QCD corrections to forward-backward charge asymmetries in l- l+ j production at hadron colliders

The large cross sections for gauge boson production at the Fermilab Tevatron and the CERN Large Hadron Collider (LHC) might give a chance to determine the electroweak parameters with high precision. We calculated two different forward-backward charge asymmetries (A^CS_FB and A^j_FB) of lepton pairs in events with a large transverse momentum jet p p (pbar) -> Z, gamma* + j -> e- e+ j at next-to-leading order (NLO), O(alpha_s) corrections, making use of the Monte Carlo programs MCFM and ALPGEN. These observables could provide a new determination of the weak mixing angle sin^2 theta^lept_eff (M_Z^2) with a statistical precision for each lepton flavour of 10^{-3} (7 x 10^{-3}) at LHC (Tevatron). If b jets are identified, a new asymmetry with respect to the b quark (A^b_FB) can also be measured with a statistical precision of 2 x 10^{-3} (4 x 10^{-2}) at LHC (Tevatron). Finally, we comment on the dependence of our results on various sources of uncertainties and compare, in the case of A^b_FB, the exact result with an approximation that might be more suitable when performing a realistic experimental analysis.Comment: 5 pages, 1 figure, talk presentad by R. Pittau at the International Europhysics Conference on High Energy Physics, July 21st - 27th 2005, Lisbon, Portuga

WEXTER and ERAFITTER: two programs to fit M_W at LEP2 using the best measurable kinematical variables

In this paper, we present two programs to fit M_W at LEP2 using the best measurable kinematical variables. The theoretical probabilities of observing the final-state kinematical configurations are computed by integrating over the quantities that are not well measured. Therefore, an event-by-event kinematical reconstruction is avoided. M_W is then determined through a maximum likelihood fit.Comment: 19 pages, Latex fil

EXCALIBUR -- a Monte Carlo program to evaluate all four fermion processes at LEP 200 and beyond

A Monte Carlo program is presented that computes all four fermion processes in $e^+ e^-$ annihilation. QED initial state corrections and QCD contributions are included. Fermions are taken to be massless, allowing a very fast evaluation of the matrix element. A systematic, modular and self-optimizing strategy has been adopted for the Monte Carlo integration, that serves also as an example for further event generators in high energy particle physics.Comment: INLO-PUB-12/94, 24 pages including figures, Latex fil

Identification alone versus intraoperative neuromonitoring of the recurrent laryngeal nerve during thyroid surgery: experience of 2034 consecutive patients

Background: The aim of this study was to evaluate the ability of intraoperative neuromonitoring in reducing the postoperative recurrent laryngeal nerve palsy rate by a comparison between patients submitted to thyroidectomy with intraoperative neuromonitoring and with routine identification alone. Methods: Between June 2007 and December 2012, 2034 consecutive patients underwent thyroidectomy by a single surgical team. We compared patients who have had neuromonitoring and patients who have undergone surgery with nerve visualization alone. Patients in which neuromonitoring was not utilized (Group A) were 993, patients in which was utilized (group B) were 1041. Results: In group A 28 recurrent laryngeal nerve injuries were observed (2.82%), 21 (2.11%) transient and 7 (0.7%) permanent. In group B 23 recurrent laryngeal nerve injuries were observed (2.21%), in 17 cases (1.63%) transient and in 6 (0.58%) permanent. Differences were not statistically significative. Conclusions: Visual nerve identification remains the gold standard of recurrent laryngeal nerve management in thyroid surgery. Neuromonitoring helps to identify the nerve, in particular in difficult cases, but it did not decrease nerve injuries compared with visualization alone. Future studies are warranted to evaluate the benefit of intraoperative neuromonitoring in thyroidectomy, especially in conditions in which the recurrent nerve is at high risk of injury. Keywords: Neuromonitoring, Recurrent laryngeal nerve, Thyroidectom

