CERN Document Server: CERN Series
https://cds.cern.ch/collection/CERN%20Series
CERN Document Server latest documents in CERN SeriesenFri, 06 Mar 2015 07:22:13 GMTInvenio 1.1.3.1106-62468cds.support@cern.ch36021740125https://cds.cern.ch/img/site_logo_rss.pngCERN Document Server
https://cds.cern.ch
Search Search this site:p
https://cds.cern.ch/search
Froissart Bound on Inelastic Cross Section Without Unknown Constants
https://cds.cern.ch/record/1997117
Assuming that axiomatic local field theory results hold for hadron scattering, Andr\'e Martin and S. M. Roy recently obtained absolute bounds on the D-wave below threshold for pion-pion scattering and thereby determined the scale of the logarithm in the Froissart bound on total cross sections in terms of pion mass only. Previously, Martin proved a rigorous upper bound on the inelastic cross-section $\sigma_{inel}$ which is one-fourth of the corresponding upper bound on $\sigma_{tot}$, and Wu, Martin,Roy and Singh improved the bound by adding the constraint of a given $\sigma_{tot}$. Here we use unitarity and analyticity to determine, without any high energy approximation, upper bounds on energy averaged inelastic cross sections in terms of low energy data in the crossed channel. These are Froissart-type bounds without any unknown coefficient or unknown scale factors and can be tested experimentally. Alternatively, their asymptotic forms,together with the Martin-Roy absolute bounds on pion-pion D-waves below threshold, yield absolute bounds on energy-averaged inelastic cross sections. E.g. for $\pi^0 \pi^0$ scattering, defining $\sigma_{inel}=\sigma_{tot} -\big (\sigma^{\pi^0 \pi^0 \rightarrow \pi^0 \pi^0} + \sigma^{\pi^0 \pi^0 \rightarrow \pi^+ \pi^-} \big )$,we show that for c.m. energy $\sqrt{s}\rightarrow \infty $, $\bar{\sigma}_{inel }(s,\infty)\equiv s\int_{s} ^{\infty } ds'\sigma_{inel }(s')/s'^2 \leq (\pi /4) (m_{\pi })^{-2} [\ln (s/s_1)+(1/2)\ln \ln (s/s_1) +1]^2$ where $1/s_1= 34\pi \sqrt{2\pi }\>m_{\pi }^{-2} $ . This bound is asymptotically one-fourth of the corresponding Martin-Roy bound on the total cross section, and the scale factor $s_1$ is one-fourth of the scale factor in the total cross section bound. The average over the interval (s,2s) of the inelastic $\pi^0 \pi^0 $cross section has a bound of the same form with $1/s_1$ replaced by $1/s_2=2/s_1 $.Martin, AndréThu, 05 Mar 2015 07:11:16 GMThttps://cds.cern.ch/record/1997117Gauge-invariant signatures of spontaneous gauge symmetry breaking by the Hosotani mechanism
https://cds.cern.ch/record/1996449
The Hosotani mechanism claims to achieve gauge-symmetry breaking, for instance $SU(3) \to SU(2)\times U(1)$. To verify this claim, we propose to monitor the stability of a topological defect stable under a gauge subgroup but not under the whole gauge group, like a $U(1)$ flux state or monopole in the case above. We use gauge invariant operators to probe the presence of the topological defect to avoid any ambiguity introduced by gauge fixing. Our method also applies to an ordinary gauge-Higgs system.Akerlund, OscarWed, 04 Mar 2015 06:42:56 GMThttps://cds.cern.ch/record/1996449On jet substructure methods for signal jets
https://cds.cern.ch/record/1996443
We carry out simple analytical calculations and Monte Carlo studies to better understand the impact of QCD radiation on some well-known jet substructure methods for jets arising from the decay of boosted Higgs bosons. Understanding differences between taggers for these signal jets assumes particular significance in situations where they perform similarly on QCD background jets. As an explicit example of this we compare the Y-splitter method to the more recently proposed Y-pruning technique. We demonstrate how the insight we gain can be used to significantly improve the performance of Y-splitter by combining it with trimming and show that this combination outperforms the other taggers studied here, at high $p_T$. We also make analytical estimates for optimal parameter values, for a range of methods and compare to results from Monte Carlo studies.Dasgupta, MrinalWed, 04 Mar 2015 06:40:25 GMThttps://cds.cern.ch/record/1996443CERN contribution to the future neutrino programsCERN contribution to the future neutrino programs
https://cds.cern.ch/record/1995603
Bertolucci, SergioTue, 03 Mar 2015 13:58:44 GMThttps://cds.cern.ch/record/1995603Gala presentationsChallenge Based Innovation Gala - final presentations & prototype expo
