https://digital.csic.es/bitstream/10261/108964/1/experiment%20at%20the%20LHC.pdf

Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC

We describe likelihood-based statistical tests for use in high energy physics for the discovery of new phenomena and for construction of confidence intervals on model parameters. We focus on the properties of the test procedures that allow one to account for systematic uncertainties. Explicit formulae for the asymptotic distributions of test statistics are derived using results of Wilks and Wald. We motivate and justify the use of a representative data set, called the “Asimov data set”, which provides a simple method to obtain the median experimental sensitivity of a search or measurement as well as fluctuations about this expectation.

/pdf/asymptotic-formulae-for-likelihood-based-tests-of-new-3k1xp8edqf.pdf

Asymptotic formulae for likelihood-based tests of new physics

Search for the standard model Higgs boson at LEP

CMS is a general purpose experiment, designed to study the physics of pp collisions at 14 TeV at the Large Hadron Collider (LHC). It currently involves more than 2000 physicists from more than 150 institutes and 37 countries. The LHC will provide extraordinary opportunities for particle physics based on its unprecedented collision energy and luminosity when it begins operation in 2007. The principal aim of this report is to present the strategy of CMS to explore the rich physics programme offered by the LHC. This volume demonstrates the physics capability of the CMS experiment. The prime goals of CMS are to explore physics at the TeV scale and to study the mechanism of electroweak symmetry breaking--through the discovery of the Higgs particle or otherwise. To carry out this task, CMS must be prepared to search for new particles, such as the Higgs boson or supersymmetric partners of the Standard Model particles, from the start-up of the LHC since new physics at the TeV scale may manifest itself with modest data samples of the order of a few fb−1 or less. The analysis tools that have been developed are applied to study in great detail and with all the methodology of performing an analysis on CMS data specific benchmark processes upon which to gauge the performance of CMS. These processes cover several Higgs boson decay channels, the production and decay of new particles such as Z' and supersymmetric particles, Bs production and processes in heavy ion collisions. The simulation of these benchmark processes includes subtle effects such as possible detector miscalibration and misalignment. Besides these benchmark processes, the physics reach of CMS is studied for a large number of signatures arising in the Standard Model and also in theories beyond the Standard Model for integrated luminosities ranging from 1 fb−1 to 30 fb−1. The Standard Model processes include QCD, B-physics, diffraction, detailed studies of the top quark properties, and electroweak physics topics such as the W and Z0 boson properties. The production and decay of the Higgs particle is studied for many observable decays, and the precision with which the Higgs boson properties can be derived is determined. About ten different supersymmetry benchmark points are analysed using full simulation. The CMS discovery reach is evaluated in the SUSY parameter space covering a large variety of decay signatures. Furthermore, the discovery reach for a plethora of alternative models for new physics is explored, notably extra dimensions, new vector boson high mass states, little Higgs models, technicolour and others. Methods to discriminate between models have been investigated. This report is organized as follows. Chapter 1, the Introduction, describes the context of this document. Chapters 2-6 describe examples of full analyses, with photons, electrons, muons, jets, missing ET, B-mesons and τ's, and for quarkonia in heavy ion collisions. Chapters 7-15 describe the physics reach for Standard Model processes, Higgs discovery and searches for new physics beyond the Standard Model

CMS physics technical design report, volume II: Physics performance

http://digital.csic.es/bitstream/10261/46123/1/0811.4169v4.pdf

HiggsBounds: Confronting arbitrary Higgs sectors with exclusion bounds from LEP and the Tevatron

This article describes an efficient procedure for computing approximate confidence levels for searches for new particles where the expected signal and background levels are small enough to require the use of Poisson statistics. The results of many independent searches for the same particle may be combined easily, regardless of the discriminating variables which may be measured for the candidate events. The effects of systematic uncertainty in the signal and background models are incorporated in the confidence levels. The procedure described allows efficient computation of expected confidence levels.

/pdf/confidence-level-computation-for-combining-searches-with-2rpyi0wu9m.pdf

Confidence level computation for combining searches with small statistics

Confidence Level Computation for Combining Searches with Small Statistics

We review the techniques and results of the searches for the Higgs boson performed by the two Tevatron collaborations, CDF and DO. The Higgs boson predicted by the Standard Model was sought in the mass range 90 GeV < mH < 200 GeV in all main production modes at the Tevatron: gluon–gluon fusion, WH and ZH associated production, vector boson fusion, and production, and in five main decay modes: , H→τ+τ-, H→WW(*), H→ZZ(*) and H→γγ. An excess of events was seen in the searches consistent with a Standard Model Higgs boson with a mass in the range 115 GeV < mH < 135 GeV. Assuming a Higgs boson mass of mH = 125 GeV, studies of Higgs boson properties were performed, including measurements of the product of the cross section times the branching ratio in various production and decay modes, constraints on Higgs boson couplings to fermions and vector bosons, and tests of spin and parity. We also summarize the results of searches for supersymmetric Higgs bosons, and Higgs bosons in other extensions of the Standard Model.

https://lss.fnal.gov/archive/2014/pub/fermilab-pub-14-349-e.pdf

Review of Physics Results from the Tevatron: Higgs Boson Physics

We review the techniques and results of the searches for the Higgs boson performed by the two Tevatron collaborations, CDF and DO. The Higgs boson predicted by the Standard Model was sought in the mass range 90 GeV$<m_H<200$ GeV in all main production modes at the Tevatron: gluon-gluon fusion, $WH$ and $ZH$ associated production, vector boson fusion, and $t\bar{t}H$ production, and in five main decay modes: $H\rightarrow b{\bar{b}}$, $H\rightarrow \tau^+\tau^-$, $H\rightarrow WW^{(*)}$, $H\rightarrow ZZ^{(*)}$, and $H\rightarrow\gamma\gamma$. An excess of events was seen in the $H\rightarrow b{\bar{b}}$ searches consistent with a Standard Model Higgs boson with a mass in the range 115 GeV$<m_H<$135 GeV. Assuming a Higgs boson mass of $m_H=125$ GeV, studies of Higgs boson properties were performed, including measurements of the product of the cross section times branching the ratio in various production and decay modes, constraints on Higgs boson couplings to fermions and vector bosons, and tests of spin and parity. We also summarize the results of searches for supersymmetric Higgs bosons, and Higgs bosons in other extensions of the Standard Model.

Thomas R. Junk

Papers

Confidence level computation for combining searches with small statistics

Confidence Level Computation for Combining Searches with Small Statistics

Review of Physics Results from the Tevatron: Higgs Boson Physics

Review of Physics Results from the Tevatron: Higgs Boson Physics