Numerical Evaluation of Six-Photon Amplitudes

We apply the recently proposed amplitude reduction at the integrand level method, to the computation of the scattering process 2 photons -> 4 photons, including the case of a massive fermion loop. We also present several improvements of the method, including a general strategy to reconstruct the rational part of any one-loop amplitude and the treatment of vanishing Gram-determinants.Comment: 21 pages, 3 figures. Version accepted for publication in JHE

Evaluating historical, basin-wide landslide activity in a context of land abandonment and climate change: Effects of landslide visibility and temporal resolution

Drainage basins of the Northern Apennines, particularly in the clayey settings, bear among the highest rates of landsliding worldwide. A history of major land cover changes has left a landscape characterized by sparse, coppice-managed forest, transitional shrubs, and actively eroding badlands. Historical trends of landslide occurrence are examined in the Sillaro River basin (139 km2) in relation to land cover and climatic changes. To this purpose we have compiled a multi-temporal (1954–2018) landslide inventory (n = 1164) across twelve sequential photo sets that bears decadal (7- to 15-yr) and finer (2- to 6-yr) temporal resolution respectively before and after 1996. To account for changes in meteorological forcing, we examine: (i) the total annual precipitation (PRCPTOT); (ii) the annual maximum daily precipitation (RX1day); and (iii) the precipitation fraction (R99pTOT) due to extremely wet days. We find that landslide activity is strongly controlled by lithology, with landslide densities in claystones 3-to-4 times higher than in marl-sandstone alternations. This difference is chiefly associated with badlands, which are the most active land cover type and where new scars at a site could recur up to nine times. To evaluate the influence of varying temporal resolution on inventory completeness, hence on inference about land cover and climatic effects, we constrain the time scales of landslide visibility and assess the relative rates of undersampling. We find that visibility functions decline non-linearly with time, and that an inventory compiled at 5-year resolution would be missing up to 20 % of the landslide scars, with the size of an additional 27 % that would be underestimated due to revegetation. Overall, detection of entire landslide scars, which varies with land cover, becomes rare after 13 years in transitional shrubs, and after 17 years in badlands and managed forest. The historical analysis shows that landslide count: (i) increases in 1955–1976, a period of maximum anthropogenic pressure and wetter conditions; (ii) decreases steadily from 1977 through 2000, during a phase of land abandonment and decline in annual precipitation; and (iii) grows highest in 2000–2014, a period of land cover stability characterized by lesser precipitation although increasingly focused on high-magnitude events. To evaluate the likely reason of this recent increase in landsliding (i.e., R99pTOT vs inventorying resolution), we replicate the post-1996 mapping at coarser resolution. In the simplified inventory, landslide densities drop up to a factor of 2, and the inverse correlation originally linking landslide count with R99pTOT, loses significance. We conclude that, when the bias associated with varying inventorying resolution is removed, dependencies previously attributed to climatic effects become drastically reduced, and in some instances can even disappear

On the determination of M_W and TGCs in W-pair production using the best measured kinematical variables

A study is made of the feasibility of maximum likelihood fits to determine M_W and triple gauge boson couplings using only those experimental kinematical variables that are well measured. A computational tool to calculate theoretical probabilities for those kinematical variables is discussed and then applied to samples of unweighted events produced by an event generator. Detailed results on the M_W determination for semileptonic final states in W-pair production show the feasibility of the method. For TGCs one result is presented as an illustration.Comment: 7 pages, Latex, 1 figure, published in Phys. Lett. B, reference added, misprint correcte

Algebraic reduction of one-loop Feynman graph amplitudes

An algorithm for the reduction of one-loop n-point tensor integrals to basic integrals is proposed. We transform tensor integrals to scalar integrals with shifted dimension and reduce these by recurrence relations to integrals in generic dimension. Also the integration-by-parts method is used to reduce indices (powers of scalar propagators) of the scalar diagrams. The obtained recurrence relations for one-loop integrals are explicitly evaluated for 5- and 6-point functions. In the latter case the corresponding Gram determinant vanishes identically for d=4, which greatly simplifies the application of the recurrence relations.Comment: 18 pages, 1 figure, added references, expanded introduction, improved tex