Inelastic, non-diffractive and diffractive proton-proton cross-section measurements at the LHC

The energy dependence of the rates and cross-sections of proton-proton interactions is of high importance both for collider physics and astroparticle physics. These quantities cannot be calculated from perturbative quantum chromodynamics, which has led to the development of several different models and parametrisations, and further measurements are needed to improve them and to test their validity. The inelastic rate for proton-proton interactions was measured at 2.76, 7 and 8 TeV center of mass energies using the T1 and T2 detectors of the TOTEM experiment at the LHC. Total and inelastic cross-sections were obtained using the Optical Theorem and measuring the inelastic and elastic rates simultaneously. The inelastic cross-sections 62.8 ± 2.9 mb at 2.76 TeV, 72.9 ± 1.5 mb at 7 TeV and 74.7 ± 1.7 mb at 8 TeV, show an increase of the cross-sections as a function of energy as expected. The inelastic cross-section at 7 TeV was also measured using an alternative method based on the CMS luminosity to determine the cross-section from the inelastic rate, with no measurement of the elastic part needed. The result 73.7 ± 3.4 mb is compatible with the luminosity independent measurement. The cross-section obtained requiring particles in the instrumented region |η|≤ 6.5 was 70.5 ± 2.9 mb. Using this and a measurement of the full inelastic cross-section based on elastic scattering, which contains no assumptions about low mass diffraction, an upper limit for low mass diffraction with all final state particles at |η|> 6.5 of ≤ 6.31 mb was obtained at 95 % confidence level. Likewise, the cross-sections of the individual inelastic processes, most importantly non-, single and double diffractive, cannot be calculated from first principles, but are of high importance for further improvements of the models and the modelling of cosmic air showers. They are difficult to measure since the differences in the experimental signatures between different processes can be small, even identical, in some parts of the phase space. A good detector coverage is therefore essential and the cross-sections are most efficiently determined from the data with the use of a multivariate analysis method in order to exploit even small differences between the processes. The majority of diffractive events have a clear rapidity gap and hence an experimental definition, where diffractive events were defined as having a rapidity gap of at least three units, was used in order to avoid a model-dependent definition of diffraction. If the event had a proton at minimum or maximum pseudorapidity followed by a rapidity gap of at least three units, it was considered single diffractive, other events with such a gap double diffractive and the remaining events non-diffractive. The cross-sections obtained using a classifier based on boosted decision trees, on data recorded with the combined CMS and TOTEM detectors at 8 TeV center of mass collision energy, were 50.0 ± 2.2 mb for non-diffractive, 16.0 ± 3.5 mb for single diffractive and 8.7 ± 0.9 mb for double diffractive. These results are in agreement with other measurements using the same definitions and indicate larger diffractive cross-sections than predicted by most models.Alkeishiukkasfysiikka tutkii maailmankaikkeuden kaikkein pienimpiä hiukkasia. Hiukkasten vuorovaikutuksia ja ominaisuuksia tutkitaan törmäyttämällä hiukkasia suurella energialla, jolloin on mahdollista, että hiukkaset hajoavat tai vuorovaikuttavat muodostaen uuden joukon hiukkasia. Mittauksista saatavia tuloksia hyödynnetään muun muassa alkeishiukkasfysiikan ja astrohiukkasfysiikan mallien kehittämisessä. Tässä työssä tutkittiin CERNin Large Hadron Collider -kiihdyttimellä tuotettua dataa kahden protonin törmäyksistä. Mittausten tavoitteena oli määrittää erinäisiä kahden protonin törmäyksen vaikutusaloja, eli tutkittavien vuorovaikutusten todennäköisyyksiä. Nämä vaikutusalat eivät ole vakioita, vaan riippuvat törmäysenergiasta. Ensinnäkin tutkittiin epäelastista vaikutusalaa kolmella eri törmäysenergialla. Epäelastinen vaikutusala kuvaa todennäköisyyttä, että törmäyksessä muodostuu uusia hiukkasia alkuperäisten protonien lisäksi tai tilalle. Mittauksissa saavutettiin ennennäkemätön mittaustarkkuus ja havaittiin, että epäelastiset vaikutusalat kasvoivat energian kasvaessa, kuten mallit ennustivat. Mittausten hyvä tarkkuus tarjoaa hyvät mahdolliset kehittää olemassa olevia ja uusia malleja hiukkasten vuorovaikutuksille. Lisäksi tutkittiin epäelastisen vaikutusalan jakautumista eri vuorovaikutusmekanismien kesken. Suurimman osan epäelastisesta vaikutusalasta muodostavat ei-diffraktiivinen, yksöisdiffraktiivinen ja kaksoisdiffraktiivinen sironta. Ensimmäiseksi mainitussa törmäävät hiukkaset hajoavat ja uusia hiukkasia muodostuu tasaisesti eri sirontakulmiin. Toiseksi mainitussa yksi törmäävistä protoneista säilyy ennallaan ja toisen protonin hajotessa muodostuu joukko hiukkasia lähinnä sille puolelle törmäyspistettä, missä hajoava protoni sijaitsi. Kolmannessa tapauksessa molemmat protonit hajoavat, mutta uusia hiukkasia muodostuu törmäyspisteen molemmille puolille siten, että keskellä on hiukkasista vapaa alue. Epäelastisen vaikutusalan jakautumista eri vaikutusmekanismien kesken tutkittiin hyödyntämällä simulaatioita ja koneoppimismenetelmiä. Simuloitujen törmäystapahtumien avulla opetettiin päätöspuu tunnistamaan erilaisia törmäyksiä ja sitten hyödynnettiin kyseistä päätöspuuta mitattujen törmäysten luokitteluun. Näin saatiin määritettyä ei-diffraktiivisen, yksöisdiffraktiivisen ja kaksoisdiffraktiivisen sironnan osuudet. Mittauksissa huomattiin, että saadut tulokset ennustavat yksöis- ja kaksoisdiffaktion olevan olemassaolevien mallien ennusteita suuremmassa merkityksessä

