5,927 research outputs found
Normal tau polarisation as a sensitive probe of CP violation in chargino decay
CP violation in the spin-spin correlations in chargino production and
subsequent two-body decay into a tau and a tau-sneutrino is studied at the ILC.
From the normal polarisation of the tau, an asymmetry is defined to test the
CP-violating phase of the higgsino mass parameter \mu. Asymmetries of more than
\pm70% are obtained, also in scenarios with heavy first and second generation
sfermions. Bounds on the statistical significances of the CP asymmetries are
estimated. As a result, the normal tau polarisation in the chargino decay is
one of the most sensitive probes to constrain or measure the phase \phi_\mu at
the ILC, motivating further detailed experimental studies.Comment: 20 pages, 10 figures, gzipped tar fil
Physics Opportunities at mu+mu- Higgs Factories
We update theoretical studies of the physics opportunities presented by
mu+mu- Higgs factories. Interesting measurements of the Standard Model Higgs
decays into {\bar b}b, tau+tau- and WW* may be possible if the Higgs mass is
less than about 160 GeV, as preferred by the precision electroweak data, the
mass range being extended by varying appropriately the beam energy resolution.
A suitable value of the beam energy resolution would also enable the
uncertainty in the b-quark mass to be minimized, facilitating measurements of
parameters in the MSSM at such a first mu+mu- Higgs factory. These measurements
would be sensitive to radiative corrections to the Higgs-fermion-antifermion
decay vertices, which may violate CP. Radiative corrections in the MSSM may
also induce CP violation in Higgs-mass mixing, which can be probed via various
asymmetries measurable using polarized mu+mu- beams. In addition,
Higgs-chargino couplings may be probed at a second mu+mu- Higgs factory.Comment: Report of the Higgs factory working group of the ECFA-CERN study on
Neutrino Factory & Muon Storage Rings at CERN. 28 p
One-loop corrections to the chargino and neutralino mass matrices in the on-shell scheme
We present a consistent procedure for the calculation of the one-loop
corrections to the charginos and neutralinos by using their on-shell mass
matrices. The on-shell gaugino mass parameters M and M', and the Higgsino mass
parameter \mu are defined by the elements of these on-shell mass matrices. The
on-shell mass matrices are different by finite one-loop corrections from the
tree-level ones given in terms of the on-shell parameters. When the on-shell M
and \mu are determined by the chargino sector, the neutralino masses receive
corrections up to 4%. This must be taken into account in precision measurements
at future e^+ e^- linear colliders.Comment: One reference added, typo in eq. (20) correcte
Momentum asymmetries as CP violating observables
Three body decays can exhibit CP violation that arises from interfering
diagrams with different orderings of the final state particles. We construct
several momentum asymmetry observables that are accessible in a hadron collider
environment where some of the final state particles are not reconstructed and
not all the kinematic information can be extracted. We discuss the
complications that arise from the different possible production mechanisms of
the decaying particle. Examples involving heavy neutralino decays in
supersymmetric theories and heavy Majorana neutrino decays in Type-I seesaw
models are examined.Comment: 20 pages, 9 figures. Clarifying comments and one reference added,
matches published versio
SoLid : Search for Oscillations with Lithium-6 Detector at the SCK-CEN BR2 reactor
Sterile neutrinos have been considered as a possible explanation for the recent reactor and Gallium anomalies arising from reanalysis of reactor flux and calibration data of previous neutrino experiments. A way to test this hypothesis is to look for distortions of the anti-neutrino energy caused by oscillation from active to sterile neutrino at close stand-off (similar to 6-8m) of a compact reactor core. Due to the low rate of anti-neutrino interactions the main challenge in such measurement is to control the high level of gamma rays and neutron background.
The SoLid experiment is a proposal to search for active-to-sterile anti-neutrino oscillation at very short baseline of the SCK center dot CEN BR2 research reactor.