https://cds.cern.ch/record/1995424
KURIKKA, Joona JuhaniMon, 02 Mar 2015 11:53:55 GMThttps://cds.cern.ch/record/1995424Universality of radiative corrections to gauge couplings for strings with spontaneously broken supersymmetry
https://cds.cern.ch/record/1995142
I review recent work on computing radiative corrections to non-abelian gauge couplings in four-dimensional heterotic vacua with spontaneously broken supersymmetry. The prototype models can be considered as K3 surfaces with additional Scherk-Schwarz fluxes inducing the spontaneous $\mathcal{N}=2 \to \mathcal{N}=0$ breaking. Remarkably, although the gauge thresholds are no longer BPS protected and receive contributions also from the excitations of the RNS sector, their difference is still exactly computable and universal. Based on a talk presented at the DISCRETE 2014 conference at King's College London.Florakis, IoannisSat, 28 Feb 2015 07:51:05 GMThttps://cds.cern.ch/record/1995142Cloud Machine LearningCloud Machine Learning
https://cds.cern.ch/record/1995036
Joseph Sirosh will talk about how the cloud is changing the picture for data
science and machine learning. Bringing the power of the cloud to machine
learning makes it possible to dramatically compress the time it takes to
develop and deploy analytics in production. With examples from various case
studies he will show how Azure Machine Learning, Microsoft's new product,
enables the use of the latest algorithms for big data, and how easily
scalable cloud APIs can be built and deployed to enable intelligence in any
connected application.
About the speaker
Joseph Sirosh is the corporate vice president of the Information Management
and Machine Learning (IMML) team in the Cloud and Enterprise group at
Microsoft Corp. Sirosh and his IMML team have delivered several innovative
advanced analytics services in the past year including Microsoft Azure
Machine Learning, Azure Stream Analytics and Azure Data Factory. His team is
also involved in the recent agreement by Microsoft to acquire Revolution
Analytics, the leading commercial provider of software and services for R,
the world's most widely used programming language for statistical computing
and predictive analytics. Sirosh joined Microsoft in fall 2013 from
Amazon.com Inc. where he was vice president for the Global Inventory
Platform and chief technology officer of the core retail business. Before
joining Amazon, he worked for Fair Isaac Corp. as vice president of research
and development. He is passionate about machine learning and its
applications and has been active in the field since 1990.
Sirosh, JosephFri, 27 Feb 2015 16:04:59 GMThttps://cds.cern.ch/record/1995036Fixed telephony evolution at CERNFixed telephony evolution at CERN
https://cds.cern.ch/record/1995032
The heart of CERN’s telephony infrastructure consists of the Alcatel IP-PBX that links CERN’s fixed line phones, Lync softphones and CERN’s GSM subscribers to low-cost local and international telephony services. The PABX infrastructure also supports the emergency “red telephones” in the LHC tunnel and provides vital services for the Fire and Rescue Service and the CERN Control Centre. Although still reliable, the Alcatel hardware is increasingly costly to maintain and looking increasingly outmoded in a market where open source solutions are increasingly dominant.
After presenting an overview of the Alcatel PABX and the services it provides, including innovative solutions such as the Closed User Group for our mobile telephony services, we present a possible architecture for a software based system designed to meet tomorrow’s communication needs and describe how the introduction of open-source call routers based on the SIP protocol and Session Border Controllers (SBC) could foster the introduction of new services and increase the agility of our telephony network to adapt to new communication standards.VALENTIN VINAGRERO, FranciscoFri, 27 Feb 2015 15:49:17 GMThttps://cds.cern.ch/record/1995032Infinitesimal diffeomorfisms on the latticeInfinitesimal diffeomorfisms on the lattice
https://cds.cern.ch/record/1994480
The energy-momentum tensor and local translation Ward identities constitute the essential toolkit to probe the response of a QFT to an infinitesimal change of geometry. This is relevant in a number of contexts. For instance in order to get the thermodynamical equation of state, one wants to study the response of a Euclidean QFT in a finite box to a change in the size of the box.
