SIGNAL AND ACCEPTANCE EFFICIENCIES OF MONOJET PLUS MISSING TRANSVERSE ENERGY EVENTS AT THE LHC AT

= 7 TeV USING THE CMS DETECTOR

Anna Marie Benzon, Phy11L/A2

ampbenzon@mapua .edu.ph

Abstract

This study determines the viability of observing supersymmetry (SUSY) at the LHC using the current CMS analysis on monojet with missing transverse energy (MET) final states.

The SUSY signal and acceptance efficiencies are obtained using CMS software (CMSSW) for 1000 generated events whose final state consists of monojet with MET at the LHC in pp collisions having a center-of-mass energy of 7 TeV. These are done on two scenarios: 1) for generic all SUSY processes; and 2) specifically, for bino-dominated lightest supersymmetric particle (LSP) qg 01 process assuming minimal supersymmetric model (MSSM), R-parity conservation, and light mSUGRA benchmark scenario to produce the mass spectrum of SUSY particles. The latter process has a total signal cross section of = 88.8 fb as produced by Pythia. CMS current [3] monojet selection cuts are applied to discriminate backgrounds and to extract the good events. In both cases where the events yield are 0.2% and 0% using the current CMS cutflow at the end of the analysis, we concluded that it is better not to apply a cut anymore on the lepton. Hence, the acceptance efficiencies for all SUSY processes and bino-dominated LSP are 2.7% and 28.6%, respectively. Furthermore, another four new sets of 500 events are produced and compared with the original 1000 events for both scenarios to yield the uncertainty in the data. For both cases, signal and acceptance efficiencies have 2-3% highest and 0% lowest standard deviation from the average efficiencies. These results are important for event selections and reconstructions in probing new Physics at the LHC such as the supersymmetry.

Key Words: Monojet, Missing transverse energy, Supersymmetry, Large Hadron Collider, CMS detector

Introduction

The Standard Model (SM) is a successful proven theory that is tested up to the TeV-scale, which governs the electromagnetic, weak, and strong nuclear interactions. However, many inconsistencies on the theoretical framework of the SM that make us believe SM is not a complete theory. One of the several anomalies is the so called hierarchy problem. The hierarchyproblem aims to solve the large ratio of M /Mwhere electroweak scale

103 GeV

PEW,

1

and the Planck scale

=

2~1018

GeV.This is one of the primemotivations of

Supersymmetry (SUSY) - to construct an extension theory to the SM (although historically this was not the case as several SUSY proposals were originally started with SUSY algebra and

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SUSY field theories but it was later found that it had a strong valid arguments to provide a solution to the hierarchy problem poses by SM).

This paper explores the phenomenological search for SUSY that can be observed at the Large Hadron Collider (LHC). Signals of monojet final state with missing transverse energy as a signature of SUSY are analysed for all SUSY processes and the bino-dominated scenario denoted as qg 01. In our specific SUSY process, it assumes minimal supersymmetric standard model (MSSM) and R-parity conservation, via the process qg 01 [1].

1. The minimal supersymmetric model

If superpartners have the same mass as with their SM particle partners, they could have been detected long time ago but nature seems do not agree to this conjecture. Thus, SUSY cannot be an exact symmetry of nature; otherwise, there exist a spin-1 particle with exactly the mass and charge of an electron! Hence, SUSY partners cannot be degenerate with their usual partners, rather, it is believed that SUSY must be softly broken at the weak scale. Within MSSM framework, the effective Lagrangian [5,7] is =

+ +

+ +

+ (1)

where, = 1+++ . .

2

3

2

1

+ .(2)

2 2

+ .

where M3, M2, M1 are the gluino, wino, and bino mass terms; the second line contains the (scalar)3 couplings, each of au, ad, a e is a complex 3 3 matrix in family space, with dimension of mass, they are in one-to-one correspondence with the Yukawa couplings of the superpotential;

the third line consist of squark and slepton mass terms, each of , , , , is a 3 3 matrix in family space that can have complex entries but they must be hermitian so that the

Lagrangian is real (for simplicity we do not put tilde in the Q in the, etc); and the last linehave the SUSY-breaking contributions to the Higgs potential 2 , 2 , and b are squared mass

terms that can occur in the MSSM. We expect that

M3, M2, M1, au, ad, ae ~ msoft,

(3)

,

,2,2

, b ~2(4)

,,,

where msoft has the mass scale of not much larger than 1000 GeV. As the name suggests, MSSM describes the fewest number of new particles and new interactions that can be observed as shownin Tables (1.1) and (1.2) [5,10].

2Methodology

The full paper should contain a title page containing the following: 1) title-14 pt. centered and bold; 2) name of Student and section-12 pt, centered and bold; 3) keywords-12 pt. and italic format. The lab report should contain Abstract, Introduction, Methodology, Results and Discussion, Conclusions, and References. Length of the full paper must not exceed: 8,000 words, 10 figures, tables and equations, and 10 pages.

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Results and DiscussionFrom the experiment done, ...

1. Tables and Figures

Tables and figures must be of high quality. In the text, figures should be referred to as Fig. 1 or, Fig. 2 (bold) and describe it. Provide titles above tables and captions below figures. Figure should not be crowded with unnecessary details. Photographs must be sharp and clearly seen. If an image is from one of the references (not originally yours), add the sentence: Image taken from [1] (1 is the number of the reference used). If presenting multiple images on a page, use the following format as shown in Fig. 2.

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Fig. 1. The equipment used in the experiment. Image taken from [1].

(a)(b)

(c)(d)

Fig 2. The equipment used in the experiment (L-R): (a) dynamics cart; (b) dynamic track; (c) vernier caliper; and (d) lenses.

2. Units and Equations

Use SI units for all dimensional quantities. Always provide a blank space before and after the unit. In the text, a simple expression, for example 1/(a+b), should be used. In separate equations, all formulas should be typed in a stack format (numerators over denominators). Equations should be centered, aligned right and numbered using Arabic numerals in round brackets. In the text, equations should be referred to as (1) or (2), etc. Leave an interval of one

4line between an equation and text. For example,

K =1mv2(5)

2

where m is the mass and v is velocity of the box.

In the case of table, explanation must be given on top of the table and left aligned as shown. Table must be labeled sequentially starting from 1, 2, 3, Each table must follow and precede a blank line. Every figure or table that appears in the manuscript must be cited in the context.

Table 1. Describe the table in a complete sentence

TrialFS16.5 N55 cm20.2 N24 cm

Conclusions

The results show that...

References

Journal[1] Benzon, AM, Work, Energy, and Power. Physics Journal J., 29(1), 37-44(2006).

Book

[2] Benzon, AM, Physics book. page#, 2nd Ed., Publisher, Place or country (2008).

URL[3] http://www.blogger.com/profile/17912820107546979105

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