scholarly journals Resonant third-generation leptoquark signatures at the Large Hadron Collider

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Ulrich Haisch ◽  
Giacomo Polesello
Keyword(s):  
Large Hadron Collider ◽  
Top Quark ◽  
Transverse Energy ◽  
Hadron Collider ◽  
Third Generation ◽  
Missing Transverse Energy ◽  
Final State ◽  
Analysis Strategies ◽  
The Masses ◽  
Lepton Flavour

Abstract Given the hints of lepton-flavour non-universality in B-meson decays, leptoquarks (LQs) are enjoying a renaissance. We propose novel Large Hadron Collider (LHC) searches for such hypothetical states that do not rely on strong production only, but can also receive important contributions from quark-lepton annihilation. For the cases of a resonant signal involving a bottom quark and a tau lepton (b + τ), a top quark and missing transverse energy ($$ {E}_T^{\mathrm{miss}} $$ E T miss ) and light-flavour jets plus $$ {E}_T^{\mathrm{miss}} $$ E T miss , we develop realistic analysis strategies and provide detailed evaluations of the achievable sensitivities for the corresponding LQ signatures at future LHC runs. Our analyses allow us to derive a series of stringent constraints on the masses and couplings of third-generation singlet vector LQs, showing that at LHC Run III and the high-luminosity LHC the proposed search channels can probe interesting parts of the LQ parameter space addressing the B-physics anomalies. In view of the reach of the proposed b + τ signature, we recommend that dedicated resonance searches for this final state should be added to the exotics search canon of both ATLAS and CMS.

scholarly journals Search for pair production of third-generation scalar leptoquarks decaying into a top quark and a τ-lepton in pp collisions at $$ \sqrt{s} $$ = 13 TeV with the ATLAS detector

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
◽  
G. Aad ◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
...  
Keyword(s):  
Pair Production ◽  
Top Quark ◽  
Production Cross ◽  
Branching Fraction ◽  
Hadron Collider ◽  
Atlas Detector ◽  
Third Generation ◽  
Final State ◽  
Generation Scalar ◽  
Scalar Leptoquarks

Abstract A search for pair production of third-generation scalar leptoquarks decaying into a top quark and a τ-lepton is presented. The search is based on a dataset of pp collisions at $$ \sqrt{s} $$ s = 13 TeV recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb−1. Events are selected if they have one light lepton (electron or muon) and at least one hadronically decaying τ -lepton, or at least two light leptons. In addition, two or more jets, at least one of which must be identified as containing b-hadrons, are required. Six final states, defined by the multiplicity and flavour of lepton candidates, are considered in the analysis. Each of them is split into multiple event categories to simultaneously search for the signal and constrain several leading backgrounds. The signal-rich event categories require at least one hadronically decaying τ-lepton candidate and exploit the presence of energetic final-state objects, which is characteristic of signal events. No significant excess above the Standard Model expectation is observed in any of the considered event categories, and 95% CL upper limits are set on the production cross section as a function of the leptoquark mass, for different assumptions about the branching fractions into tτ and bν. Scalar leptoquarks decaying exclusively into tτ are excluded up to masses of 1.43 TeV while, for a branching fraction of 50% into tτ, the lower mass limit is 1.22 TeV.

scholarly journals KK Higgs produced in association with a top quark pair in the bulk RS model

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
N. Manglani ◽  
A. Misra ◽  
K. Sridhar
Keyword(s):  
Higgs Boson ◽  
Large Hadron Collider ◽  
Cross Section ◽  
Top Quark ◽  
Production Cross Section ◽  
Search Strategy ◽  
Production Cross ◽  
Hadron Collider ◽  
Final State ◽  
Kaluza Klein

AbstractWe present a search strategy for the first Kaluza–Klein (KK) mode of the Higgs boson in the framework of the Randall–Sundrum (RS) model with a deformed metric. We study the production of this massive excitation in association with a $$ t {\bar{t}}$$tt¯ pair at the large hadron collider (LHC). The KK Higgs primarily decays into a boosted $$t {\bar{t}}$$tt¯ final state and we then end up with an interesting four-top final state of which two are boosted. The boosted products in the final state improve the sensitivity for the search of the KK Higgs in this channel whose production cross-section is otherwise rather small. Our results suggest that masses of the KK Higgs resonance upto about 1.2 TeV may be explorable at the highest planned luminosities of the LHC. Beyond this mass, the KK Higgs cross-section is too tiny for it to be explored at the LHC and may be possible only at a future higher energy collider.

scholarly journals Search for supersymmetry in events with a single lepton, jets and missing transverse energy with the CMS detector at LHC

