Automatised Constraints on New Physics at the LHC and Beyond

256 Pages·2016·11.35 MB·English

by  Daniel Schmeier

Automatised Constraints on New Physics at
the LHC and Beyond
Dissertation
zur
Erlangung des Doktorgrades (Dr. rer. nat.)
der
Mathematisch-Naturwissenschaftlichen Fakult¨at
der
Rheinischen Friedrich-Wilhelms-Universit¨at Bonn
von
Daniel Schmeier
aus
Ko¨ln
Bonn, 06.06.2016
Dieser Forschungsbericht wurde als Dissertation von der
Mathematisch-Naturwissenschaftlichen Fakult¨at der Universit¨at Bonn angenommen und ist
auf dem Hochschulschriftenserver der ULB Bonn
http://hss.ulb.uni-bonn.de/diss_online elektronisch publiziert.
1. Gutachter: Prof. Herbert K. Dreiner, Ph.D.
2. Gutachter: Prof. Dr. Manuel Drees
Tag der Promotion: 25.08.2016
Erscheinungsjahr: 2016
Summary
In this thesis, we discuss the development and use cases of the public software CheckMATE
which is designed to allow for easy tests of theories beyond the Standard Model against current
results from the Large Hadron Collider (LHC). We illustrate the general functionality of this
tool and provide hands-on examples to explain how it can be used to test results from the
ATLAS and CMS experiments. In addition, we explain how new analyses can be conveniently
added to the existing framework. This tool is then used to project a search for monojet final
states to a high luminosity LHC with a centre-of-mass energy of 14TeV. Here, our prospective
analysis is used to determine the expected sensitivity to a Higgs Portal scenario which couples
the Standard Model to a hidden sector via an invisibly decaying second heavy scalar. We show
that complementary bounds to those derived from Higgs boson searches in 8TeV LHC data
can be set, however only if a significant reduction of the current systematic uncertainties for
the background estimates of such a search can be achieved. Furthermore, we use CheckMATE
and its large set of implemented searches for natural Supersymmetry to show how an extension
of the Minimal Supersymmetric Standard Model by an additional chiral gauge singlet typically
reducestheLHCsensitivity. InthecontextofR-parityviolatingSupersymmetry, wegobeyond
CheckMATE and the LHC and derive how the expected sensitivity of the proposed fixed-target
experiment SHiP to observe long-lived neutralinos produced via rare Standard Model meson
decays can significantly improve existing bounds from low energy observations.

Acknowledgements
There are a lot of people which supported me in various aspects within the last few years and
to whom I owe at least some words of gratitude at this stage.
First and foremost I am very thankful to Herbi for taking me as his PhD student and for
having given me such an exceptionally large amount of freedom in choosing my own research
path. I also feel honoured of having deserved staying in his group until the very end, despite
my unusual place of residence and my severe lack of interest in sports of any kind.
My thanks also go to the remaining assessors of this dissertation, to Manuel Drees for his
interesting and instructive contributions to our discussions during lunch breaks, Journal Clubs
and the like, to Philip Bechtle for exhaustively testing the performance of CheckMATE in the
high statistics limit and to Martin Langer for spending the time and effort of refereeing this
thesis.
I can hardly express the amount of respect and thankfulness I owe to Jamie who always
supported me from the beginning of my first Master’s project until the final revision of this
document and who encouraged me to take the risk and work on CheckMATE — the most suc-
cessful project of my scientific carreer so far.
I am extremely lucky to have experienced the luxury of wonderful colleagues in the last few
years. For the great athmosphere which has always made me enjoy coming to the BCTP I want
to thank my original ‘PhD-Rangers’ Kilian, Tim, Toby and Stefano, our youngest ‘Desperate
Gradstudent’ Annika, my new prot´eg´e Sebastian, ‘the elder’ Florian, Lorenzo, Martin and
Manuel as well as ‘the supporters’ Dagmar, Petra, Patricia, Christa and Leni. I also want to
thank my long-term remote colleague Jong Soo for all the fruitful collaborations until now and
my former competitor Sabine for her hospitality in Grenoble where a sizable fraction of this
work was written. The old and new co-CheckMATE-ers also deserve my appreciation for their
contribution to the tool’s success.
ForthegreatamountofactiveandpassivesupportoutsideofAcademiaIwanttothankboth
my family and my future family in-law. The ladies of our annual Thursday night meetings,
in particular Sonja, also deserve my words of thanks for the wonderful dishes they served, the
gossip they provided me with and for the countless hours of fun I had.
I want to close with a big thank you to you, Elena. I am grateful for all your love, support
and understanding in the past years. You are the most important person in my life and each
day I am happy to have you around. I love you.