Characterisation of the dip-bump structure observed in proton-proton elastic scattering at root s=8 TeV

We describe an analysis comparing the p (p) over bar elastic cross section as measured by the D0 Collaboration at a center-of-mass energy of 1.96 TeV to that in pp collisions as measured by the TOTEM Collaboration at 2.76, 7, 8, and 13 TeVusing a model-independent approach. The TOTEM cross sections, extrapolated to a center-of-mass energy of root s = 1.96 TeV, are compared with the D0 measurement in the region of the diffractive minimum and the second maximum of the pp cross section. The two data sets disagree at the 3.4s level and thus provide evidence for the t-channel exchange of a colorless, C-odd gluonic compound, also known as the odderon. We combine these results with a TOTEM analysis of the same C-odd exchange based on the total cross section and the ratio of the real to imaginary parts of the forward elastic strong interaction scattering amplitude in pp scattering for which the significance is between 3.4s and 4.6s. The combined significance is larger than 5 sigma and is interpreted as the first observation of the exchange of a colorless, C-odd gluonic compound.Peer reviewe

Odderon Exchange from Elastic Scattering Differences between pp and p(p)over-bar Data at 1.96 TeV and from pp Forward Scattering Measurements

We describe an analysis comparing the p (p) over bar elastic cross section as measured by the D0 Collaboration at a center-of-mass energy of 1.96 TeV to that in pp collisions as measured by the TOTEM Collaboration at 2.76, 7, 8, and 13 TeVusing a model-independent approach. The TOTEM cross sections, extrapolated to a center-of-mass energy of root s = 1.96 TeV, are compared with the D0 measurement in the region of the diffractive minimum and the second maximum of the pp cross section. The two data sets disagree at the 3.4s level and thus provide evidence for the t-channel exchange of a colorless, C-odd gluonic compound, also known as the odderon. We combine these results with a TOTEM analysis of the same C-odd exchange based on the total cross section and the ratio of the real to imaginary parts of the forward elastic strong interaction scattering amplitude in pp scattering for which the significance is between 3.4s and 4.6s. The combined significance is larger than 5 sigma and is interpreted as the first observation of the exchange of a colorless, C-odd gluonic compound.Peer reviewe

