Why do we need higher-order fully exclusive Monte Carlo generator for Higgs boson production from heavy quark fusion at LHC?

Abstract

In this paper we argue that having available higher order fully exclusive Monte Carlo generator for Higgs boson production from heavy quark fusion will be mandatory for data analysis at LHC. The H → τ τ channel, a key for early discovery of the Higgs boson in the MSSM scenario, is discussed. With simplified example and for m H = 120 GeV we show, that depending on choice among presently available approaches, used for simulation of Higgs boson production from bbH Yukawa coupling, final acceptance for the signal events being reconstructed inside mass window may differ by a factor of 3. The spread is even larger (up to a factor of 10) for other production mechanisms (promising for some regions of the MSSM parameter space). The complete analysis, which necessarily will add stringent requirements for background rejection (such as identification of b-jet or veto on b-jet) and which will require statistical combination of samples selected with different selection criteria may only enhance the uncertainty.

Universal interface of TAUOLA: Technical and physics documentation

“…Unfortunately this strategy is limited, as it leaves little room for cases where theory and experimental effects are convoluted: size and even nature of the theoretical corrections depend on the experimental conditions. Such discussion on observables involving τ decays can be found in [2]. Recently, discussion for the physics of τ production and decay at low energies where similar aspects are addressed, was presented in [3].…”

“…Other building blocks may be less interesting, nonetheless they may affect the results of measurements. This is certainly true in the case of the underlying event or missing transverse energy or p T distributions generated from parton showers [2]. It may also be the case for QED final state bremsstrahlung or initial-final state interference (where potential difficulties may be expected [5] and predictions may need to be fixed with the help of experimental data).…”

“…The main class of TAUOLA C++ Universal Interface is called Tauola 2. PHOTOS was distributed together with TAUOLA since ref [9]…”

Parametrization of the QCD coupling in the Evolution Equations

“…The minus sign of the α s -argument in Eq. (7) indicates explicitly that the argument is space-like and for the space-like argument α s is given by the well-known expression:…”

“…[5] we argued that one of the easiest ways of treating α s in the BS equation could be the use of the Mellin transform. Nevertheless by various reasons, for example for Monte-Carlo simulations [6] and for performing the numerical calculations in the way convenient for experimentalists [7], one may prefer not to involve this operation. To this end, in the present paper we examine the treatment of α s in the Bethe-Salpeter equations without using the Mellin transform.…”