List of Publications
The projects presented within this thesis contain results published in the following journals and
preprint archives:
Jordy de Vries, Herbert Dreiner, Daniel Schmeier
“R-Parity Violation and Light Neutralinos at SHiP and the LHC”
arXiv:1511.07436 [hep-ph] (Submitted to Phys.Rev)
Jong Soo Kim, Daniel Schmeier, Jamie Tattersall
“Naughty or Nice? The Role of the ‘N’ in the Natural NMSSM for the LHC”
arXiv:1510.04871 [hep-ph], Phys.Rev. D93 (2016) No.5, 055018
Jong Soo Kim, Oleg Lebedev, Daniel Schmeier
“Higgsophilic gauge bosons and monojets at the LHC”
arXiv:1507.08673 [hep-ph], J.High Energ.Phys. 11 (2015) 128
Sergey Alekhin et al.
“A facility to Search for Hidden Particles at the CERN SPS: the SHiP physics case”
arXiv:1504.04855 [hep-ph] (Accepted in Rep.Prog.Phys.)
Jong Soo Kim, Daniel Schmeier, Jamie Tattersall, Krzysztof Rolbiecki
“A framework to create customised LHC analyses within CheckMATE”
arXiv:1503.01123 [hep-ph], Comput.Phys.Commun. 196 (2015) 535-562
Manuel Drees, Herbert Dreiner, Jong Soo Kim, Daniel Schmeier, Jamie Tattersall
“CheckMATE: Confronting your Favourite New Physics Model with LHC Data”
arXiv:1312.2591 [hep-ph], Comput.Phys.Commun. 187 (2014) 227-265

Contents
1 Introduction 1
2 Theories of Nature — The Standard Model and Beyond 5
2.1 Introduction to the Standard Model . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Higgs Portal Extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3 Introduction to General Supersymmetric Models . . . . . . . . . . . . . . . . . . 19
2.4 Minimal Supersymmetric Standard Model . . . . . . . . . . . . . . . . . . . . . . 22
2.5 A Natural Next-To-Minimal Supersymmetric Standard Model . . . . . . . . . . . 30
2.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3 Principles of Monte-Carlo Based Proton-Proton Collider Phenomenology 39
3.1 Model Building and Interpretation . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.2 Production Cross Section σ and Monte-Carlo Event Generation . . . . . . . 42
pp→X
3.3 Acceptance (X) and Final State Efficiency (cid:15)(X) . . . . . . . . . . . . . . . . . 52
A
3.4 Choosing X . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
3.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
4 Automatised LHC Tests with CheckMATE 63
4.1 General Program Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.2 Example: Running CheckMATE and Understanding the Results. . . . . . . . . . . 69
4.3 Detector Tunings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
4.4 Details on the CheckMATE Analysis Framework . . . . . . . . . . . . . . . . . . . 91
4.5 Example: Adding a New Analysis to CheckMATE . . . . . . . . . . . . . . . . . . 100
4.6 Summary and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
5 Probing the Higgs Portal at the LHC via Monojets 113
5.1 Theoretical Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
5.2 Experimental Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
5.3 Available Parameter Space and Invisible Branching Ratios . . . . . . . . . . . . . 118
5.4 Future Limits from LHC Monojet Searches . . . . . . . . . . . . . . . . . . . . . 120
5.5 Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
5.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
6 Natural NMSSM Decay Chains at the LHC 129
6.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
6.2 Spectrum and Decays in the Natural NMSSM . . . . . . . . . . . . . . . . . . . . 132
6.3 Model Test Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
6.4 Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
6.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
7 R-Parity Violation and Light Neutralinos at SHiP and the LHC 149
7.1 Experimental Situation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
7.2 Light Neutralinos at SHiP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
7.3 Effective Lepton-Neutralino-Meson Interactions . . . . . . . . . . . . . . . . . . . 155
7.4 Observable Signatures of R-Parity Violation . . . . . . . . . . . . . . . . . . . . . 160
7.5 Simulation of RPV Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
7.6 Results for Various Benchmark Scenarios . . . . . . . . . . . . . . . . . . . . . . 165
7.7 LHC Estimate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
7.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
8 Conclusions and Outlook 181
A Additional Information for Chapter 3 187
A.1 Integrated Luminosity L . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
A.2 Statistical Evaluation Revised . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
B Additional Information for Chapter 4 191
B.1 Installing CheckMATE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
B.2 Full List of CheckMATE Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . 193
B.3 CheckMATE Detector Tunings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
C Additional Information for Chapter 6 209
C.1 Distributions for the Natural NMSSM Scan . . . . . . . . . . . . . . . . . . . . . 209
Bibliography 219