss the recent developments to prepare xMon for Run 3: (1) formatting the new visual interface hosted within the Grafana TRP dashboard, (2) analysis of results from pilot beam data, (3) addition of a bunch factor callback function.
Speaker: Enzo Daniele Brandani (University of Pittsburgh (US)) -
46
Improvements to and Functionality Testing of ATLAS Online Trigger Rate Prediction Tool in Preparation for Run 3
The ATLAS detector at the LHC is subject to millions of events per second. ATLAS employs a trigger system to select events of high-importance for offline storage. To ensure the triggers are working as expected, we use a software tool called xMon, which has been in operation in the ATLAS control room for a decade. xMon works by predicting the trigger rate based on offline fits from previous runs, which can then be compared to the live trigger rates at ATLAS. We discuss the recent developments to prepare xMon for Run 3: (1) formatting the new visual interface hosted within the Grafana TRP dashboard, (2) analysis of results from pilot beam data, (3) addition of a bunch factor callback function.
Speaker: Enzo Daniele Brandani (University of Pittsburgh (US))
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41
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