Showing papers in "European Physical Journal C in 2014"

The global electroweak fit at NNLO and prospects for the LHC and ILC

Abstract: For a long time, global fits of the electroweak sector of the standard model (SM) have been used to exploit measurements of electroweak precision observables at lepton colliders (LEP, SLC), together with measurements at hadron colliders (Tevatron, LHC) and accurate theoretical predictions at multi-loop level, to constrain free parameters of the SM, such as the Higgs and top masses. Today, all fundamental SM parameters entering these fits are experimentally determined, including information on the Higgs couplings, and the global fits are used as powerful tools to assess the validity of the theory and to constrain scenarios for new physics. Future measurements at the Large Hadron Collider (LHC) and the International Linear Collider (ILC) promise to improve the experimental precision of key observables used in the fits. This paper presents updated electroweak fit results using the latest NNLO theoretical predictions and prospects for the LHC and ILC. The impact of experimental and theoretical uncertainties is analysed in detail. We compare constraints from the electroweak fit on the Higgs couplings with direct LHC measurements, and we examine present and future prospects of these constraints using a model with modified couplings of the Higgs boson to fermions and bosons.

HiggsSignals: Confronting arbitrary Higgs sectors with measurements at the Tevatron and the LHC

Abstract: HiggsSignals is a Fortran90 computer code that allows to test the compatibility of Higgs sector predictions against Higgs rates and masses measured at the LHC or the Tevatron. Arbitrary models with any number of Higgs bosons can be investigated using a model-independent input scheme based on HiggsBounds. The test is based on the calculation of a $$\chi ^2$$ measure from the predictions and the measured Higgs rates and masses, with the ability of fully taking into account systematics and correlations for the signal rate predictions, luminosity and Higgs mass predictions. It features two complementary methods for the test. First, the peak-centered method, in which each observable is defined by a Higgs signal rate measured at a specific hypothetical Higgs mass, corresponding to a tentative Higgs signal. Second, the mass-centered method, where the test is evaluated by comparing the signal rate measurement to the theory prediction at the Higgs mass predicted by the model. The program allows for the simultaneous use of both methods, which is useful in testing models with multiple Higgs bosons. The code automatically combines the signal rates of multiple Higgs bosons if their signals cannot be resolved by the experimental analysis. We compare results obtained with HiggsSignals to official ATLAS and CMS results for various examples of Higgs property determinations and find very good agreement. A few examples of HiggsSignals applications are provided, going beyond the scenarios investigated by the LHC collaborations. For models with more than one Higgs boson we recommend to use HiggsSignals and HiggsBounds in parallel to exploit the full constraining power of Higgs search exclusion limits and the measurements of the signal seen at $$m_H\approx 125.5$$ GeV.

Tuning PYTHIA 8.1: the Monash 2013 tune

Abstract: We present an updated set of parameters for the PYTHIA 8 event generator. We reevaluate the constraints imposed by LEP and SLD on hadronization, in particular with regard to heavy-quark fragmentation and strangeness production. For hadron collisions, we combine the updated fragmentation parameters with the new NNPDF2.3 LO PDF set. We use minimum-bias, Drell–Yan, and underlying-event data from the LHC to constrain the initial-state-radiation and multi-parton-interaction parameters, combined with data from SPS and the Tevatron to constrain the energy scaling. Several distributions show significant improvements with respect to the current defaults, for both $$ee$$ and $$pp$$ collisions, though we emphasize that interesting discrepancies remain in particular for strange particles and baryons. The updated parameters are available as an option starting from PYTHIA 8.185, by setting Tune:ee = 7 and Tune:pp = 14.

HiggsBounds-4: improved tests of extended Higgs sectors against exclusion bounds from LEP, the Tevatron and the LHC

Abstract: We describe the new developments in version 4 of the public computer code HiggsBounds. HiggsBounds is a tool to test models with arbitrary Higgs sectors, containing both neutral and charged Higgs bosons, against the published exclusion bounds from Higgs searches at the LEP, Tevatron and LHC experiments. From the model predictions for the Higgs masses, branching ratios, production cross sections and total decay widths—which are specified by the user in the input for the program—the code calculates the predicted signal rates for the search channels considered in the experimental data. The signal rates are compared to the expected and observed cross section limits from the Higgs searches to determine whether a point in the model parameter space is excluded at 95 % confidence level. In this paper we present a modification of the HiggsBounds main algorithm that extends the exclusion test in order to ensure that it provides useful results in the presence of one or more significant excesses in the data, corresponding to potential Higgs signals. We also describe a new method to test whether the limits from an experimental search performed under certain model assumptions can be applied to a different theoretical model. Further developments discussed here include a framework to take into account theoretical uncertainties on the Higgs mass predictions, and the possibility to obtain the $$\chi ^2$$ likelihood of Higgs exclusion limits from LEP. Extensions to the user subroutines from earlier versions of HiggsBounds are described. The new features are demonstrated by additional example programs.