The lattice formulation of QFTs is a prime tool to study their dynamics beyond perturbation theory. However Poincaré invariance is explicitly broken, and is supposed to be recovered only in the continuum limit. Approximate local Ward identities for translations can be defined, by they require some care for two reasons: 1) the energy-momentum tensor needs to be properly defined through a renormalization procedure; 2) the action of infinitesimal local translations (i.e. infinitesimal diffeomorfisms) is ill-defined on local observables.
In this talk I will review the issues related to the renormalization of the energy-momentum tensor on the lattice. I will also show how it is possible to define properly the action of infinitesimal diffeomorfisms on a particular class of observables, i.e. non local observables defined through the gradient flow. I will present also possible numerical applications.Patella, AgostinoWed, 25 Feb 2015 16:01:48 GMThttps://cds.cern.ch/record/1994480Legal aspects of Joint Pre-Commercial Procurements: from modeling to implementationLegal aspects of Joint Pre-Commercial Procurements: from modeling to implementation
https://cds.cern.ch/record/1994476
The delivery of Information and Communication Technology (ICT) services is changing fundamentally. Cloud-based services are replacing traditional local - or on-premises - software and infrastructure installations for many public sector organisations. This applies to government but also to public research organisations, including libraries, which currently deal with the outburst of big data and the need for additional computing capacity. While technology service options continue to evolve, procurement processes and policies have remained firmly rooted in historical practices that are no longer effective. In order for public research organisations of all sizes to take advantage of the best solutions the market has to offer nowadays, a more flexible and agile procurement process must be created and implemented.
The objective of this presentation is to review strategies and tips in order to help procurers implement and publish a Joint Pre-Commercial Procurement tender; including:
General legal framework of PCPs
Joint PCPs minimum requirements and constraints
Pros and cons of different suitable procurement models
Lessons learned from Cloud for Europe and NYMPHA-MD
About the speaker
Francesca Cinardo holds a Master’s Degree in European and Transnational Law obtained at the University of Trento. During 2008/2009, she attended the Lancaster University’s Law School (UK). Her experiences include, among others, the collaboration with a Law firm specialized in civil law, and a biannual collaboration with an Associated Notary Public Office, where she increased legal competences in corporate law. Since July 2013, she is working as Legal Advisor at Trento RISE. Her activity focuses on giving horizontal legal support to EU co-funded Joint PCP projects (i.e. Cloud for Europe and NYMPHA-MD). She is involved in drafting agreements regulating the contractual relationship between groups of public purchasers and between public purchasers and contractors. Her activity consists also in drafting contracts for the execution of other European projects addressed South-East Europe.
About Trento RISE
Trento RISE is a new ICT pole of excellence with expertise in Pre-Commercial Procurement (PCP) procedures, which contributes to the implementation of two Joint PCP projects co-funded by the European Union, Cloud for Europe and NYMPHA-MD, respectively in the Cloud Computing and e-health fields. Its contribution concerns the legal coordination of PCPs, which implies drafting Joint Pre-Commercial Procurement processes (e.g. the Tender documentation) and horizontal legal support; from the adoption of a suitable model between the public procurers to the implementation of PCP.
Cinardo, FrancescaWed, 25 Feb 2015 15:39:05 GMThttps://cds.cern.ch/record/1994476Superconductivity and its applications for societySuperconductivity and its applications for society
https://cds.cern.ch/record/1994296
High-energy physics has been a major driving force in the development of applied superconductivity, the two fields becoming an example of exceptional merging between fundamental physics research and technological development. The discovery of High Temperature Superconductivity has generated great enthusiasm in a new class of materials that could enlarge the variety of applications. These materials could offer solutions to fundamental challenges of the 21st century, in particular the storage of energy and distribution of electric power.