2014 ◽  
Author(s):  
Λουκάς Γούσκος
Keyword(s):  
Large Hadron Collider ◽  
Compact Muon Solenoid ◽  
Transverse Energy ◽  
Branching Fraction ◽  
Hadron Collider ◽  
Missing Transverse Energy ◽  
Top Squark ◽  
Lepton Jets ◽  
8 Tev ◽  
Integrated Luminosity

Το αντικείμενο της διατριβής είναι η αναζήτηση υπερσυμμετρικών σωματιδίων σε συγκρούσεις πρωτονίων σε συνολική ενέργεια σύγκρουσης 7 και 8 TeV. Τα δεδομένα συλλέχθηκαν με το πείραμα Compact Muon Solenoid (CMS) κατά τη πρώτη περίοδο λειτουργίας (2010-2012) του επιταχυντή Large Hadron Collider (LHC), αντιστοιχούν σε ολοκληρωμένη φωτεινότητα (integrated luminosity) 4.98 fb-1 και 19.3 fb-1, αντίστοιχα. Η μελέτη εστιάζεται στα κανάλια διάσπασης των υπερσυμμετρικών σωματιδίων που οδηγούν στην παραγωγή γεγονότων με ένα απομονωμένο, ενεργητικό, φορτισμένο λεπτόνιο. Η συγκεκριμένη υπογραφή προσφέρει ένα αξιόπιστο κανάλι παρατήρησης στο αδρονικό περιβάλλον του LHC, διατηρώντας παράλληλα υψηλό κλάσμα διακλάδωσης (branching fraction). Η πρώτη ανάλυση, που αφορά δεδομένα από συγκρούσεις στα 7 TeV, εστιάζεται στην αναζήτηση της υπερσυμμετρίας σε γενικές (inclusive) διαδικασίες. Η δεύτερη ανάλυση, βασισμένη στα δεδομένα των 8 TeV, σχεδιάστηκε για την ανίχνευση υπερσυμμετρικών top squark από την παραγωγή gluinos, , και την ακόλουθη διάσπασή τους μέσω της διαδικασίας . Τα δεδομένα που συλλέχθηκαν στα 7 και 8 TeV αντιστοιχούν σε ολοκληρωμένη φωτεινότητα (integrated luminosity) 4.98 fb-1 και 19.3 fb-1, αντιστοίχα. Και οι δύο αναλύσεις δείχνουν πλήρη συμφωνία των δεδομένων, τόσο των παρατηρούμενων αριθμών γεγονότων όσο και των χαρακτηριστικών τους, με τις προβλέψεις του Καθιερωμένου Προτύπου σε όλες στις περιοχές αναζήτησης. Τα αποτελέσματα χρησιμοποιούνται για τον υπολογισμό κατωτάτων ορίων στις μάζες των υπερσυμμετρικών σωματιδίων. Τέλος, γίνεται μελέτη της παρατηρησιμότητας της διαδικασίας σε μελλοντικές συγκρούσεις πρωτονίων στον LHC σε ολική ενέργεια 14 TeV, δινοντας έμφαση στην επίδραση των διαφορετικών συνθηκών λήψης και των διαφορετικών αναβαθμίσεων του CMS, στην αποδοτικότητα της ανακατασκευής των φυσικών αντικειμένων και στην ευαισθησία (sensitivity) της έρευνας.

scholarly journals Phenomenology of vector-like leptons with Deep Learning at the Large Hadron Collider

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Felipe F. Freitas ◽  
João Gonçalves ◽  
António P. Morais ◽  
Roman Pasechnik
Keyword(s):  
Deep Learning ◽  
Large Hadron Collider ◽  
Transverse Energy ◽  
Vector Boson ◽  
Hadron Collider ◽  
Grand Unification ◽  
Detector Response ◽  
Sterile Neutrinos ◽  
Final State ◽  
200 Gev

Abstract In this paper, a model inspired by Grand Unification principles featuring three generations of vector-like fermions, new Higgs doublets and a rich neutrino sector at the low scale is presented. Using the state-of-the-art Deep Learning techniques we perform the first phenomenological analysis of this model focusing on the study of new charged vector-like leptons (VLLs) and their possible signatures at CERN’s Large Hadron Collider (LHC). In our numerical analysis we consider signal events for vector-boson fusion and VLL pair production topologies, both involving a final state containing a pair of charged leptons of different flavor and two sterile neutrinos that provide a missing energy. We also consider the case of VLL single production where, in addition to a pair of sterile neutrinos, the final state contains only one charged lepton. We propose a novel method to identify missing transverse energy vectors by comparing the detector response with Monte-Carlo simulated data. All calculated observables are provided as data sets for Deep Learning analysis, where a neural network is constructed, based on results obtained via an evolutive algorithm, whose objective is to maximise either the accuracy metric or the Asimov significance for different masses of the VLL. Taking into account the effect of the three analysed topologies, we have found that the combined significance for the observation of new VLLs at the high-luminosity LHC can range from 5.7σ, for a mass of 1.25 TeV, all the way up to 28σ if the VLL mass is 200 GeV. We have also shown that by the end of the LHC Run-III a 200 GeV VLL can be excluded with a confidence of 8.8 standard deviations. The results obtained show that our model can be probed well before the end of the LHC operations and, in particular, providing important phenomenological information to constrain the energy scale at which new gauge symmetries emergent from the considered Grand Unification picture can be manifest.

