Student Seminars

[14:30-14:50] Jan H. Kwapisz (University of Warsaw)
Asymptotic safety and Conformal Standard Model

There are many proposals how to extend the Standard Model, designed to deal with its fundamental inconsistencies. Since no new particles have been detected experimentally so far, the models which add only one more scalar particle and possibly right-chiral neutrinos are favoured. One of them is the Conformal Standard Model, which proposes a coherent solution to the Standard Model drawbacks including the hierarchy problem and a dark matter candidate. On the other hand there are signs that gravity is asymptotically safe. If there are no intermediate scales between electroweak and Planck scale then the Conformal Standard Model supplemented with asymptotically safe gravity can be valid up to arbitrarily high energies and give a complete description of particle physics phenomena. Moreover asymptotic safety hypothesis restricts the mass of the second scalar particle to 300 +/-28 GeV for negative anomalous dimension of lambda 3, while for positive second scalar particle is decoupled. The masses of heavy neutrinos can also be estimated as 342 +/- 41 GeV. These predictions can be explicitly tested in the nearby future. 

[14:50-15:10] Shu-Yu Ho (Tohoku University, Japan)
Relaxing the Cosmological Moduli Problem by Low-scale Inflation

We show that the cosmological abundance of string axions is much smaller than naive estimates if the Hubble scale of inflation, Hinf, is sufficiently low (but can still be much higher than the axion masses) and if the inflation lasts sufficiently long. The reason is that the initial misalignment angles of the string axions follow the Bunch-Davies distribution peaked at the potential minima. As a result, the cosmological moduli problem induced by the string axions can be significantly relaxed by low-scale inflation, and astrophysical and cosmological bounds are satisfied over a wide range of the mass without any fine-tuning of the initial misalignment angles. Specifically, the axion with its decay constant f_φ = 10^16 GeV satisfies the bounds over 10^−18 eV < m_φ < 10 TeV for Hinf < 10 keV ~ 10^6 GeV. We also briefly discuss cases with multiple axions and the QCD axion. 

[15:10-15:30] John Tamanas (UC Santa Cruz)
What your GGI Coffee Mug says about You

We study the distribution of coffee mugs administered during the 2019 Galileo Galilei Institute School on the Theory of Fundamental Interactions (GGI). Using unsupervised and supervised machine learning methods, we determine the parameters that contributed to the choice of mug for every individual. With the introduction of a novel embedding of national data, we are able to use robust regression techniques to train our models.

[16:00-16:20] Carissa Cesarotti (Harvard University)
Searching for New Physics in CMS Open Data

We study dimuon events in 2.11 fb-1 of 7 TeV pp collisions, using CMS Open Data, and search for a narrow dimuon resonance with moderate mass (14 - 66 GeV) and substantial transverse momentum (pT ). Applying dimuon pT cuts of 25 GeV and 60 GeV, we explore two overlapping samples: one with isolated muons, and one with prompt muons without an isolation requirement. Using the latter sample requires information about detector effects and QCD backgrounds, which we obtain directly from the CMS Open Data. We present model-independent limits on the product of cross section, branching fraction, acceptance, and efficiencies. These limits are stronger, relative to a corresponding inclusive search without a pT cut, by factors of as much as nine. Our "pT -enhanced" dimuon search strategy provides improved sensitivity to models in which a new particle is produced mainly in the decay of something heavier, as could occur, for example, in decays of the Higgs boson or of a TeV-scale top partner. If ATLAS and CMS were to implement this method on current 13 TeV data, sensitivity to such signals should improve by a further order of magnitude. 

[16:20-16:40] Bianka Meçaj (Mainz ITP)
Glauber Gluons

Glauber Gluons are gluons characterised by a large transverse momentum compared to the components along the direction of the colliding hadrons. It is because of this scaling that they are very subtle in violating the factorisation theorem for certain observables. Depending on how and by which hadron they were radiated these effects can be either absorbed using SCET methods or not. This is a very new field of research and not much is known on how the mechanism behind this violation really works. In my presentation I will give a comprehensive introduction of the problem and possible ways to tackle it.