The talk discusses superconductivity and its potential applications that could transform our economy and daily life.
Dr. Ballarino, AmaliaWed, 25 Feb 2015 09:44:17 GMThttps://cds.cern.ch/record/1994296Director General of UNOG presents the UN world and the relations with CERNDirector General of UNOG presents the UN world and the relations with CERN
https://cds.cern.ch/record/1994260
This is the first of a series of lectures for CERN people given by Heads of international Organizations with which CERN has Co-operation Agreements. The seminars feature a presentation followed by a Q&A; session.Dr. Møller, MichaelWed, 25 Feb 2015 06:49:32 GMThttps://cds.cern.ch/record/1994260Emerging Jets
https://cds.cern.ch/record/1993313
In this work, we propose a novel search strategy for new physics at the LHC that utilizes calorimeter jets that (i) are composed dominantly of displaced tracks and (ii) have many different vertices within the jet cone. Such emerging jet signatures are smoking guns for models with a composite dark sector where a parton shower in the dark sector is followed by displaced decays of dark pions back to SM jets. No current LHC searches are sensitive to this type of phenomenology. We perform a detailed simulation for a benchmark signal with two regular and two emerging jets, and present and implement strategies to suppress QCD backgrounds by up to six orders of magnitude. At the 14 TeV LHC, this signature can be probed with mediator masses as large as 1.5 TeV for a range of dark pion lifetimes, and the reach is increased further at the high-luminosity LHC. The emerging jet search is also sensitive to a broad class of long-lived phenomena, and we show this for a supersymmetric model with R-parity violation. Possibilities for discovery at LHCb are also discussed.Schwaller, PedroFri, 20 Feb 2015 08:33:38 GMThttps://cds.cern.ch/record/1993313Exploring the Hidden Sector @ Low EnergiesExploring the Hidden Sector @ Low Energies
https://cds.cern.ch/record/1993061
Over the years we have accumulated a large number of indications for physics beyond the standard model. This new physics is often sought-after at high masses and energies. Here collider experiments can bring decisive insights. However, over recent years it has become increasingly clear that new physics can also appear at low energy, but extremely weak coupling. Experiments and observations at this `low energy frontier' therefore provide a powerful tool to gain insight into fundamental physics, which is complementary to accelerators. Prof. Jaeckel, JoergThu, 19 Feb 2015 06:55:07 GMThttps://cds.cern.ch/record/1993061Towards the physical point hadronic vacuum polarisation from Moebius DWF
https://cds.cern.ch/record/1992983
We present steps towards the computation of the leading-order hadronic contribution to the muon anomalous magnetic moment on RBC/UKQCD physical point DWF ensembles. We discuss several methods for controlling and reducing uncertainties associated to the determination of the HVP form factor.Marinkovic, MarinaThu, 19 Feb 2015 06:53:17 GMThttps://cds.cern.ch/record/1992983Muon Combined Performance reportATLAS Week - Ready for Data?
https://cds.cern.ch/record/1992887
BELLOMO, MassimilianoWed, 18 Feb 2015 15:06:07 GMThttps://cds.cern.ch/record/1992887Bottomonium production in p-Pb and Pb-Pb collisions in ALICEBottomonium production in p-Pb and Pb-Pb collisions in ALICE
https://cds.cern.ch/record/1992828
Quarkonium measurements play a crucial role in the investigation of the properties of the deconfined state of nuclear matter, the Quark-Gluon Plasma (QGP), produced in ultra-relativistic heavy ion collisions. In particular, the sequential suppression of the quarkonium states by colour screening has long been suggested as a signature and thermometer of the QGP.
The first results on charmonium suppression in Pb-Pb collisions at the LHC seem to indicate that, in addition to suppression mechanisms, a regeneration mechanism also plays a role. For bottomonia, such regeneration mechanism is expected to be small due to the smaller number of initial b-bbar pairs compared to c-cbar pairs. Initial state effects can also modify bottomonium production in Pb-Pb collisions. Initial state effects or Cold Nuclear Matter effects can be studied using proton-nucleus collisions, where no deconfined medium is expected to be created.