This experiment uses a novel approach to detect anti-neutrino with a highly segmented detector based on Lithium-6. With the combination of high granularity, high neutron-gamma discrimination using 6LiF:ZnS(Ag) and precise localization of the Inverse Beta Decay products, a better experimental sensitivity can be achieved compared to other state-of-the-art technology. This compact system requires minimum passive shielding allowing for very close stand off to the reactor. The experimental set up of the SoLid experiment and the BR2 reactor will be presented. The new principle of neutrino detection and the detector design with expected performance will be described. The expected sensitivity to new oscillations of the SoLid detector as well as the first measurements made with the 8 kg prototype detector deployed at the BR2 reactor in 2013-2014 will be reported
Les Houches "Physics at TeV Colliders 2003" Beyond the Standard Model Working Group: Summary Report
The work contained herein constitutes a report of the ``Beyond the Standard
Model'' working group for the Workshop "Physics at TeV Colliders", Les Houches,
France, 26 May--6 June, 2003. The research presented is original, and was
performed specifically for the workshop. Tools for calculations in the minimal
supersymmetric standard model are presented, including a comparison of the dark
matter relic density predicted by public codes. Reconstruction of
supersymmetric particle masses at the LHC and a future linear collider facility
is examined. Less orthodox supersymmetric signals such as non-pointing photons
and R-parity violating signals are studied. Features of extra dimensional
models are examined next, including measurement strategies for radions and
Higgs', as well as the virtual effects of Kaluza Klein modes of gluons. An LHC
search strategy for a heavy top found in many little Higgs model is presented
and finally, there is an update on LHC studies.Comment: 113 pages, ed B.C. Allanach, v5 has changes to part XV
Physics at the e+ e- Linear Collider
A comprehensive review of physics at an e+e- Linear Collider in the energy
range of sqrt{s}=92 GeV--3 TeV is presented in view of recent and expected LHC
results, experiments from low energy as well as astroparticle physics.The
report focuses in particular on Higgs boson, Top quark and electroweak
precision physics, but also discusses several models of beyond the Standard
Model physics such as Supersymmetry, little Higgs models and extra gauge
bosons. The connection to cosmology has been analyzed as well.Comment: 179 pages, plots and references updated, version to be published at
EPJ
Probing CP Violation with and without Momentum Reconstruction at the LHC
We study the potential to observe CP-violating effects in SUSY cascade decay
chains at the LHC. We consider squark and gluino production followed by
subsequent decays into neutralinos with a three-body leptonic decay in the
final step. Asymmetries composed by triple products of momenta of the final
state particles are sensitive to CP-violating effects. Due to large boosts
these asymmetries can be difficult to observe at a hadron collider. We show
that using all available kinematic information one can reconstruct the decay
chains on an event-by-event basis even in the case of 3-body decays, neutrinos
and LSPs in the final state. We also discuss the most important experimental
effects like major backgrounds and momentum smearing due to finite detector
resolution. We show that with 300 fb of collected data, CP violation may
be discovered at the LHC for a wide range of the phase of the bino mass
parameter .Comment: Version accepted for publication in JHEP. Clarifications added on the
assumptions used for plots. New references adde
Decays of the MSSM Higgs Bosons with Explicit CP Violation
We study Higgs boson decays in the minimal supersymmetric standard model
where the tree-level CP invariance of the Higgs potential is explicitly broken
by loop effects of soft CP-violating Yukawa interactions related to scalar
quarks of the third generation. The scalar-pseudoscalar mixing among two
neutral CP-even Higgs bosons and one CP-odd Higgs boson due to explicit CP
violation modifies their tree-level couplings to fermions, to the W^\pm and Z
bosons and to Higgs bosons themselves significantly. We analyze the
phenomenological impact of explicit CP violation on the branching ratios of the
neutral Higgs boson decays in detail and discuss how to directly confirm the
existence of explicit CP violation through \tau^+ \tau^- and t \bar{t} spin
correlations in the decays of the neutral Higgs bosons into a tau-lepton pair
and a top-quark pair.Comment: 28 pages, 10 figures, some references added and correcte
Toward High Precision Higgs-Boson Measurements at the International Linear e+e- Collider
This report reviews the properties of Higgs bosons in the Standard Model (SM)
and its various extensions. We give an extensive overview about the potential
of the ILC operated at centre-of-mass energies up to 1 TeV (including the gamma
gamma option) for the determination of the Higgs boson properties. This
comprises the measurement of the Higgs boson mass, its couplings to SM fermions
and gauge bosons, and the determination of the spin and the CP quantum numbers
of the Higgs. The extensions of the SM that are analyzed in more detail are
heavy SM-like Higgs bosons, heavy Higgs bosons in the framework of
Supersymmetry (SUSY) and further exotic scenarios. We review recent theoretical
developments in the field of Higgs boson physics. The important question what
the ILC can contribute to Higgs boson physics after the LHC, the LHC/ILC
interplay and synergy is discussed. The impact of Higgs boson physics on
cosmology in several SUSY frameworks is analyzed. The impact of the accelerator
and dector performance on the precision of measurements are discussed in
detail. We propose a strategy to optimize future analyses. Open questions
arising for the various topics are listed, further topics of study and
corresponding roadmaps are suggested.Comment: 128 pages, lots of figures. One subsection added and other minor
modification
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