First Search for Exclusive Diphoton Production at High Mass with Tagged Protons in Proton-Proton Collisions at root s=13 TeV

A search for exclusive two-photon production via photon exchange in proton-proton collisions, pp -> p gamma gamma p with intact protons, is presented. The data correspond to an integrated luminosity of 9.4 fb(-1) collected in 2016 using the CMS and TOTEM detectors at a center-of-mass energy of 13 TeVat the LHC. Events are selected with a diphoton invariant mass above 350 GeVand with both protons intact in the final state, to reduce backgrounds from strong interactions. The events of interest are those where the invariant mass and rapidity calculated from the momentum losses of the forward-moving protons match the mass and rapidity of the central, two-photon system. No events are found that satisfy this condition. Interpreting this result in an effective dimension-8 extension of the standard model, the first limits are set on the two anomalous four-photon coupling parameters. If the other parameter is constrained to its standard model value, the limits at 95% confidence level are vertical bar zeta(1)vertical bar < 2.9 x 10(-1)3 GeV-4 and vertical bar zeta(2)vertical bar < 6.0 x 10(-13) GeV-4.Peer reviewe

Patatin-related phospholipase pPLAIIIδ increases seed oil content with long-chain fatty acids in Arabidopsis

The release of fatty acids from membrane lipids has been implicated in various metabolic and physiological processes, but in many cases, the enzymes involved and their functions in plants remain unclear. Patatin-related phospholipase As (pPLAs) constitute a major family of acyl-hydrolyzing enzymes in plants. Here, we show that pPLAIIIδ promotes the production of triacylglycerols with 20- and 22-carbon fatty acids in Arabidopsis (Arabidopsis thaliana). Of the four pPLAIIIs (α, β, γ, δ), only pPLAIIIδ gene knockout results in a decrease in seed oil content, and pPLAIIIδ is most highly expressed in developing embryos. The overexpression of pPLAIIIδ increases the content of triacylglycerol and 20- and 22-carbon fatty acids in seeds with a corresponding decrease in 18-carbon fatty acids. Several genes in the glycerolipid biosynthetic pathways are up-regulated in pPLAIIIδ-overexpressing siliques. pPLAIIIδ hydrolyzes phosphatidylcholine and also acyl-coenzyme A to release fatty acids. pPLAIIIδ-overexpressing plants have a lower level, whereas pPLAIIIδ knockout plants have a higher level, of acyl-coenzyme A than the wild type. Whereas seed yield decreases in transgenic plants that ubiquitously overexpress pPLAIIIδ, seed-specific overexpression of pPLAIIIδ increases seed oil content without any detrimental effect on overall seed yield. These results indicate that pPLAIIIδ-mediated phospholipid turnover plays a role in fatty acid remodeling and glycerolipid production

Oseltamivir-resistant influenza virus A (H1N1), Europe, 2007-08 season.

Contains fulltext : 81631.pdf (publisher's version ) (Open Access)In Europe, the 2007-08 winter season was dominated by influenza virus A (H1N1) circulation through week 7, followed by influenza B virus from week 8 onward. Oseltamivir-resistant influenza viruses A (H1N1) (ORVs) with H275Y mutation in the neuraminidase emerged independently of drug use. By country, the proportion of ORVs ranged from 0% to 68%, with the highest proportion in Norway. The average weighted prevalence of ORVs across Europe increased gradually over time, from near 0 in week 40 of 2007 to 56% in week 19 of 2008 (mean 20%). Neuraminidase genes of ORVs possessing the H275Y substitution formed a homogeneous subgroup closely related to, but distinguishable from, those of oseltamivir-sensitive influenza viruses A (H1N1). Minor variants of ORVs emerged independently, indicating multiclonal ORVs. Overall, the clinical effect of ORVs in Europe, measured by influenza-like illness or acute respiratory infection, was unremarkable and consistent with normal seasonal activity