We will present the final results from Run1 on bottomonium production in p-Pb and Pb-Pb collisions measured with the ALICE muon spectrometer at forward-rapidity. The results will be compared to theoretical models and to other experimental results at LHC.
Castillo Castellanos, JavierWed, 18 Feb 2015 06:45:36 GMThttps://cds.cern.ch/record/1992828Fundamental Composite Electroweak Dynamics: Status at the LHC
https://cds.cern.ch/record/1992768
We determine the current status of the fundamental composite electroweak dynamics paradigm after the discovery of the Higgs boson at the Large Hadron Collider experiments. Our analysis serves as universal and minimal template for a wide class of models with the two limits in parameter space being composite Goldstone Higgs models and Technicolor. This is possible because of the existence of a unified description, both at the effective and fundamental Lagrangian levels, of models of composite Higgs dynamics where the Higgs boson itself can emerge, depending on the way the electroweak symmetry is embedded, either as a pseudo-Goldstone boson or as a massive excitation of the condensate. We constrain the available parameter space at the effective Lagrangian level. We show that a wide class of models of fundamental composite electroweak dynamics, including Technicolor, are compatible with experiments. The results are relevant for future searches of a fundamental composite nature of the Higgs mechanism at the Large Hadron Collider.Arbey, AlexandreWed, 18 Feb 2015 06:43:44 GMThttps://cds.cern.ch/record/1992768Robust collider limits on heavy-mediator Dark Matter
https://cds.cern.ch/record/1992767
We discuss how to consistently use Effective Field Theories (EFTs) to set universal bounds on heavy-mediator Dark Matter at colliders, without prejudice on the model underlying a given effective interaction. We illustrate the method for a Majorana fermion, universally coupled to the Standard Model quarks via a dimension-6 axial-axial four-fermion operator. We recast the ATLAS mono-jet analysis and show that a considerable fraction of the parameter space, seemingly excluded by a na\"ive EFT interpretation, is actually still unexplored. Consistently set EFT limits can be reinterpreted in any specific underlying model. We provide two explicit examples for the chosen operator and compare the reach of our model-independent method with that obtainable by dedicated analyses.Racco, DavideWed, 18 Feb 2015 06:43:42 GMThttps://cds.cern.ch/record/1992767Black Hole Solutions in $R^2$ Gravity
https://cds.cern.ch/record/1992512
We find static spherically symmetric solutions of scale invariant $R^2$ gravity. The latter has been shown to be equivalent to General Relativity with a positive cosmological constant and a scalar mode. Therefore, one expects that solutions of the $R^2$ theory will be identical to that of Einstein theory. Indeed, we find that the solutions of $R^2$ gravity are in one-to-one correspondence with solutions of General Relativity in the case of non-vanishing Ricci scalar. However, scalar-flat $R=0$ solutions are global minima of the $R^2$ action and they cannot in general be mapped to solutions of the Einstein theory. As we will discuss, the $R=0$ solutions arise in Einstein gravity as solutions in the tensionless, strong coupling limit $M_P\rightarrow 0$. As a further result, there is no corresponding Birkhoff theorem and the Schwarzschild black hole is by no means unique in this framework. In fact, $R^2$ gravity has a rich structure of vacuum static spherically symmetric solutions partially uncovered here. We also find charged static spherically symmetric backgrounds coupled to a $U(1)$ field. Finally, we provide the entropy and energy formulas for the $R^2$ theory and we find that entropy and energy vanish for scalar-flat backgrounds.Kehagias, AlexTue, 17 Feb 2015 06:33:49 GMThttps://cds.cern.ch/record/1992512$D^6 R^4$ amplitudes in various dimensions
https://cds.cern.ch/record/1989347
