Search for multiple Higgs boson production in hadronic final states at the Large Hadron Collider

doctoral thesis

• Title (croatian): Potraga za višestrukom produkcijom Higgsovih bozona u hadronskim konačnim stanjima na Velikom hadronskom sudarivaču
• Author: Bhakti Kanulal Chitroda
• Mentor: Dinko Ferenček (mentor)
• Committee member: Vuko Brigljević (predsjednik povjerenstva)
• Committee member: Nikola Poljak (član povjerenstva)
• Committee member: Ivica Friščić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2024-12-19, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics
• Universal decimal classification (UDC): 53 - Physics

Abstract

After the discovery of the Higgs boson, one of the main purposes of the physics program at the LHC has been a thorough characterization of its properties. Among important properties of Higgs lies trilinear and quartic Higgs self-coupling, accessible through di- Higgs and triple Higgs production respectively. This thesis primarily reports on two highly significant and intriguing studies that were performed utilizing data from the Run- 2(2016–2018) proton–proton collision at a center-of-mass energy of 13 TeV collected by the CMS experiment at the LHC. The first study concerns the search for the non-resonant H pair produced through gluon-gluon fusion (ggF) and Vector Boson Fusion (VBF) modes in two photons and two b-jets final state. The b￣bγγ final state is one of the most sensitive channels to the HH signal thanks to a relatively clean signature of two high-energy photons and large branching ratio of two heavy-flavor high-energy jets (b-jets). A 95% confidence level (CL) upper limit on the product of Higgs boson pair production cross section and branching fraction are derived as a function of κλ parameter. The constraints on the anomalous coupling of a pair of H with a pair of gauge bosons was determined for the first time by the CMS collaboration. The second study focuses on the search for triple Higgs boson production in three b-jet pairs final state. Given the extremely low standard model (SM) cross-section for triple- Higgs production, the Two-Real Singlet Model (TRSM) is considered as an extension of SM. TRSM introduces two real scalars X and Y, which decay to three SM Higgs bosons which decays further to three pair of b-quarks through the process X → Y H → HHH → b￣bb￣bb￣ b. The search is performed in mass ranges of X (1–4 TeV) and Y (300–2800 GeV) where the H is highly Lorentz-boosted. In this kinematic regime, decayed b-quark pairs are collimated enough to allow the reconstruction of H using single large-area jets. We have considered two topologies: one topology where all three Higgs bosons are boosted and another where two of the three Higgs bosons are boosted. This analysis is still ongoing. A scan will be performed in a two dimensional plane spanned by the invariant mass of the two large-area jets associated to Y, and the invariant mass of three large-area jets used to reconstruct X.

Abstract (english)

Rad ne sadrži sažetak na drugom jeziku.

• Keywords: LHC; CMS; standard model; Higgs boson; Higgs self-coupling; TRSM; boosted objects; b-quarks; photons; Higgs-pair; triple Higgs
• Keywords (english): Rad ne sadrži ključne riječi na drugom jeziku.
• Language: english
• URN:NBN: urn:nbn:hr:217:911256
• Promotion: 2025
• Study programme: Title: Doctoral study; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti u području prirodnih znanosti (doktor/doktorica znanosti u području prirodnih znanosti)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2025-01-21 12:39:31