1. 
 Hudson, Lawrence N., et al.
(författare)

The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project
 2017

Ingår i: Ecology and Evolution.  : Wiley Open Access.  20457758 . 20457758. ; 7:1, s. 145188

Tidskriftsartikel (refereegranskat)abstract
 The PREDICTS projectProjecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.


2. 
 Aaron, F. D., et al.
(författare)

Combined measurement and QCD analysis of the inclusive e(+/)p scattering cross sections at HERA
 2010

Ingår i: Journal of High Energy Physics.  : Springer.  10298479. ; :1

Tidskriftsartikel (refereegranskat)abstract
 A combination is presented of the inclusive deep inelastic cross sections measured by the H1 and ZEUS Collaborations in neutral and charged current unpolarised e(+/)p scattering at HERA during the period 19942000. The data span six orders of magnitude in negative fourmomentumtransfer squared, Q(2), and in Bjorken x. The combination method used takes the correlations of systematic uncertainties into account, resulting in an improved accuracy. The combined data are the sole input in a NLO QCD analysis which determines a new set of parton distributions, HERAPDF1.0, with small experimental uncertainties. This set includes an estimate of the model and parametrisation uncertainties of the fit result.


3. 
 Aaron, F. D., et al.
(författare)

Events with an isolated lepton and missing transverse momentum and measurement of W production at HERA
 2010

Ingår i: Journal of High Energy Physics.  : Springer.  10298479. ; 2010:3, s. 119

Tidskriftsartikel (refereegranskat)abstract
 A search for events containing an isolated electron or muon and missing trans verse momentum produced in e(+/)p collisions is performed with the H1 and ZEUS detectors at HERA. The data were taken in the period 19942007 and correspond to an integrated luminosity of 0.98 fb(1). The observed event yields are in good overall agreement with the Standard Model prediction, which is dominated by single W production. In the e(+)p data, at large hadronic transverse momentum PT(X) > 25GeV, a total of 23 events are observed compared to a prediction of 14.0 +/ 1.9. The total single W boson production cross section is measured as 1.06 +/ 0.16 (stat.) +/ 0.07 (sys.) pb, in agreement with an Standard Model (SM) expectation of 1.26 +/ 0.19 pb.


4. 
 Aaron, F. D., et al.
(författare)

Multileptons with high transverse momentum at HERA
 2009

Ingår i: Journal of High Energy Physics.  : Springer.  10298479. ; :10

Tidskriftsartikel (refereegranskat)abstract
 Events with at least two high transverse momentum leptons (electrons or muons) are studied using the H1 and ZEUS detectors at HERA with an integrated luminosity of 0.94 fb(1). The observed numbers of events are in general agreement with the Standard Model predictions. Seven di and trilepton events are observed in e(+)p collision data with a scalar sum of the lepton transverse momenta above 100 GeV while 1.94 +/ 0.17 events are expected. Such events are not observed in e()p collisions for which 1.19 +/ 0.12 are predicted. Total visible and differential dielectron and dimuon photoproduction cross sections are extracted in a restricted phase space dominated by photonphoton collisions.


5. 
 Aktas, A, et al.
(författare)

A direct search for stable magnetic monopoles produced in positronproton collisions at HERA
 2005

Ingår i: European Physical Journal C. Particles and Fields.  : Springer.  14346044. ; 41, s. 133141

Tidskriftsartikel (refereegranskat)abstract
 A direct search has been made for magnetic monopoles produced in e(+)p collisions at a centre of mass energy of 300 GeV at HERA. The beam pipe surrounding the interaction region in 19951997 was investigated using a SQUID magnetometer to look for stopped magnetic monopoles. During this time an integrated luminosity of 62 pb(1) was delivered. No magnetic monopoles were observed and charge and mass dependent upper limits on the e(+)p production cross section are set.


6. 
 Aktas, A., et al.
(författare)

Elastic J/psi production at HERA
 2006

Ingår i: European Physical Journal C. Particles and Fields.  : Springer.  14346044. ; 46:3, s. 585603

Tidskriftsartikel (refereegranskat)abstract
 Cross sections for elastic production of J/psi mesons in photoproduction and electroproduction are measured in electron proton collisions at HERA using an integrated luminosity of 55 pb(1). Results are presented for photon virtualities Q(2) up to 80 GeV2. The dependence on the photonproton centre of mass energy Wgamma p is analysed in the range 40 <= Wgamma p <= 305 GeV in photoproduction and 40 <= Wgamma p <= 160 GeV in electroproduction. The Wgamma p dependences of the cross sections do not change significantly with Q(2) and can be described by models based on perturbative QCD. Within such models, the data show a high sensitivity to the gluon density of the proton in the domain of low Bjorken x and low Q(2). Differential cross sections d sigma/dt, where t is the squared fourmomentum transfer at the proton vertex, are measured in the range vertical bar t vertical bar < 1.2 GeV2 as functions of Wgamma p and Q(2). Effective Pomeron trajectories are determined for photoproduction and electroproduction. The J/psi production and decay angular distributions are consistent with schannel helicity conservation. The ratio of the cross sections for longitudinally and transversely polarised photons is measured as a function of Q(2) and is found to be described by perturbative QCD based models.