Observation of the diphoton decay of the Higgs boson and measurement of its properties

Abstract: Observation of the diphoton decay mode of the recently discovered Higgs boson and measurement of some of its properties are reported. The analysis uses the entire dataset collected by the CMS experiment in proton-proton collisions during the 2011 and 2012 LHC running periods. The data samples correspond to integrated luminosities of 5.1 inverse femtobarns at sqrt(s) = 7 TeV and 19.7 inverse femtobarns at 8 TeV. A clear signal is observed in the diphoton channel at a mass close to 125 GeV with a local significance of 5.7 sigma, where a significance of 5.2 sigma is expected for the standard model Higgs boson. The mass is measured to be 124.70 +/- 0.34 GeV = 124.70 +/- 0.31 (stat) +/- 0.15 (syst) GeV, and the best-fit signal strength relative to the standard model prediction is 1.14 +0.26/-0.23 = 1.14 +/- 0.21 (stat) +0.09/-0.05 (syst) +0.13/-0.09 (theo). Additional measurements include the signal strength modifiers associated with different production mechanisms, and hypothesis tests between spin-0 and spin-2 models.

QCD and strongly coupled gauge theories: challenges and perspectives

Abstract: We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to strongly coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.

The Physics of the B Factories

Abstract: This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C.

Electron and photon energy calibration with the ATLAS detector using LHC Run 1 data

Abstract: This paper presents the electron and photon energy calibration achieved with the ATLAS detector using about 25 fb(-1) of LHC proton-proton collision data taken at centre-of-mass energies of root s = 7 and 8 TeV. The reconstruction of electron and photon energies is optimised using multivariate algorithms. The response of the calorimeter layers is equalised in data and simulation, and the longitudinal profile of the electromagnetic showers is exploited to estimate the passive material in front of the calorimeter and reoptimise the detector simulation. After all corrections, the Z resonance is used to set the absolute energy scale. For electrons from Z decays, the achieved calibration is typically accurate to 0.05% in most of the detector acceptance, rising to 0.2% in regions with large amounts of passive material. The remaining inaccuracy is less than 0.2-1% for electrons with a transverse energy of 10 GeV, and is on average 0.3% for photons. The detector resolution is determined with a relative inaccuracy of less than 10% for electrons and photons up to 60 GeV transverse energy, rising to 40% for transverse energies above 500 GeV.

Searches for electroweak production of charginos, neutralinos, and sleptons decaying to leptons and W, Z, and Higgs bosons in pp collisions at 8 TeV

Abstract: Searches for the direct electroweak production of supersymmetric charginos, neutralinos, and sleptons in a variety of signatures with leptons and W, Z, and Higgs bosons are presented. Results are based on a sample of proton-proton collision data collected at center-of-mass energy sqrt(s) = 8 TeV with the CMS detector in 2012, corresponding to an integrated luminosity of 19.5 inverse femtobarns. The observed event rates are in agreement with expectations from the standard model. These results probe charginos and neutralinos with masses up to 720 GeV, and sleptons up to 260 GeV, depending on the model details.

Measurement of the muon reconstruction performance of the ATLAS detector using 2011 and 2012 LHC proton-proton collision data

Abstract: This paper presents the performance of the ATLAS muon reconstruction during the LHC run with pp collisions at root s = 7-8 TeV in 2011-2012, focusing mainly on data collected in 2012. Measurements ...

Electron reconstruction and identification efficiency measurements with the atlas detector using the 2011 lhc proton-proton collision data

Abstract: Many of the interesting physics processes to be measured at the LHC have a signature involving one or more isolated electrons. The electron reconstruction and identification efficiencies of the ATLAS detector at the LHC have been evaluated using proton-proton collision data collected in 2011 at TeV and corresponding to an integrated luminosity of 4.7 fb. Tag-and-probe methods using events with leptonic decays of and bosons and mesons are employed to benchmark these performance parameters. The combination of all measurements results in identification efficiencies determined with an accuracy at the few per mil level for electron transverse energy greater than 30 GeV.

