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section {font-weight: bold;font-size: x-large;margin-top: 1.3ex;margin-bottom: 0.7ex;text-align: left;}div.standard {margin-bottom: 2ex;}1 IntroductionIn the Standard Model of particle physics quarks and leptons, which are the so-called fermions, are described as fundamental, elementary particles, with their interactions described as mediated by means of the exchange of another set of elementary particles, more precisely the bosons.

In the case of the electromagnetic interaction the force carrying particles are photons, in the weak interaction case they are W and Z bosons, and finally it is the gluons in the case of the strong interaction. Ever since the experimental discovery of the W and Z bosons, uncovering the mechanism by which they and the fermions acquire mass became one of the primary goals for particle physics. The Standard Model dictates that the W and Z bosons acquire their masses through the Brout-Englert-Higgs symmetry breaking mechanism, giving rise to a massive scalar particle, the Standard Model Higgs boson. 2 The LHCConstructed at CERN in a 27 km long tunnel, The Large Hadron Collider aims to probe the TeV energy scale as the worlds largest particle collider. One of the main scientific goals of the LHC was demystifying the electroweak symmetry breaking mechanism by means of searching for in the Standard Model postulated Higgs boson. The collider has been constructed to accelerate and collide protons at centre-of-mass energies of approximately 14 TeV, and to achieve an instantaneous luminosity of more than 1 0 34 c m -2 s -1 . The counter-rotating proton bunches are separated by a mere 25 ns, giving rise to a bunch crossing rate equalling 40 MHz.

The LHC began operating as of 2010 at s =7 TeV . Following this, in 2011 the number of bunches making up the beams was raised to 1380, changing the separation between the bunches to 50 ns, and giving rise to a significant increase in the luminosity. The centre-of-mass energy was then increased to 8 TeV in 2012, and during that time period the luminosity was also further raised, reaching maximum luminosities of near 7 ? 1 0 33 c m -2 s -1 . In 2011 and during the first months of data taking in 2012, the data accumulated by the CMS experiment, corresponding to slightly more than 5 f b -1 per year, was analyzed, which resulted in the first observation of the Higgs boson. An important experimental variable at CMS or the LHC in general is the pseudorapidity, ? , is defined as ? =- ln ( tan ( ? 2 ) ) , where ? is the polar angle measured from the anticlockwise beam direction. Indicated by ? is the azimuthal angle, measured relative to the axis defined by the beam directions. The component of momentum perpendicular to the beam axis is called the transverse momentum, p T .

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There is also the so-called pileup effect. A detected event often contains signals from multiple proton-proton collision and from more that one bunch crossings. Due to the high proton beam intensity, multiple proton-proton collisions can take place for each bunch crossing. The mean number of p-p collisions per bunch crossing was approximately 10 in 2011 and was raised to roughly 20 by 2012. 3 The CMS experimentHaving been designed as a general-purpose detector, CMS can identify and reconstruct photons, muons, electrons, hadronic jets, and the missing of transverse momentum, carried away by weakly interacting particles, very precisely. CMS consists of multiple sub-detectors, each making use of different technologies, calibration and reconstruction methods.

The backbone of CMS is a superconducting solenoid, giving rise to an axial magnetic field of 3.8 Tesla . Both the central tracker and the calorimeters are positioned inside the the bore of the solenoid. The steel flux return yoke outside the solenoid is filled with ionized gas detectors which is used to detect and reconstruct muons.

Trajectories of electrically charged particles are measured by a silicon pixel and strip tracker. This instrument has full coverage within a pseudo-rapidity range of | ? |<2.5 . A hadronic calorimeter, HCAL, and an electromagnetic calorimeter, ECAL, surround this tracking region and azimuthally covers a range inside of | ? |<3 . ECAL's barrel itself is located inside | ? |<1.

5 with additional coverage by the ECAL endcaps within 1.5<| ? |<3.0 . Next to that there is also a pre-shower detector covering the in the area in between 1.65<| ? |<2.6 .

The pre-shower detector is capable of recording the x, y position of incoming particles through two planes of silicon sensors. Finally, the coverage of the calorimeter is enlarged up to | ? |<5.0 by the Cherenkov forward calorimeter. 4 Higgs production at the LHCThe coupling of the Higgs boson with SM particles is directly proportional to these particles' mass, meaning that the production of Higgs' is dominated by the mediation through the massive W and Z, as well as the more massive fermions. These heavier particles are created by means of radiation processes from the incoming quarks or gluons in the colliding beam protons. Gluons are present at great abundance, meaning that the dominant production process for the SM Higgs particle is though gluon fusion.

This is shown in Figure fig:Higgs productiona). The leading production process, cross section-wise, at the LHC is the gluon fusion production process. The next to leading process, vector-boson fusion (VBF), is the W or Z boson radiation emitted by the incoming quarks. These then go on to fuse and produce a Higgs boson (Fig. fig:Higgs productionb).

The final two leading contributions to Higgs production at the LHC are through the associated production of a Higgs with a W or a Z vector (Fig. fig:Higgs productionc), and with a t t ? pair (Figure fig:Higgs productiond). Theoretical perturbative QFT calculations for the Higgs boson production cross sections are used for the comparison of observed results with the theoretical expectations.

For this, next-to-next-to-leading order QCD and electroweak corrections have been included in the calculations.Figure fig:cross section shows the theoretical production cross sections for a SM Higgs at s of 8 TeV in function of the boson’s mass, showing that the gluon-fusion process globally dominates. 5 Higgs boson decaysAssuming a mass of m H =125 GeV , the Higgs boson decays promptly, within a time span of approximately 1 0 -22 seconds after its production. The decay branching ratios are function of the Higgs boson interaction strength to its decay products.

This interaction strength is closely related to the particle’s masses. Theoretical branching ratios can be seen in Fig fig:branching ratios. The decay into pairs of vector bosons, WW or ZZ, is dominant, given that these decays are kinematically allowed and both vectors are on shell ( m H >2 m W or m H >2m Z ). Given that m H >2 m t , decays to t t ? can reach up to a 20% branching ratio. Decays to fermions other than t t ? , such as H ? b b ? , only becomes relevant for Higgs masses less than 2 m W .For a Higgs boson with m H =125GeV the branching fractions for H ? b b ? and H ? ? ? reach about 56.9% and 6.

2%, respectively. For decays into vector bosons, at least of of the two has to be off-shell, as a lower mass virtual W* and Z* bosons, which then go on to decay promptly. Calculations for the branching ratios into WW* and ZZ* result in 22.3% and 2.

8%, respectively. Finally, at a branching branching ratio of 0.23%, a possibility are decays into a pair of photons (diphoton decay) via loop processes involving heavier charged particles.