7. 
 Aktas, A., et al.
(författare)

Measurement of event shape variables in deepinelastic scattering at HERA
 2006

Ingår i: European Physical Journal C. Particles and Fields.  : Springer.  14346044. ; 46:2, s. 343356

Tidskriftsartikel (refereegranskat)abstract
 Deepinelastic ep scattering data taken with the H1 detector at HERA and corresponding to an integrated luminosity of 106 pb(1) are used to study the differential distributions of event shape variables. These include thrust, jet broadening, jet mass and the Cparameter. The fourmomentum transfer Q is taken to be the relevant energy scale and ranges between 14 GeV and 200 GeV. The event shape distributions are compared with perturbative QCD predictions, which include resummed contributions and analytical power law corrections, the latter accounting for nonperturbative hadronisation effects. The data clearly exhibit the running of the strong coupling alpha(s)(Q) and are consistent with a universal power correction parameter alpha(0) for all event shape variables. A combined QCD fit using all event shape variables yields alpha(s)(m(Z)) = 0.1198 +/ 0.0013 (+0.0056)(0.0043) and alpha(0) = 0.476 +/ 0.008 (+0.018)(0.059).


8. 
 Aktas, A., et al.
(författare)

Diffractive deepinelastic scattering with a leading proton at HERA
 2006

Ingår i: European Physical Journal C. Particles and Fields.  : Springer.  14346044. ; 48:3, s. 749766

Tidskriftsartikel (refereegranskat)abstract
 The cross section for the diffractive deepinelastic scattering process ep > eX(P) is measured, with the leading final state proton detected in the H1 Forward Proton Spectrometer. The data analysed cover the range x(P) < 0.1 in fractional proton longitudinal momentum loss, 0.08 < vertical bar t vertical bar < 0.5 GeV2 in squared fourmomentum transfer at the proton vertex, 2 < Q(2) < 50 GeV2 in photon virtuality and 0.004 < beta = x/x(P) < 1, where x is the Bjorken scaling variable. For x(P) less than or similar to 10(2), the differential cross section has a dependence of approximately d sigma/dt proportional to e(6t), independently of x(P), beta and Q(2) within uncertainties. The cross section is also measured triple differentially in x(P), beta and Q(2). The x(P) dependence is interpreted in terms of an effective pomeron trajectory with intercept alpha(P) (0) = 1.114 +/ 0.018(stat.) +/ 0.012(syst.)(0.020)(+0.040) (model) and a subleading exchange. The data are in good agreement with an H1 measurement for which the event selection is based on a large gap in the rapidity distribution of the final state hadrons, after accounting for proton dissociation contributions in the latter. Within uncertainties, the dependence of the cross section on x and Q(2) can thus be factorised from the dependences on all studied variables which characterise the proton vertex, for both the pomeron and the subleading exchange.


9. 
 Aktas, A., et al.
(författare)

Forward jet production in deep inelastic scattering at HERA
 2006

Ingår i: European Physical Journal C. Particles and Fields.  : Springer.  14346044. ; 46:1, s. 2742

Tidskriftsartikel (refereegranskat)abstract
 The production of forward jets has been measured in deep inelastic ep collisions at HERA. The results are presented in terms of single differential cross sections as a function of the Bjorken scaling variable (xB(j)) and as triple differential cross sections d3 sigma/dx(Bj)dQ(2)dp(t)(,jet)(2), where Q(2) is the four momentum transfer squared and p(t)(,iet)(2) is the squared transverse momentum of the forward jet. Also cross sections for events with a dijet system in addition to the forward jet are measured as a function of the rapidity separation between the forward jet and the two additional jets. The measurements are compared with nexttoleading order QCD calculations and with the predictions of various QCDbased models.


10. 
 Aktas, A., et al.
(författare)

Measurement and QCD analysis of the diffractive deepinelastic scattering cross section at HERA
 2006

Ingår i: European Physical Journal C. Particles and Fields.  : Springer.  14346044. ; 48:3, s. 715748

Forskningsöversikt (refereegranskat)abstract
 A detailed analysis is presented of the diffractive deepinelastic scattering process ep > eXY, where Y is a proton or a low mass proton excitation carrying a fraction 1  x(IP) > 0.95 of the incident proton longitudinal momentum and the squared fourmomentum transfer at the proton vertex satisfies t < 1 GeV2. Using data taken by the H1 experiment, the cross section is measured for photon virtualities in the range 3.5 <= Q(2) <= 1600 GeV2, triple differentially in x(IP), Q(2) and beta = x/x(P), where x is the Bjorken scaling variable. At low x(IP), the data are consistent with a factorisable x(IP) dependence, which can be described by the exchange of an effective pomeron trajectory with intercept alpha(IP)(0) = 1.118 +/ 0.008(exp.)(0.010)(+0.029)(model). Diffractive parton distribution functions and their uncertainties are determined from a nexttoleading order DGLAP QCD analysis of the Q(2)and beta dependences of the cross section. The resulting gluon distribution carries an integrated fraction of around 70% of the exchanged momentum in the Q(2) range studied. Total and differential cross sections are also measured for the diffractive charged current process e(+) p > (v) over bar eXY and are found to be well described by predictions based on the diffractive parton distributions. The ratio of the diffractive to the inclusive neutral current ep cross sections is studied. Over most of the kinematic range, this ratio shows no significant dependence on Q(2) at fixed x(P) and x or on x at fixed Q(2) and beta.