Four-graviton couplings in the low energy effective action of type II string vacua compactified on tori are strongly constrained by supersymmetry and U-duality. While the $R^4$ and $D^4 R^4$ couplings are known exactly in terms of Langlands-Eisenstein series of the U-duality group, the $D^6 R^4$ couplings are not nearly as well understood. Exploiting the coincidence of the U-duality group in $D=6$ with the T-duality group in $D=5$, we propose an exact formula for the $D^6 R^4$ couplings in type II string theory compactified on $T^4$, in terms of a genus-two modular integral plus a suitable Eisenstein series. The same modular integral computes the two-loop correction to $D^6 R^4$ in 5 dimensions, but here provides the non-perturbative completion of the known perturbative terms in $D=6$. This proposal hinges on a systematic re-analysis of the weak coupling and large radius of the $D^6 R^4$ in all dimensions $D\geq 3$, which fills in some gaps and resolves some inconsistencies in earlier studies.Pioline, BorisFri, 13 Feb 2015 06:37:29 GMThttps://cds.cern.ch/record/1989347Non-minimally flavour violating dark matter
https://cds.cern.ch/record/1989328
Flavour symmetries provide an appealing mechanism to stabilize the dark matter particle. I present a simple model of quark flavoured dark matter that goes beyond the framework of minimal flavour violation. I discuss the phenomenological implications for direct and indirect dark matter detection experiments, high energy collider searches as well as flavour violating precision data.Blanke, MonikaFri, 13 Feb 2015 06:36:59 GMThttps://cds.cern.ch/record/1989328Large Data Visualization with Open-Source ToolsLarge Data Visualization with Open-Source Tools
https://cds.cern.ch/record/1988107
Visualization and post-processing of large data have become increasingly challenging and require more and more tools to support the diversity of data to process. In this seminar, we will present a suite of open-source tools supported and developed by Kitware to perform large-scale data visualization and analysis. In particular, we will present ParaView, an open-source tool for parallel visualization of massive datasets, the Visualization Toolkit (VTK), an open-source toolkit for scientific visualization, and Tangelohub, a suite of tools for large data analytics.
About the speaker
Julien Jomier is directing Kitware's European subsidiary in Lyon, France, where he focuses on European business development. Julien works on a variety of projects in the areas of parallel and distributed computing, mobile computing, image processing, and visualization. He is one of the developers of the Insight Toolkit (ITK), the Visualization Toolkit (VTK), and ParaView. Julien is also leading the CDash project, an open-source continuous integration tool companion for CMake.
Jomier, JulienTue, 10 Feb 2015 15:26:38 GMThttps://cds.cern.ch/record/1988107Latest results on b-hadron spectroscopy at LHCbLatest results on b-hadron spectroscopy at LHCb
https://cds.cern.ch/record/1988103
Hadrons are systems bound by the strong interaction, which is described at the fundamental level by Quantum Chromodynamics (QCD). While QCD is well understood at high energy in the perturbative regime, low-energy phenomena such as the binding of quarks and gluons within hadrons are more difficult to predict. High precision measurements are most useful to test the reliability of several models and techniques, such as constituent-quark models or lattice-QCD calculations, into predicting the mass spectrum and the properties of the hadrons.
Using 3.0/fb of integrated luminosity recorded by the LHCb experiment, we report precise measurements of the B1(5721){0,+} and B2*(5747){0,+} states and the observation of B{+,0} pi{-,+} mass structures. The observations of two new Xib baryons are presented as well.
Pappagallo, MarcoTue, 10 Feb 2015 15:06:05 GMThttps://cds.cern.ch/record/1988103Generalized Metric Formulation of Double Field Theory on Group Manifolds
https://cds.cern.ch/record/1987944
We rewrite the recently derived cubic action of Double Field Theory on group manifolds [arXiv:1410.6374] in terms of a generalized metric and extrapolate it to all orders in the fields. For the resulting action, we derive the field equations and state them in terms of a generalized curvature scalar and a generalized Ricci tensor. Compared to the generalized metric formulation of DFT derived from tori, all these quantities receive additional contributions related to the non-trivial background. It is shown that the action is invariant under its generalized diffeomorphisms and 2D-diffeomorphisms. Imposing additional constraints relating the background and fluctuations around it, the precise relation between the proposed generalized metric formulation of DFT${}_\mathrm{WZW}$ and of original DFT from tori is clarified. Furthermore we show how to relate DFT${}_\mathrm{WZW}$ of the WZW background with the flux formulation of original DFT.Blumenhagen, RalphTue, 10 Feb 2015 07:07:43 GMThttps://cds.cern.ch/record/1987944