Squark and gluino production cross sections in \(pp\) collisions at \(\sqrt{s} = 13, 14, 33\) and \(100\) TeV

Abstract: We present state-of-the-art cross section predictions for the production of supersymmetric squarks and gluinos at the upcoming LHC run with a centre-of-mass energy of [Formula: see text] and [Formula: see text] TeV, and at potential future [Formula: see text] colliders operating at [Formula: see text] and [Formula: see text] TeV. The results are based on calculations which include the resummation of soft-gluon emission at next-to-leading logarithmic accuracy, matched to next-to-leading order supersymmetric QCD corrections. Furthermore, we provide an estimate of the theoretical uncertainty due to the variation of the renormalisation and factorisation scales and the parton distribution functions.

Designing and recasting LHC analyses with MadAnalysis 5

Abstract: We present an extension of the expert mode of the MadAnalysis 5 program dedicated to the design or reinterpretation of high-energy physics collider analyses. We detail the predefined classes, functions and methods available to the user and emphasize the most recent developments. The latter include the possible definition of multiple sub-analyses and a novel user-friendly treatment for the selection criteria. We illustrate this approach by two concrete examples: a CMS search for supersymmetric partners of the top quark and a phenomenological analysis targeting hadronically decaying monotop systems.

Search for invisible decays of Higgs bosons in the vector boson fusion and associated ZH production modes

Abstract: A search for invisible decays of Higgs bosons is performed using the vector boson fusion and associated ZH production modes. In the ZH mode, the Z boson is required to decay to a pair of charged leptons or a $b\bar{b}$ quark pair. The searches use the 8 TeV pp collision dataset collected by the CMS detector at the LHC, corresponding to an integrated luminosity of up to 19.7 inverse femtobarns. Certain channels include data from 7 TeV collisions corresponding to an integrated luminosity of 4.9 inverse femtobarns. The searches are sensitive to non-standard-model invisible decays of the recently observed Higgs boson, as well as additional Higgs bosons with similar production modes and large invisible branching fractions. In all channels, the observed data are consistent with the expected standard model backgrounds. Limits are set on the production cross section times invisible branching fraction, as a function of the Higgs boson mass, for the vector boson fusion and ZH production modes. By combining all channels, and assuming standard model Higgs boson cross sections and acceptances, the observed (expected) upper limit on the invisible branching fraction at $m_H$=125 GeV is found to be 0.58 (0.44) at 95% confidence level. We interpret this limit in terms of a Higgs-portal model of dark matter interactions.

GoSam -2.0: a tool for automated one-loop calculations within the Standard Model and beyond

Abstract: We present the version 2.0 of the program package GoSam for the automated calculation of one-loop amplitudes. GoSam is devised to compute one-loop QCD and/or electroweak corrections to multi-particle processes within and beyond the Standard Model. The new code contains improvements in the generation and in the reduction of the amplitudes, performs better in computing time and numerical accuracy, and has an extended range of applicability. The extended version of the “Binoth-Les-Houches-Accord” interface to Monte Carlo programs is also implemented. We give a detailed description of installation and usage of the code, and illustrate the new features in dedicated examples.

Black Holes as Critical Point of Quantum Phase Transition

Abstract: We reformulate the quantum black hole portrait in the language of modern condensed matter physics. We show that black holes can be understood as a graviton Bose-Einstein condensate at the critical point of a quantum phase transition, identical to what has been observed in systems of cold atoms. The Bogoliubov modes that become degenerate and nearly gapless at this point are the holographic quantum degrees of freedom responsible for the black hole entropy and the information storage. They have no (semi)classical counterparts and become inaccessible in this limit. These findings indicate a deep connection between the seemingly remote systems and suggest a new quantum foundation of holography. They also open an intriguing possibility of simulating black hole information processing in table-top labs.

Boosted objects and jet substructure at the LHC. Report of BOOST2012, held at IFIC Valencia, 23rd-27th of July 2012

Abstract: This report of the BOOST2012 workshop presents the results of four working groups that studied key aspects of jet substructure We discuss the potential of first-principle QCD calculations to yield a precise description of the substructure of jets and study the accuracy of state-of-the-art Monte Carlo tools Limitations of the experiments’ ability to resolve substructure are evaluated, with a focus on the impact of additional (pile-up) proton proton collisions on jet substructure performance in future LHC operating scenarios A final section summarizes the lessons learnt from jet substructure analyses in searches for new physics in the production of boosted top quarks

Results on low mass WIMPs using an upgraded CRESST-II detector

Abstract: The CRESST-II cryogenic dark matter search aims for the detection of WIMPs via elastic scattering off nuclei in CaWO $$_4$$ crystals. We present results from a low-threshold analysis of a single upgraded detector module. This module efficiently vetoes low energy backgrounds induced by $$\alpha $$ -decays on inner surfaces of the detector. With an exposure of 29.35 kg live days collected in 2013 we set a limit on spin-independent WIMP-nucleon scattering which probes a new region of parameter space for WIMP masses below 3 GeV/c $$^2$$ , previously not covered in direct detection searches. A possible excess over background discussed for the previous CRESST-II phase 1 (from 2009 to 2011) is not confirmed.

