Fixed target Drell-Yan data and NNLO QCD fits of parton distribution functions

We discuss the influence of fixed target Drell-Yan data on the extraction of parton distribution functions at next-to-next-to-leading order (NNLO) in QCD. When used in a parton distribution fit, the Drell-Yan (DY) data constrain sea quark distributions at large values of Bjorken x. We find that not all available DY data are useful for improving the precision of parton distribution functions (PDFs) obtained from a fit to the deep inelastic scattering (DIS) data. In particular, some inconsistencies between DIS-based parton distribution functions and DY data for large values of dilepton rapidity are found. However, by selecting a sample of the DY data that is both representative and consistent with the DIS data, we are able to perform a combined PDF fit that significantly improves the precision of non-strange quark distributions at large values of x. The NNLO QCD corrections to the DY process are crucial for improving the precision. They reduce the uncertainty of the theoretical prediction, making it comparable to the experimental uncertainty in DY cross-sections over a broad range of x.Comment: 12 pages, revte

Direct collider signatures of large extra dimensions

The realization of low (TeV) scale strings usually requires the existence of large (TeV) extra dimensions where gauge bosons live. The direct production of Kaluza-Klein excitations of the photon and Z-boson at present and future colliders is studied in this work. At the LEPII, NLC and Tevatron colliders, these Kaluza-Klein modes lead to deviations from the standard model cross-sections, which provide lower bounds on their mass. At the LHC the corresponding resonances can be produced and decay on-shell, triggering a characteristic pattern in the distribution of the dilepton invariant mass.Comment: 14 pages, LateX, 5 figure

Puusta valmistettujen tuotteiden hiilivaraston muutoksen laskenta kasvihuonekaasuinventaariossa : Menetelmäkehitys Suomen kasvihuonekaasuinventaarioon

Tämän tutkimuksen päätavoite oli kehittää puutuotelaskentamenetelmä, jolla voidaan tuottaa estimaatit Suomen kasvihuonekaasujen inventaarioraportointiin. Laskentamenetelmän oli perustuttava ilmastosopimuksen ja Kioton pöytäkirjan osapuolikokousten päätöksiin. Tässä tutkimuksessa puutuotteilla tarkoitetaan puusta valmistettuja puolivalmisteita, joita ovat sahatavara, puulevyt, paperi ja kartonki sekä muut puolivalmisteet, kuten hirret ja puhelinpylväät. Kioton pöytäkirjan laskennassa puutuotteiden alkuperän selvittäminen oli yksi tärkeimmistä tavoitteista. Alkuperällä tarkoitetaan tässä tapauksessa sitä, onko puutuotteisiin käytetty puu peräisin Kioton pöytäkirjan aktiviteeteistä (metsänhoito, metsitys, metsänhävitys) vai näiden kolmen luokan ulkopuolisilta alueilta. Tavoitteena oli arvioida hakkuupoistumat näissä luokissa vuodesta 1990 alkaen. Tutkimuksessa tuotettiin erilaisilla laskentavaihtoehdoilla aikasarjat ilmastosopimuksen ja Kioton pöytäkirjan mukaisiin laskentoihin käyttäen tuotantoon perustuvaa laskentaa, jossa huomioidaan kotimaassa tuotetut ja vientiin menneet puutuotteet, jotka on valmistettu kotimaisesta puusta. Laskennan luotettavuutta saatiin parannettua kokoamalla vuosia 1900–1960 koskeva kansallinen aineisto sekä selvittämällä suomalaisille puutuotteille soveltuvat kansalliset hiilenmuuntokertoimet. Sahatavara, puulevyt ja puumassat (paperin ja kartongin hiilitaseiden arvioimiseksi) jaettiin laskennassa mielekkäisiin alaryhmiin, jotta puutuotteiden hiilitaseista saataisiin luotettavammat tulokset. Laskennassa käytettiin kullekin alaryhmälle sopivia hiilenmuuntokertoimia, ja kullekin puutuoteryhmälle omia kotimaisuusasteitaan. Tutkimuksen tulokset antavat tietoa siitä, kuinka puutuotteet on tarkoituksenmukaisinta laskea Suomen kasvihuonekaasuinventaariossa ottaen huomioon ilmastosopimuksen päätösten ja IPCC:n raportointiohjeiden asettamat vaatimukset.201

