Charmonium production measured in PbPb and pp collisions by CMS

The Compact Muon Solenoid (CMS) is fully equipped to measure hard probes in the di-muon decay channel in the high multiplicity environment of nucleus-nucleus collisions. Such probes are especially relevant for studying the quark-gluon plasma since they are produced at early times and propagate through the medium, mapping its evolution. CMS is able to distinguish non-prompt from prompt J/psi in pp and PbPb collisions. We report here the nuclear modification factor of prompt J/psi in PbPb as a function of transverse momentum, rapidity, and the number of nucleons participating in the collision.Comment: 4 pages, 4 figures. To appear in Proc. 22nd Int. Conf. on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2011), Annecy, France, May 23-28, 201

Quarkonia and heavy-flavour production in CMS

The Compact Muon Solenoid (CMS) has measured numerous quarkonium states via their decays into muon pairs in pp and PbPb collisions at sqrt(s_NN) = 2.76 TeV. Quarkonia are especially relevant for studying the quark-gluon plasma since they are produced at early times and propagate through the medium, mapping its evolution. Non-prompt J/psi from b-hadron decays show a strong suppression in the transverse momentum range (6.5 < p_T < 30 GeV/c) when compared to the yield in pp collisions scaled by the number of inelastic nucleon-nucleon collisions. This suppression is related to the in-medium b-quark energy loss. In the same kinematic region, for prompt J/psi, a strong, centrality-dependent suppression is observed in PbPb collisions. Such strong suppression at high p_T has previously not been observed at RHIC. At midrapidity (|y| < 1.6) and the same p_T region, inclusive psi(2S) are even stronger suppressed than J/psi, whereas psi(2S) at forward rapidity (1.6 < |y| < 2.4) and lower p_T (3 < p_T < 30 GeV/c) appear to be less suppressed than J/psi, however, with large uncertainties that prevent a conclusion. Furthermore, low-p_T Y(2S) and Y(3S) mesons are strongly suppressed in PbPb collisions. The suppression of the Y(1S) state is smaller than the suppression of the excited states and consistent with the suppression of the feed-down contribution only.Comment: 10 pages, 5 figures. To appear in Proc. 5th Int. Conf. on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions, Cagliari, Italy, May 27-June 1, 2012; (v2: fixed typos

Measurement of the dielectron continuum in p+p and Au+Au collisions at RHIC

PHENIX has measured the e^+e^- pair continuum in sqrt(s_NN) = 200 GeV Au+Au and p+p collisions over a wide range of mass and transverse momenta. While the p+p data in the mass range below the phi meson are well described by known contributions from light meson decays, the Au+Au minimum bias inclusive mass spectrum shows an enhancement by a factor of 4.7 +/- 0.4(stat)} +/- 1.5(syst) +/- 0.9(model) in the mass range 0.15<m_ee<0.75 GeV/c^2. At low mass (m_ee<0.3 GeV/c^2) and high p_T (1<p_T<5~GeV/c) an enhanced e^+e^- pair yield is observed that is in qualitative agreement with hydrodynamical models of thermal photon emission with initial temperatures ranging from T_init ~= 300-600 MeV at times of 0.6-0.15 fm/c after the collision.Comment: 6 pages, 4 figures. To appear in Proc. of XLVth Rencontres de Moriond 2010 - QCD and High Energy Interactions, La Thuile, Italy, March 13-20, 201

Upsilon suppression in PbPb collisions at the LHC

The Compact Muon Solenoid (CMS) has measured the suppression of the bottomonium states Y(1S), Y(2S), and Y(3S) in PbPb collisions at sqrt(s_NN) = 2.76 TeV relative to pp collisions, scaled by the number of inelastic nucleon-nucleon collisions. CMS observed a stronger suppression for the weaker bound Y(2S) and Y(3S) states than for the ground state Y(1S). Such "sequential melting" has been predicted to be a clear signature for the creation of a quark-gluon plasma. The suppression of the Y(1S) and Y(2S) has been measured as a function of collision centrality for Y in the rapidity interval |y| < 2.4 and with transverse momentum (p_T) down to 0. Furthermore, the p_T and rapidity dependence of the Y(1S) suppression are presented.Comment: 7 pages, 3 figures. To appear in Proc. 14th Int. Conf. on B-Physics at Hadron Machines (Beauty 2013), Bologna, Italy, April 8-12, 201

Optimisation of simultaneous train formation and car sorting at marshalling yards