SModelS: a tool for interpreting simplified-model results from the LHC and its application to supersymmetry

Abstract: We present a general procedure to decompose Beyond the Standard Model (BSM) collider signatures presenting a $$\mathbb {Z}_2$$ symmetry into Simplified Model Spectrum (SMS) topologies. Our method provides a way to cast BSM predictions for the LHC in a model independent framework, which can be directly confronted with the relevant experimental constraints. Our concrete implementation currently focusses on supersymmetry searches with missing energy, for which a large variety of SMS results from ATLAS and CMS are available. As show-case examples we apply our procedure to two scans of the minimal supersymmetric standard model. We discuss how the SMS limits constrain various particle masses and which regions of parameter space remain unchallenged by the current SMS interpretations of the LHC results.

Search for heavy neutrinos and W bosons with right-handed couplings in proton-proton collisions at sqrt(s) = 8 TeV

Abstract: A search for heavy, right-handed neutrinos, $$\mathrm {N}_{\ell }$$ ( $$\ell = \mathrm {e}, \mu $$ ), and right-handed $$\mathrm {W}_{\mathrm {R}}$$ bosons, which arise in the left-right symmetric extensions of the standard model, has been performed by the CMS experiment. The search was based on a sample of two lepton plus two jet events collected in proton–proton collisions at a center-of-mass energy of 8 $$\,\text {TeV}$$ corresponding to an integrated luminosity of 19.7 $$\mathrm{fb}^{-1}$$ . For models with strict left-right symmetry, and assuming only one $$\mathrm {N}_{\ell }$$ flavor contributes significantly to the $$\mathrm {W}_{\mathrm {R}}$$ decay width, the region in the two-dimensional $$(M_{\mathrm {W}_{\mathrm {R}}}, M_{\mathrm {N}_{\ell }})$$ mass plane excluded at a 95 % confidence level extends to approximately $$M_{\mathrm {W}_{\mathrm {R}}} = 3.0\,\text {TeV} $$ and covers a large range of neutrino masses below the $$\mathrm {W}_{\mathrm {R}}$$ boson mass, depending on the value of $$M_{\mathrm {W}_{\mathrm {R}}}$$ . This search significantly extends the $$(M_{\mathrm {W}_{\mathrm {R}}}, M_{\mathrm {N}_{\ell }})$$ exclusion region beyond previous results.

Aspects of the cosmological “coincidence problem”

Abstract: The observational fact that the present values of the densities of dark energy and dark matter are of the same order of magnitude, \(\rho _{\mathrm{de}0}/\rho _{\mathrm{dm}0} \sim \mathcal {O}(1)\), seems to indicate that we are currently living in a very special period of the cosmic history. Within the standard model, a density ratio of the order of one just at the present epoch can be seen as coincidental since it requires very special initial conditions in the early Universe. The corresponding “why now” question constitutes the cosmological “coincidence problem”. According to the standard model the equality \(\rho _{\mathrm{de}} = \rho _{\mathrm{dm}}\) took place “recently” at a redshift \(z \approx 0.55\). The meaning of “recently” is, however, parameter dependent. In terms of the cosmic time the situation looks different. We discuss several aspects of the “coincidence problem”, also in its relation to the cosmological constant problem, to issues of structure formation and to cosmic age considerations.

W^+W^-, WZ and ZZ production in the POWHEG-BOX-V2

Abstract: We present an implementation of the vector boson pair production processes $$ZZ$$ , $$W^+W^-$$ and $$WZ$$ within the POWHEG-BOX-V2. This implementation, derived from the POWHEG BOX version, has several improvements over the old one, among which the inclusion of all decay modes of the vector bosons, the possibility to generate different decay modes in the same run, speed optimization and phase space improvements in the handling of interference and singly resonant contributions.

