PH4100 Major Project

Information regarding 4th year projects based on ATLFAST ntuples. See my Log Book 11, page 10, for useful notes for the project kick-off meetings.

Introduction

In this project the student will be studying the feasibility of the Higgs search with the ATLAS detector at the Large Hadron Collider (LHC), in a given Higgs search channel or channels.

The student is advised to read about the LHC, its physics programme, and past and ongoing searches for the Higgs boson. Select some papers from this list of overview papers.

The fractions of signal and background events that will contribute to a particular final state (eg, tt-->bqq blv) should be calculated using this table of Branching Ratios (BR) (from PYTHIA 6.323). It contains useful data on the BRs of Higgs, W and Z bosons, tau leptons, and more.

ATLFAST ntuples

Information on the simulated samples can be found in my Log Book 11, page 23. All of the samples below include simulation of the underlying event. PYTHIA 6.323 was used to generate the events. The cross-sections quoted below are those provided by PYTHIA (except where explicitly stated otherwise). (See page 36 of Log Book 11 for more details.) The fast simulation of the detector response was carried out with ATLFAST 11.0.5, and the ATLFAST ntuples include Run No and Event No information.

More information: the ATLFAST simulation program; content of the ntuples.

Background samples

The following background samples can be found in linappserv1:/scratch0/ptd/ATLAS/EVTutorial/ReGenWithUE/

1 ls -al *ntp* | grep fastsim | grep _tt_ / total 80k events / PYTHIA sigma = 494.5 pb (but use 800 pb ? instead)
20k Jan  6  2007 fastsim_tt_r8050_ntp.root
20k Jan  7  2007 fastsim_tt_r8052_ntp.root
20k Jan  7  2007 fastsim_tt_r8054_ntp.root
20k Jan  7  2007 fastsim_tt_r8056_ntp.root
 1 ls -al *ntp* | grep fastsim | grep _WW_ / total 70k events / PYTHIA sigma = 70.9 pb 
30k Jan  6  2007 fastsim_WW_r8150_ntp.root
20k Jan  7  2007 fastsim_WW_r8152_ntp.root
20k Jan  7  2007 fastsim_WW_r8154_ntp.root
 1 ls -al *ntp* | grep fastsim | grep _ZW_ / total 50k events / PYTHIA sigma = 27.0 pb
30k Jan  7  2007 fastsim_ZW_r8250_ntp.root
20k Jan  8  2007 fastsim_ZW_r8252_ntp.root
 1 ls -al *ntp* | grep fastsim | grep _ZZ_ / total 50k events / PYTHIA sigma = 11.2 pb
30k Jan  5  2007 fastsim_ZZ_r8350_ntp.root
20k Jan  8  2007 fastsim_ZZ_r8352_ntp.root

Signal samples

The following signal samples are available in linappserv1:/scratch2/ptd/ATLAS/MCsamples/2008/ATLFAST, with the exception of one sample generated in 2007 (*), which is available in linappserv1:/scratch0/ptd/ATLAS/EVTutorial/ReGenWithUE/ instead.

The following table gives details of all the signal samples

Process/details	mh	Run	Size	EvGen	σ x BR	FastSim file	Date completed
GF; h-WW; W-all	120	2050	20k	PYTHIA	2.53 pb	fastsim_GFhWW_m120_r2050_ntp.root (*)	Jan 2007
GF; h-WW; W-all	140	2052	20k	PYTHIA	7.07 pb	fastsim_GFhWW_m140_r2052_ntp.root	12/10/08
GF; h-WW; W-all	160	2054	20k	PYTHIA	10.05 pb	fastsim_GFhWW_m160_r2054_ntp.root	12/10/08
GF; h-WW; W-all	180	2056	20k	PYTHIA	8.31 pb	fastsim_GFhWW_m180_r2056_ntp.root	12/10/08
VBF; h-WW; W-all	120	4050	20k	PYTHIA	0.591 pb	fastsim_VBFhWW_m120_r4050_ntp.root	12/10/08
VBF; h-WW; W-all	140	4052	20k	PYTHIA	1.81 pb	fastsim_VBFhWW_m140_r4052_ntp.root	12/10/08
VBF; h-WW; W-all	160	4054	20k	PYTHIA	2.83 pb	fastsim_VBFhWW_m160_r4054_ntp.root	12/10/08
VBF; h-WW; W-all	180	4056	20k	PYTHIA	2.54 pb	fastsim_VBFhWW_m180_r4056_ntp.root	12/10/08

Analysing the data

The simulated data ntuples can be analysed with the help of an object-oriented data analysis package provided by CERN, called ROOT.

The actual data analysis code will be written by the student, in C++. I will provide you with template code to read in an ntuple, book some histograms, apply some event selection cuts, fill in the histograms and print them to file. (Files run_analysis.C, analysis.C and analysis.h)