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HiggsTools Journal Club XIV: Toolkit for discoveries @ LHC

Yacine Haddad (U. Durham & CMS)

The recent results from the LHC on the high mass diphoton research have pointed out an excess at 750 GeV in both ATLAS and CMS experiments. In the wake of these results, a question remains on all lips; Is it really a new boson? When can we say that "the observed excess" on our mass distribution is a new particle? How can we quantify the degree of certainty?

In this talk, we will try to address these critical questions taking as an example the 750 GeV excess and the Higgs discovery in the diphoton channel. Therefore, we will review the statistical methods by introducing the concept of the significance and upper limit under the frequentist and Bayesian approaches. A special attention will be then devoted to results interpretation at LHC.


Video of the event:

Thursday, April 07, 2016
HiggsTools Journal Club XIII Discovery of gravitational waves at LIGO

Marek Szczepańczyk (LIGO Scientific Collaboration)

The Laser Interferometer Gravitational-Wave Observatory (LIGO) advanced-
generation detectors started operation in September 2015 with a great dis-
covery of gravitational waves from merging black holes. This detection is the
beginning of new era of gravitational wave astronomy. Along with looking
optically at the sky we will be able to "hear" the Universe. In my pre-
sentation I will talk about gravitational wave detectors, the data analysis
challenge, the discovery and the future of gravitational wave astronomy. I
will also present my area of expertize, the analysis of Core-Collapse Super-
novae (CCSN). CCSN are explosions of massive stars and they are one of the
most interesting sources of gravitational waves.


Video of the event:

Tuesday, March 08, 2016
HiggsTools Journal Club XII: Master Integrals technique for multi-loop computations: the Differential Equations approach

Elisa Mariani (NIKHEF)

During the nineties a technique called "Master Integrals" was developed
to face efficiently the issue of computing multi-loop diagrams. This method
proved itself extremely powerful, making possible some computations that
had been thought not feasible before, due to the huge number of Feynamn
integrals required. The main feature of the technique is the ability to reduce
this number of Feynman integrals to a set as small as possible of independent
integrals, the Master Integrals. In this talk I will briefly review the basis of
the reduction of an initial set of integrals to a set of Masters, and I will
then focus on their explicit calculation through the so-called technique of
Differential Equations for Master Integrals.

Indico event and slides can be found in:

The video of the event:

Tuesday, February 23, 2016
HiggsTools Journal Club XI: Introduction to SecDec

Stephen Jones (MPI Munich)

Abstract: In perturbative QFT including higher order corrections is often important for improving the accuracy of our predictions. One complication to computing these corrections are the (potentially divergent) integrals which arise in loop/virtual corrections. We will begin by briefly motivating the connection between loop corrections and integrals and introduce the concept of regulating divergent integrals. A procedure for evaluating regulated integrals, known as Sector Decomposition, and a tool which implements it, SecDec, will be introduced. The important features of the procedure will be summarised and, time permitting, a typical use case will be demonstrated.


Tuesday, February 09, 2016
HiggsTools Journal Club X: What’s the matter with CP-Violation?

Shruti Patel (DESY Hamburg)

Abstract: Symmetries surround us–but the universe we live in is actualized through the virtue of their breaking. The study of CP violation plays an essential role in understanding the Baryon asymmetry in the universe. However the Standard Model of particle physics falls short of providing an explanation for the observed asymmetry, and so we look at theories beyond the Standard Model for plausible and viable Baryogenesis scenarios. In this talk, I present a brief overview of the ideas and attempts that have been made to account for the overwhelming domination of matter over antimatter in nature, and review the role of BSM physics in electroweak Baryogenesis.


Tuesday, January 19, 2016
HiggsTools Journal Club IX: Why do experimentalists love Multi-jet merging so much?

Davide Napoletano (University of Durham)

Abstract: Multi-jet merging (and more generally matching and merging) techniques, are broadly used by the experimental community as a tool for “inclusion of higher orders”. This has, many times now, led to the question posed above. The general idea of this talk is to review in a very basic way, side-by-side, both the “theoretically sound way of including higher orders” and the multi-jet merging techniques. The objective then is to provide with a common ground for both theorist and experimentalists to understand each other reasons, and have a discussion on that!


Friday, December 18, 2015
HiggsTools Journal Club VIII: Unlocking the Higgs with the Matrix Element Method

Josep Pata (ETH Zurich)

Abstract: The MEM allows the direct evaluation of likelihoods for a collision event to arise from different underlying QFT hypotheses, thus allowing in principle maximal use of detector information. The goal is to discuss how the MEM is used in Run II searches in CMS, how it compares to other multivariate approaches and what possibilities there are for extending this method to NLO.


And if you missed it:

Tuesday, December 01, 2015
HiggsTools Journal Club VII: If Fixed-Order perturbative QCD fails...

Claudio Muselli (University of Milan)

Abstract: Fixed-Order perturbative QCD is nowadays an established technique to make accurate predictions for collider observables. For inclusive cross-sections, NLO calculations can easily be performed by automatic codes. However, for more exclusive observables, such as transverse momentum or jet distributions, only the LO coefficient of the perturbative series is known for many processes, leading to huge theoretical uncertainties. From this problem arises the necessity to explore new roads to improve on the precision of the calculations within the current computational possibilities. I will dicuss the possibility to use resummation techniques to extract useful information about the unknown next orders, focusing on the resummation at high energy, which has been recently applied to the Higgs pT distribution, allowing to estimate the impact of the quark mass effect beyond LO.

Indico page:

Tuesday, November 10, 2015