A flavor kit for BSM models

Abstract: We present a new kit for the study of flavor observables in models beyond the standard model. The setup is based on the public codes SARAH and SPheno and allows for an easy implementation of new observables. The Wilson coefficients of the corresponding operators in the effective lagrangian are computed by SPheno modules written by SARAH. New operators can also be added by the user in a modular way. For this purpose a handy Mathematica package called the PreSARAH has been developed. This uses FeynArts and FormCalc to derive generic form factors at tree- and 1-loop levels and to generate the necessary input files for SARAH. This framework has been used to implement BR( $$\ell _{\alpha } \rightarrow \ell _{\beta } \gamma $$ ), BR( $$\ell _{\alpha } \rightarrow 3\, \ell _{\beta }$$ ), CR( $$\mu -e,A$$ ), BR( $$\tau \rightarrow P \, \ell $$ ), BR( $$h\rightarrow \ell _{\alpha } \ell _{\beta }$$ ), BR( $$Z\rightarrow \ell _{\alpha } \ell _{\beta }$$ ), BR( $$B_{s,d}^0 \rightarrow \ell \bar{\ell }$$ ), BR( $${\bar{B}} \rightarrow X_s\gamma $$ ), BR( $${\bar{B}} \rightarrow X_s \ell \bar{\ell }$$ ), BR( $${\bar{B}} \rightarrow X_{d,s} u {\bar{ u }}$$ ), BR( $$K^+ \rightarrow \pi ^+ u {\bar{ u }}$$ ), BR( $$K_L \rightarrow \pi ^0 u {\bar{ u }}$$ ), $$\varDelta M_{B_s,B_d}$$ , $$\varDelta M_K$$ , $$\varepsilon _K$$ , BR( $$B \rightarrow K \mu \bar{\mu }$$ ), BR( $$B\rightarrow \ell u $$ ), BR( $$D_s \rightarrow \ell u $$ ) and BR( $$K \rightarrow \ell u $$ ) in SARAH. Predictions for these observables can now be obtained in a wide range of SUSY and non-SUSY models. Finally, the user can use the same approach to easily compute additional observables.

P-V criticality of topological black holes in Lovelock-Born-Infeld gravity

Abstract: To understand the effect of third order Lovelock gravity, $$P$$ – $$V$$ criticality of topological AdS black holes in Lovelock–Born–Infeld gravity is investigated. The thermodynamics is further explored with some more extensions and in some more detail than the previous literature. A detailed analysis of the limit case $$\beta \rightarrow \infty $$ is performed for the seven-dimensional black holes. It is shown that, for the spherical topology, $$P$$ – $$V$$ criticality exists for both the uncharged and the charged cases. Our results demonstrate again that the charge is not the indispensable condition of $$P$$ – $$V$$ criticality. It may be attributed to the effect of higher derivative terms of the curvature because similar phenomenon was also found for Gauss–Bonnet black holes. For $$k=0$$ , there would be no $$P$$ – $$V$$ criticality. Interesting findings occur in the case $$k=-1$$ , in which positive solutions of critical points are found for both the uncharged and the charged cases. However, the $$P$$ – $$v$$ diagram is quite strange. To check whether these findings are physical, we give the analysis on the non-negative definiteness condition of the entropy. It is shown that, for any nontrivial value of $$\alpha $$ , the entropy is always positive for any specific volume $$v$$ . Since no $$P$$ – $$V$$ criticality exists for $$k=-1$$ in Einstein gravity and Gauss–Bonnet gravity, we can relate our findings with the peculiar property of third order Lovelock gravity. The entropy in third order Lovelock gravity consists of extra terms which are absent in the Gauss–Bonnet black holes, which makes the critical points satisfy the constraint of non-negative definiteness condition of the entropy. We also check the Gibbs free energy graph and “swallow tail” behavior can be observed. Moreover, the effect of nonlinear electrodynamics is also included in our research.

A realistic pattern of lepton mixing and masses from S_4 and CP

Abstract: We present a supersymmetric model with the flavour symmetry $$S_4 \times Z_3$$ and a CP symmetry which are broken to a $$Z_3$$ subgroup of the flavour symmetry in the charged lepton sector and to $$Z_2 \times $$ CP ( $$\times Z_3$$ ) in the neutrino one at leading order. This model implements an approach capable of predicting lepton mixing angles and Dirac as well as Majorana phases in terms of one free parameter. This parameter, directly related to the size of the reactor mixing angle $$\theta _{13}$$ , can be naturally of the correct order in our model. Atmospheric mixing is maximal, while $$\sin ^2 \theta _{12} \gtrsim 1/3$$ . All three phases are predicted: the Dirac phase is maximal, whereas the two Majorana phases are trivial. The neutrino mass matrix contains only three real parameters at leading order and neutrino masses effectively only depend on two of them. As a consequence, they have to be normally ordered and the absolute neutrino mass scale and the sum of the neutrino masses are predicted. The vacuum of the flavons can be correctly aligned. We study subleading corrections to the leading order results and show that they are small.

