We study bottom-quark fragmentation in
e
+
e
−
annihilation, top and Higgs decay
H
→
b
b
¯
, using Monte Carlo event generators, as well as calculations, based on the formalism of perturbative ...fragmentation functions, which resum soft- and collinear-radiation effects in the next-to-leading logarithmic approximation. We consider the PYTHIA and HERWIG generators, and implement matrix-element corrections to the parton shower simulation of the
H
→
b
b
¯
process in HERWIG. We tune the Kartvelishvili, string and cluster models to
B-hadron data from LEP and SLD, and present results in both
x
B
and moment spaces. The
B-hadron spectra yielded by HERWIG, PYTHIA and resummed calculations show small discrepancies, which are due to the different approaches and models employed and to the quality of the fits to the
e
+
e
−
data.
In order to get ready for physics at the LHC, the CMS experiment has to be
set up for data taking. The data have to be well understood before new physics
can be investigated. On the other hand, there ...are standard processes, well
known from previous experiments and from simulation, which will help to
understand the data of the detector in the early days of the LHC.
Nobody knows exactly what kind of Higgs physics will be unveiled when the
Large Hadron Collider is turned on. There could be one Standard Model Higgs
boson or five Higgs bosons as is the case in ...two-Higgs-doublet models; there
could be more exotic or even completely unexpected scenarios. In order to be
prepared for the LHC era, a solid understanding of Standard Model or
Standard-Model-like Higgs physics is necessary. The first goal is to discover
the Higgs boson. Afterwards it has to be proven that the new particle is indeed
a Higgs boson. The Higgs boson has to couple to mass and its spin has to be
zero. Additional observables, such as decay width or CP eigenvalue, help to
distinguish between different models. Due to an almost infinite variety of
models, another important goal is to prepare for all possible situations. For
example, Higgs bosons could be produced in decays of heavier particles, or
could decay to invisible particles. In the following, a selection of mainly new
studies by ATLAS and CMS is presented.
In order to get ready for physics at the LHC, the CMS experiment has to be set up for data taking. The data have to be well understood before new physics can be investigated. On the other hand, there ...are standard processes, well known from previous experiments and from simulation, which will help to understand the data of the detector in the early days of the LHC.
We have investigated the sensitivity of CMS for finding the Higgs boson in
the H0 -> bbbar channel. An excellent b-tagging performance and a good jet
resolution are the main requirements needed for a ...successful event selection.
In the Standard Model (SM), the ttbar H0 -> l+- nu qqbar bbbar bbbar channel is
accessible, if the Higgs mass is lighter than m(H0) = 125 GeV, already during
the first years of the LHC. Also, most of the MSSM (Minimal Supersymmetric
Standard Model) parameter space can be covered. The W+- H0 -> l+- nu bbbar
channel is only accessible with high luminosity at the LHC. In both channels
the mass can be determined with a precision of a few per cent and the Higgs
couplings at the level of 10%.
Nobody knows exactly what kind of Higgs physics will be unveiled when the Large Hadron Collider is turned on. There could be one Standard Model Higgs boson or five Higgs bosons as is the case in ...two-Higgs-doublet models; there could be more exotic or even completely unexpected scenarios. In order to be prepared for the LHC era, a solid understanding of Standard Model or Standard-Model-like Higgs physics is necessary. The first goal is to discover the Higgs boson. Afterwards it has to be proven that the new particle is indeed a Higgs boson. The Higgs boson has to couple to mass and its spin has to be zero. Additional observables, such as decay width or CP eigenvalue, help to distinguish between different models. Due to an almost infinite variety of models, another important goal is to prepare for all possible situations. For example, Higgs bosons could be produced in decays of heavier particles, or could decay to invisible particles. In the following, a selection of mainly new studies by ATLAS and CMS is presented.
We have investigated the sensitivity of CMS for finding the Higgs boson in the H0 -> bbbar channel. An excellent b-tagging performance and a good jet resolution are the main requirements needed for a ...successful event selection. In the Standard Model (SM), the ttbar H0 -> l+- nu qqbar bbbar bbbar channel is accessible, if the Higgs mass is lighter than m(H0) = 125 GeV, already during the first years of the LHC. Also, most of the MSSM (Minimal Supersymmetric Standard Model) parameter space can be covered. The W+- H0 -> l+- nu bbbar channel is only accessible with high luminosity at the LHC. In both channels the mass can be determined with a precision of a few per cent and the Higgs couplings at the level of 10%.
Eur.Phys.J.direct C3 (2001) N1 Two important properties of a Higgs boson are its mass and width. They may
distinguish the Standard Model (SM) Higgs boson from Higgs bosons of extended
models. We show ...results from a direct mass and width reconstruction for a Higgs
boson mass range from 120 to 340 GeV. The mass and width have been
reconstructed from the H --> ZZstar --> mu+mu-mu+mu- reaction in an LHC
simulation of the CMS detector. The determined mass accuracy has been compared
with that obtained from studies for a linear collider (LC). The mass precision
from the latter studies is derived by scaling previous LC simulation results
according to the expected event rates. For the Higgs boson width we compare a
direct determination with indirect methods and find good complementarity.
Two important properties of a Higgs boson are its mass and width. They may distinguish the Standard Model (SM) Higgs boson from Higgs bosons of extended models. We show results from a direct mass and ...width reconstruction for a Higgs boson mass range from 120 to 340 GeV. The mass and width have been reconstructed from the H --> ZZstar --> mu+mu-mu+mu- reaction in an LHC simulation of the CMS detector. The determined mass accuracy has been compared with that obtained from studies for a linear collider (LC). The mass precision from the latter studies is derived by scaling previous LC simulation results according to the expected event rates. For the Higgs boson width we compare a direct determination with indirect methods and find good complementarity.
We present a method how to detect the WH -> lnbb in the high luminosity LHC
environment with the CMS detector. This study is performed with fast detector
response simulation including high luminosity ...event pile up. The main aspects
of reconstruction are pile up jet rejection, identification of b-jets and
improvement of Higgs mass resolution.
The detection potential in the SM for m(H) < 130 GeV and in the MSSM is only
encouraging for high integrated luminosity. Nevertheless it is possible to
extract important Higgs parameters which are useful to elucidate the nature of
the Higgs sector. In combination with other channels, this channel provides
valuable information on Higgs boson couplings.
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