#### Bounding the Higgs width at the LHC

- Event time: 3:00pm
- Event date: 14th March 2014
- Speaker: Richard Keith Ellis (Fermilab)
- Location: Higgs Centre Seminar Room, James Clerk Maxwell Building (JCMB) James Clerk Maxwell Building Peter Guthrie Tait Road Edinburgh EH9 3FD GB

### Event details

We describe the hadronic production of the four-lepton final state, e−e+μ−μ+, through the fusion of initial state gluons. This process is mediated by loops of quarks and we provide first full analytic results for helicity amplitudes that account for both the effects of the quark mass in the loop and off-shell vector bosons. The analytic results are both fast, and numerically stable in the region of low Z transverse momentum.

We use our results to study the interference between Higgs-mediated and continuum production of four-lepton final states, which is necessary in order to obtain accurate theoretical predictions outside the Higgs resonance region. We have confirmed and extended a recent analysis of Caola and Melnikov that proposes to use a measurement of the off-shell region to constrain the total width of the Higgs boson. Existing LHC data should bound the width at the level of 25–45 times the Standard Model expectation. We investigate the power of using a matrix element method to construct a kinematic discriminant to sharpen the constraint. The method is expected to give the best bound on the width of the Higgs boson, until the start of lepton collider operation.

#### Event resources

The Particle Physics Theory seminar is a weekly series of talks reflecting the diverse interests of the group. Topics include analytic and numerical calculations based on the Standard Model of elementary particle physics, theories exploring new physics, as well as more formal developments in gauge theories and gravity..