Search results for "Observable"
showing 10 items of 634 documents
Dispersion relation formalism for virtual Compton scattering of the proton
2001
We present in detail a dispersion relation formalism for virtual Compton scattering (VCS) off the proton from threshold into the $\Delta(1232)$-resonance region. Such a formalism can be used as a tool to extract the generalized polarizabilities of the proton from both unpolarized and polarized VCS observables over a larger energy range. We present calculations for existing and forthcoming VCS experiments and demonstrate that the VCS observables in the energy region between pion production threshold and the $\Delta(1232)$-resonance show an enhanced sensitivity to the generalized polarizabilities.
CP observables with spin-spin correlations in chargino production
2008
We study the CP-violating terms of the spin-spin correlations in chargino production e+e- -> chi^+/-_1 chi^-/+_2, and their subsequent two-body decays into sneutrinos plus leptons. We propose novel CP-sensitive observables with the help of T-odd products of the spin-spin terms. These terms depend on the polarizations of both charginos, with one polarization perpendicular to the production plane. We identify two classes of CP-sensitive observables; one requires the reconstruction of the production plane, the other not. Our framework is the Minimal Supersymmetric Standard Model with complex parameters.
From R_AA via correlations to jets - the long road to tomography
2009
The main motivation to investigate hard probes in heavy ion collisions is to do tomography, i.e. to infer medium properties from the in-medium modification of hard processes. Yet while the suppression of high P_T hadrons has been measured for some time, solid tomographic information is slow to emerge. This can be traced back to theoretical uncertainties and ambiguities in modelling both medium evolution and parton-medium interaction. Ways to overcome these difficulties are to constrain models better and to focus on more differential observables. Correlations of high P_T hadrons offer non-trivial information beyond what can be deduced from single hadron suppression. They reflect not only the…
Supersymmetric mass spectra and the seesaw type-I scale
2012
We calculate supersymmetric mass spectra with cMSSM boundary conditions and a type-I seesaw mechanism added to explain current neutrino data. Using published, estimated errors on SUSY mass observables for a combined LHC+ILC analysis, we perform a theoretical $\chi^2$ analysis to identify parameter regions where pure cMSSM and cMSSM plus seesaw type-I might be distinguishable with LHC+ILC data. The most important observables are determined to be the (left) smuon and selectron masses and the splitting between them, respectively. Splitting in the (left) smuon and selectrons is tiny in most of cMSSM parameter space, but can be quite sizeable for large values of the seesaw scale, $m_{SS}$. Thus,…
High energy resummation of jet observables
2017
In this paper we investigate the extension of high energy resummation at LLx accuracy to jet observables. In particular, we present the high energy resummed expression of the transverse momentum distribution of the outgoing parton in the general partonic process $g(q) + g(q) \to g(q) + X$. In order to reach this result, several new ideas are introduced and exploited. First we prove that LLx resummation is achieved by dressing with hard radiation an off-shell gluon initiated LO process even if its on-shell limit is vanishing or trivial. Then we present a gauge-invariant framework where these calculations can be performed by using the modern helicity techniques. Finally, we show a possible wa…
CP violation in decays of the lightest supersymmetric particle with bilinearly broken R parity
2002
Supersymmetric models with broken R-parity induced by lepton number violating terms provide a calculable framework for neutrino masses and mixings. Within models with bilinear R-parity breaking six new physical phases appear which are potential sources of novel CP-violating phenomena compared to the minimal supersymmetric extension of the standard model. We consider CP-violating observables in the decays of the lightest supersymmetric particle in this class of models. We show that: (i) Neutrino physics requires a strong correlation between three different pairs of phases, thus reducing the effective number of new phases to three. (ii) CP-violating phenomena in decays of the lightest supersy…
Minimal 3-loop neutrino mass models and charged lepton flavor violation
2020
We study charged lepton flavor violation for the three most popular 3-loop Majorana neutrino mass models. We call these models "minimal" since their particle content correspond to the minimal sets for which genuine 3-loop models can be constructed. In all the three minimal models the neutrino mass matrix is proportional to some powers of Standard Model lepton masses, providing additional suppression factors on top of the expected loop suppression. To correctly explain neutrino masses, therefore large Yukawa couplings are needed in these models. We calculate charged lepton flavor violating observables and find that the three minimal models survive the current constraints only in very narrow …
Present Status of b → sℓ + ℓ − Anomalies
2017
Abstract We discuss the observed deviations in b → s l + l − processes from the Standard Model predictions and present global fits for the New Physics description of these anomalies. We further investigate the stability of the global fits under different theoretical assumptions and suggest strategies and a number of observables to clear up the source of the anomalies.
Angular observables for spin discrimination in boosted diboson final states
2016
We investigate the prospects for spin determination of a heavy diboson resonance using angular observables. Focusing in particular on boosted fully hadronic final states, we detail both the differences in signal efficiencies and distortions of differential distributions resulting from various jet substructure techniques. We treat the 2 TeV diboson excess as a case study, but our results are generally applicable to any future discovery in the diboson channel. Scrutinizing ATLAS and CMS analyses at 8 TeV and 13 TeV, we find that the specific cuts employed in these analyses have a tremendous impact on the discrimination power between different signal hypotheses. We discuss modified cuts that c…
QED radiative corrections to Virtual Compton Scattering
2000
The QED radiative corrections to virtual Compton scattering (reaction $e p \to e p \gamma$) are calculated to first order in $\alpha_{em} \equiv e^2 / 4 \pi$. A detailed study is presented for the one-loop virtual corrections and for the first order soft-photon emission contributions. Furthermore, a full numerical calculation is given for the radiative tail, corresponding with photon emission processes, where the photon energy is not very small compared with the lepton momenta. We compare our results with existing works on elastic electron-proton scattering, and show for the $e p \to e p \gamma$ reaction how the observables are modified due to these first order QED radiative corrections. We…