Choose timezone
Your profile timezone:
Collider Cross Talk
Search for periodic new physics signals
by ,
→
Europe/Zurich
4/3-006 - TH Conference Room (CERN)
Description
Abstract
We will discuss the clockwork gravity model from a theoretical perspective and then the recent ATLAS results from the search for periodic signals in the dielectron and diphoton invariant mass spectra using the full Run 2 data. Clockwork models predict narrowly spaced, semi-periodic spectra of heavy resonances. The gravitational version of the clockwork model, whose continuum limit is the 5D linear dilaton model, can address the question of the hierarchy between the weak and Planck scales by bringing the fundamental higher dimensional Planck scale down to accessible energies. At the LHC, the “clockwork gravitons” would be observed via their decay into two light Standard Model particles. However, conventional bump/tail-hunts are largely insensitive to this type of signal, particularly when its cross-section is small. Originated by a proposal made in JHEP 06 (2018) 009, the new ATLAS analysis approaches the problem from a completely new angle, by exploiting the underlying approximate periodicity feature of the two-particle invariant mass spectrum. Clockwork graviton decays with two electrons or two photons final states are an ideal testbed for this search due to the excellent energy resolution of the ATLAS detector. After convolving the mass spectrum of the gravitons’ tower with the ATLAS detector resolution corresponding to these final states, it resembles a wave-packet. This implies that a transformation exploiting the periodical nature of the signal may be helpful. The ATLAS analysis uses novel search techniques based on continuous wavelet transforms to infer the frequency of periodic signals from the invariant mass spectra and neural network classifiers are used to enhance the sensitivity to periodic resonances. Model-independent searches for deviations from the background-only hypothesis are also performed.
Speakers
Matthew McCullough is a theoretical physicist with a particular focus on (undying obsession for) the microphysical origins of the electroweak scale and Higgs boson, with a particular view towards novel experimental consequences of exotic theories. In years past he has also worked on various other topics, including dark matter model building. Matthew completed his PhD at Oxford in 2011, followed by a Simons Postdoctoral Fellowship at MIT, then in 2014 (2015) by a CERN Fellowship (Staff position) in CERN-TH, where he remains.
Noam Tal Hod is an ATLAS experimental physicist since ~2006, working on very-high-$p_T$ searches for new physics (e.g. $Z^{'} \to ll$) as well as searches and measurements at very-low-pT (e.g. $\tau \to 3\mu$). He has also been and still is working extensively on the ATLAS trigger system and the muon system. After completing his PhD in Tel Aviv University In 2013, he moved for two consecutive postdoc positions at NIKHEF and TRIUMF (both with ATLAS). In 2018 he joined the Weizmann Institute of Science in Israel as a faculty member, where he now leads a research team in ATLAS and in the new LUXE experiment at the Eu.XFEL (Hamburg, Germany). His research interest in ATLAS remains driven by searching for new physics either through direct searches (e.g. heavy bosons, LFV, etc.) or through precision measurement (e.g. $R(K^*)$).