scholarly journals Searching for the Minimal Seesaw Models at the LHC and Beyond

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Arindam Das
Keyword(s):  
Transverse Energy ◽  
Hadron Collider ◽  
High Energy ◽  
Lepton Number ◽  
Type I ◽  
Missing Transverse Energy ◽  
Final State ◽  
Proton Proton ◽  
Mixing Parameters ◽  
Flavor Mixing

The existence of the tiny neutrino mass and the flavor mixing can be naturally explained by type I Seesaw model which is probably the simplest extension of the Standard Model (SM) using Majorana type SM gauge singlet heavy Right Handed Neutrinos (RHNs). If the RHNs are around the Electroweak- (EW-) scale having sizable mixings with the SM light neutrinos, they can be produced at the high energy colliders such as Large Hadron Collider (LHC) and future 100 TeV proton-proton (pp) collider through the characteristic signatures with the same-sign dilepton introducing lepton number violations (LNV). On the other hand Seesaw models, namely, inverse Seesaw, with small LNV parameter can accommodate EW-scale pseudo-Dirac neutrinos with sizable mixings with SM light neutrinos while satisfying the neutrino oscillation data. Due to the smallness of the LNV parameter of such models, the “smoking-gun” signature of same-sign dilepton is suppressed where the RHNs in the model will be manifested at the LHC and future 100 TeV pp collider dominantly through the Lepton number conserving (LNC) trilepton final state with Missing Transverse Energy (MET). Studying various production channels of such RHNs, we give an updated upper bound on the mixing parameters of the light-heavy neutrinos at the 13 TeV LHC and future 100 TeV pp collider.

scholarly journals The CMS Particle Flow Algorithm

2018 ◽  
Vol 191 ◽  
pp. 02016
Author(s):  
Milos Dordevic
Keyword(s):  
Transverse Energy ◽  
Hadron Collider ◽  
Particle Flow ◽  
Tau Leptons ◽  
Missing Transverse Energy ◽  
Final State ◽  
Event Reconstruction ◽  
Flow Algorithm ◽  
And Performance ◽  
Traditional Approaches

The event reconstruction at the Compact Muon Solenoid (CMS) experiment at the CERN Large Hadron Collider (LHC) is predominantly based on the Particle Flow algorithm. This algorithm for a global event description uses the information from all subdetector systems, unlike the previous, traditional approaches that were focused on the localized information in each subdetector. These traditional methods use the raw information (tracks, hits), while the Particle Flow algorithm completely reconstructs the event by identifying and reconstructing the comprehensive list of final-state particles (photons, electrons, muons, charged and neutral hadrons), resulting in superior reconstruction of jets, missing transverse energy, tau leptons, electrons and muons. This approach also allows for efficient identification and mitigation of the pileup effect. The concept and performance of the Particle Flow algorithm, together with the prospects for its development in the context of the upgraded CMS detector, are presented in this overview.

Implementation of the CMS-SUS-19-006 analysis in the MadAnalysis 5 framework (supersymmetry with large hadronic activity and missing transverse energy; 137 fb−1)

2020 ◽  
pp. 2141007
Author(s):  
Malte Mrowietz ◽  
Sam Bein ◽  
Jory Sonneveld
Keyword(s):  
Transverse Momentum ◽  
Transverse Energy ◽  
Final States ◽  
Missing Transverse Energy ◽  
Final State ◽  
Data Set ◽  
Proton Proton ◽  
Missing Transverse Momentum ◽  
Proton Data ◽  
Two Jets

We present the MadAnalysis 5 implementation and validation of the analysis Search for supersymmetry in proton-proton collisions at 13 TeV in final states with jets and missing transverse momentum (CMS-SUS-19-006). The search targets signatures with at least two jets and large missing transverse momentum in the all-hadronic final state. The analyzed luminosity is 137 fb[Formula: see text], corresponding to the Run 2 proton-proton data set recorded by the CMS detector at 13 TeV. This implementation has been validated in a variety of simplified models, by comparing derived cut flow tables and histograms with information provided by the CMS collaboration, using event samples that we simulated for the purpose of this re-implementation study. The validation is found to reproduce the signal acceptance in most cases.

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