Title Produkcija tripleta Higgsovih bozona na Velikom hadronskom sudarivaču Title (english) Triple Higgs boson production at the Large Hadron Collider Author Filip Bilandžija Mentor Vuko Brigljević (mentor)Committee member Vuko Brigljević (predsjednik povjerenstva)Committee member Krešimir Kumerički (član povjerenstva)Committee member Sanjin Benić (član povjerenstva)Committee member Davor Horvatić (član povjerenstva)Committee member Petar Žugec (član povjerenstva)Granter University of Zagreb Defense date and country 2023-07-07, Croatia Scientific / art field, NATURAL SCIENCES Abstract U fizici elementarnih čestica, standardni model čestica opisuje svo (ili skoro svo) naše znanje tog područja. Također, standardni model predviđa da procese i njihova svojstva poput udarnih presjeka s iznimnom preciznošću koja je u skladu s mnogim eksperimentima. No, standardni model nije zaokružen kao teorija jer još uvijek postoje dijelovi fizike poput gravitacije ili tamne tvari koji njime nisu obuhvaćeni. Zbog toga postoji mnoštvo modela kojima je cilj proširiti standardni model i na ta
... More područja. Jedno od jednostavnijih mogućih proširenja nalazi se u Higgsovom sektoru. U standardnom je modelu rješenje kojim se postiže Higgsov mehanizam, ključan za dobivanje masa čestica, najjednostavnije moguće. No, ništa ne sprječava postojanje nekog kompleksnijeg rješenja. Jedno takvo kompleksnije rješenje je u obliku dva dodatna skalarna polja u Higgsovom sektoru čime se predviđa postojanje dvije nove skalarne čestice, X i Y. Te čestice, u režimu masa MX > MY + MH i MY > 2MH, mogu se raspasti u 3 Higgsova bozona u kaskadi X → Y H → HHH. Iako u Standardnom modelu postoje mogućnost produkcije 3 Higgsova bozona u sudaru, udarni je presjek na taj proces iznimno malen i iznosi oko 0.1 fb. U ovome radu predstavljamo rezonantnu potragu za tim dvjema česticama u njihovom raspadu na 3 Higgsova bozona u kinematičkom režimu u kojem će producirani Higgsovi bozoni imati dovoljno veliki impuls da parovi b kvarkova iz njihovo raspada budu kolimirani. Prvo je dana analiza koristeći Monte-Carlo simulacije za pozadinu i dane su očekivane vrijednosti gornjih granica udarnog presjeka signalnog procesa. Zbog sistematskog neslaganja podataka sa Monte-Carlo simulacijama, dana je i alternativna, realističnija, analiza gdje je pozadina procijenjena iz podataka. Detaljno je objašnjena metoda procjene pozadine te su dani rezultati metode zajedno s rezultatima statističkih testova. Na kraju su dane i očekivane vrijednosti gornjih granica za udarni presjek signalnog procesa dobivene metodom podatkovne procjene pozadine. Te očekivane gornje granice udarnih presjeka su reda veličine 1 fb u režimima masa u kojima je svaki par b kvarkova kolimiran. U režimima gdje postoji velika mogućnost da jedan od parova b kvarkova nije kolimiran, naša analiza nije dovoljno osjetljiva te se očekivana gornja granica povećava za nekoliko redova veličine. Less Abstract (english) The Standard Model of Particles is describing all (or almost all) of our knowledge in the field of particle physics. Also, it is predicting processes and their properties, such as cross sections, with great precision that is in agreement with the experiment. But the Standard Model is incomplete as a theory because there are still parts of physics that are not covered by it such as gravity or dark matter. One of the simple possible ways to extend the Standard Model is found in its Higgs
... More sector. In the Standard Model, the solution that achieves the Higgs mechanism, crucial for obtaining the masses of particles, is the simplest possible. However, nothing prevents the existence of a more complex solution. One such solution is in the form of two additional scalar fields in the Higgs sector, which predicts the existence of two new scalar particles, X and Y. Those particles, in the mass regime MX > MY + MH and MY > 2MH, can decay into 3 Higgs bosons in X → Y H → HHH cascade. Although in the Standard Model there is a possibility of producing 3 Higgs bosons in a collision, the expected cross-section for that process is extremely small and amounts to about 0.1 fb. In this thesis, we present a resonant search for those two particles in their 3 Higgs boson decay in the kinematic regime in which the produced Higgs bosons are ultrarelativistic and, therefore, each pair of b jets from the decays is collimated. First, an analysis is given using Monte-Carlo simulation for the background and the expected values of the upper limits of the cross-section of the signal process are given. Due to the systematic disagreement of the data with the Monte-Carlo simulations, an alternative analysis is given where the background is estimated from the data. The data-driven background estimation method is explained in detail and the results of the method are given together with the results of statistical tests. In the end, the expected values of the upper limits for the cross-section of the signal process, obtained by the data-driven background estimation method, are given. Those expected upper limits on the cross-sections are of the order of 1 fb in mass regimes where each pair of b jets is collimated. In regimes where there is a high possibility of a b jet pair not being collimated, our analysis is not sensitive enough, and the expected upper limit increases by several orders of magnitude. Less Keywords
model dva realna skalara
Higgsov bozon
debeli mlaz
podatkovna procjena pozadine
2DAbecedna metoda
Keywords (english)
two real singlets model
Higgs boson
fat jet
data-driven background estimation
2DAlphabet method
Language croatian URN:NBN urn:nbn:hr:217:591113 Study programme Title: The University Integrated Undergraduate and Graduate Programme in Physics; Research Physics; specializations in: Research Physics Type of resource Text File origin Born digital Access conditions Open access Terms of use Created on 2024-01-30 11:36:08