The CMSSM and NUHM1 after LHC Run 1

Abstract: WeanalyzetheimpactofdatafromthefullRun1 of the LHC at 7 and 8 TeV on the CMSSM with μ> 0 and 0, incorporating the constraints imposed by other experiments such as precision electroweak measurements, flavour measurements, the cos- mological density of cold dark matter and the direct search for the scattering of dark matter particles in the LUX exper- iment. We use the following results from the LHC experi- ments: ATLAS searches for events with E /T accompanied by jets with the full 7 and 8 TeV data, the ATLAS and CMS measurements of the mass of the Higgs boson, the CMS searches for heavy neutral Higgs bosons and a combination of the LHCb and CMS measurements of BR(Bs → μ + μ − ) and BR(Bd → μ + μ − ). Our results are based on samplings of the parameter spaces of the CMSSM for both μ> 0 and μ 0 with 6.8×10 6 , 6.2×10 6 and 1.6×10 7 points, respectively, obtained using the MultiNest tool. The impact of the Higgs-mass con- straint is assessed usingFeynHiggs 2.10.0, which pro- vides an improved prediction for the masses of the MSSM Higgs bosons in the region of heavy squark masses. It yields in general larger values of Mh than previous versions of FeynHiggs, reducing the pressure on the CMSSM and NUHM1. We find that the global χ 2 functions for the super- symmetric models vary slowly over most of the parameter

Single meson contributions to the muon’s anomalous magnetic moment

Abstract: We develop the formalism to provide an improved estimate for the hadronic light-by-light correction to the muon’s anomalous magnetic moment $$a_\mu $$ , by considering single meson contributions beyond the leading pseudoscalar mesons. We incorporate available experimental input as well as constraints from light-by-light scattering sum rules to estimate the effects of axial-vector, scalar, and tensor mesons. We give numerical evaluations for the hadronic light-by-light contribution of these states to $$a_\mu $$ . The presented formalism allows one to further improve on these estimates, once new data for such meson states will become available.

Perturbative QCD correlations in multi-parton collisions

Abstract: We examine the role played in double-parton interactions (DPI) by the parton–parton correlations originating from perturbative QCD parton splittings. Also presented are the results of the numerical analysis of the integrated DPI cross sections at Tevatron and LHC energies. To obtain the numerical results the knowledge of the single-parton GPDs gained by the HERA experiments was used to construct the non-perturbative input for generalized double-parton distributions. The perturbative two-parton correlations induced by three-parton interactions contribute significantly to a resolution of the longstanding puzzle of an excess of multi-jet production events in the back-to-back kinematics observed at the Tevatron.

Update of the ALEPH non-strange spectral functions from hadronic \tau decays

Abstract: An update of the ALEPH non-strange spectral functions from hadronic decays is presented. Compared to the 2005 ALEPH publication, the main improvement is related to the use of a new method to unfold the measured mass spectra from detector effects. This procedure also corrects a previous problem in the correlations between the unfolded mass bins. Results from QCD studies and for the evaluation of the hadronic vacuum polarisation contribution to the anomalous muon magnetic moment are derived using the new spectral functions. They are found in agreement with published results based on the previous set of spectral functions.

Fastlim : a fast LHC limit calculator

Abstract: Fastlim is a tool to calculate conservative limits on extensions of the Standard Model from direct LHC searches without performing any Monte Carlo event generation. The program reconstructs the visible cross sections (cross sections after event selection cuts) from pre-calculated efficiency tables and cross section tables for simplified event topologies. As a proof of concept of the approach, we have implemented searches relevant for supersymmetric models with R-parity conservation. Fastlim takes the spectrum and coupling information of a given model point and provides, for each signal region of the implemented analyses, the visible cross sections normalised to the corresponding upper limit, reported by the experiments, as well as the [Formula: see text] value. To demonstrate the utility of the program we study the sensitivity of the recent ATLAS missing energy searches to the parameter space of natural SUSY models. The program structure allows the straightforward inclusion of external efficiency tables and can be generalised to R-parity violating scenarios and non-SUSY models. This paper serves as a self-contained user guide and indicates the conventions and approximations used.