Production of Kaluza-Klein States at Future Colliders

Perturbative breaking of supersymmetry in four-dimensional string theories predict in general the existence of new large dimensions at the TeV scale. Such large dimensions lie in a domain of energies accessible to particle accelerators. Their main signature is the production of Kaluza-Klein excitations which can be detected at future colliders. We study this possibility for hadron colliders (TEVATRON, LHC) and $e^+ e^-$ colliders (LEP-200, NLC-500).Comment: 13 pages, LATEX, 4 postscript figures appended at the end, CPTH-A293.0294 and IEM-FT-84/9

Next-to-Next-to-Leading Order Higgs Production at Hadron Colliders

The Higgs boson production cross section at pp and p\bar{p} colliders is calculated in QCD at next-to-next-to-leading order (NNLO). We find that the perturbative expansion of the production cross section is well behaved and that scale dependence is reduced relative to the NLO result. These findings give us confidence in the reliability of the prediction. We also report an error in the NNLO correction to Drell-Yan production.Comment: 5 pages, 4 figures, minor change

Z-prime Gauge Bosons at the Tevatron

We study the discovery potential of the Tevatron for a Z-prime gauge boson. We introduce a parametrization of the Z-prime signal which provides a convenient bridge between collider searches and specific Z-prime models. The cross section for p pbar -> Z-prime X -> l^+ l^- X depends primarily on the Z-prime mass and the Z-prime decay branching fraction into leptons times the average square coupling to up and down quarks. If the quark and lepton masses are generated as in the standard model, then the Z-prime bosons accessible at the Tevatron must couple to fermions proportionally to a linear combination of baryon and lepton numbers in order to avoid the limits on Z--Z-prime mixing. More generally, we present several families of U(1) extensions of the standard model that include as special cases many of the Z-prime models discussed in the literature. Typically, the CDF and D0 experiments are expected to probe Z-prime-fermion couplings down to 0.1 for Z-prime masses in the 500--800 GeV range, which in various models would substantially improve the limits set by the LEP experiments.Comment: 34 pages, 13 figure

Three-loop non-diagonal current correlators in QCD and NLO corrections to single-top-quark production

The non-diagonal correlators of vector and scalar currents are considered at three-loop order in QCD. The full mass dependence is computed in the case where one of the quarks is massless and the other one carries the mass $M$. As applications we consider the single-top-quark production via the process $q\bar{q}\to t\bar{b}$ and the decay rate of a charged Higgs into hadrons. In both cases the computed NLO corrections are shown to be numerically much less important than the leading ones.Comment: 13 page

Complexity of the Ruminococcus flavefaciens FD-1 cellulosome reflects an expansion of family-related protein-protein interactions

This work was supported in part by the European Union, Area NMP.2013.1.1–2: Self-assembly of naturally occurring nanosystems: CellulosomePlus Project number: 604530, and by the EU Seventh Framework Programme (FP7 2007–2013) under the WallTraC project (Grant Agreement no 263916), and BioStruct-X (grant agreement no 283570). This paper reflects the author’s views only. The European Community is not liable for any use that may be made of the information contained herein. CMGAF is also supported by Fundação para a Ciência e a Tecnologia (Lisbon, Portugal) through grants PTDC/BIA-PRO/103980/2008 and EXPL/BIA-MIC/1176/2012. EAB is also funded by a grant (No. 1349/13) from the Israel Science Foundation (ISF), Jerusalem, Israel and by a grant (No. 2013284) from the U.S.-Israel Binational Science Foundation (BSF). E.A.B. is the incumbent of The Maynard I. and Elaine Wishner Chair of Bio-organic Chemistry.Peer reviewedPublisher PD

h→μτh\to \mu\tau at Hadron Colliders

We study the observability for a lepton flavor-changing decay of a Higgs boson $h\to \mu\tau$ at hadron colliders. Flavor-changing couplings of a Higgs boson exist at tree level in models with multiple Higgs doublets. The $h\mu\tau$ coupling is particularly motivated by the favorable intepretation of $\nu_\mu-\nu_\tau$ oscillation. We find that at the Tevatron Run II the unique $\mu\tau$ signature could serve as the Higgs discovery channel, surpassing expectations for Higgs boson searches in the SM and in a large parameter region of the MSSM. The sensitivity will be greatly improved at the LHC, beyond the coverage at a muon collider Higgs factory.Comment: Version to appear in PR