Efficient and correct freight train marshalling is vital for high quality carload freight transportations. During marshalling, it is desirable that cars are sorted according to their individual drop-off locations in the outbound freight trains. Furthermore, practical limitations such as non-uniform and limited track lengths and the arrival and departure times of trains need to be considered. This paper presents a novel optimisation method for freight marshalling scheduling under these circumstances. The method is based on an integer programming formulation that is solved using column generation and branch and price. The approach minimises the number of extra shunting operations that have to be performed, and is evaluated on real-world data from the Hallsberg marshalling yard in Sweden

Quarkonium studies in p+p and Pb+Pb collisions with CMS

The collisions of Pb nuclei at the LHC will create strongly interacting matter at unprecedented energy densities, allowing us to probe QCD at extreme temperatures and very low parton momentum fractions. This paper presents the capabilities of the CMS experiment to study the production of quarkonium states in $p+p$ and Pb+Pb collisions. The very good acceptance and excellent dimuon mass resolution will allow us to do with the three $\Upsilon$ states (1S, 2S, 3S) the exciting measurements previously performed with the $J/\psi$ and $\psi'$ states, at the SPS and RHIC

Optimized shunting with mixed-usage tracks

We consider the planning of railway freight classification at hump yards, where the problem involves the formation of departing freight train blocks from arriving trains subject to scheduling and capacity constraints. The hump yard layout considered consists of arrival tracks of sufficient length at an arrival yard, a hump, classification tracks of non-uniform and possibly non-sufficient length at a classification yard, and departure tracks of sufficient length. To increase yard capacity, freight cars arriving early can be stored temporarily on specific mixed-usage tracks. The entire hump yard planning process is covered in this paper, and heuristics for arrival and departure track assignment, as well as hump scheduling, have been included to provide the neccessary input data. However, the central problem considered is the classification track allocation problem. This problem has previously been modeled using direct mixed integer programming models, but this approach did not yield lower bounds of sufficient quality to prove optimality. Later attempts focused on a column generation approach based on branch-and-price that could solve problem instances of industrial size. Building upon the column generation approach we introduce a direct arc-based integer programming model, where the arcs are precedence relations between blocks on the same classification track. Further, the most promising models are adapted for rolling-horizon planning. We evaluate the methods on historical data from the Hallsberg shunting yard in Sweden. The results show that the new arc-based model performs as well as the column generation approach. It returns an optimal schedule within the execution time limit for all instances but from one, and executes as fast as the column generation approach. Further, the short execution times of the column generation approach and the arc-indexed model make them suitable for rolling-horizon planning, while the direct mixed integer program proved to be too slow for this. Extended analysis of the results shows that mixing was only required if the maximum number of concurrent trains on the classification yard exceeds 29 (there are 32 available tracks), and that after this point the number of extra car roll-ins increases heavily

Linear Stochastic Reserving Methods

In this article we want to motivate and analyse a wide family of reserving models, called linear stochastic reserving methods (LSRMs). The main idea behind them is the assumption that the (conditionally) expected changes of claim properties during a development period are proportional to exposures which depend linearly on the past. This means the discussion about the choice of reserving methods can be based on heuristic reasons about exposures driving the claims development, which in our opinion is much better than a pure philosophic approach. Moreover, the assumptions of LSRMs do not include the independence of accident periods. We will see that many common reserving methods, like the Chain-Ladder-Method, the Bornhuetter-Ferguson-Method and the Complementary-Loss-Ratio-Method, can be interpreted in this way. But using the LSRM framework you can do more. For instance you can couple different triangles via exposures. This leads to reserving methods which look at a whole bundle of triangles at once and use the information of all triangles in order to estimate the future development of each of them. We will present unbiased estimators for the expected ultimate and estimators for the mean squared error of prediction, which may become an integral part of IFRS 4. Moreover, we will look at the one period solvency reserving risk, which already is an important part of Solvency II, and present a corresponding estimator. Finally we will present two examples that illustrate some features of LSRM

The influence of competences and institutions on the international market orientation in foreign-owned subsidiaries

The international market orientation of foreign-owned subsidiaries, defined here as the importance of markets supplied outside their host country, can and often does, plays a vital role for managers as well as policy makers. This paper investigates how multilevel corporate competences and institutional differences stand to influence international market orientation and performance among firms. Our research is based on a survey of subsidiaries located in the mid-range, emerging economy of Taiwan. The results are analysed using SEM-PLS method. We found that competences that emerge from the subsidiary itself and competences from multinational enterprise networks serve to enhance; whereas, competences emerging from headquarters’ operations can have an adverse effect on international market orientation. Institutional differences add to the overall complexity through direct and moderating effects. This study indicates that the competence-based view of the firm can be enriched with insights from institutional theory in order to expand our understanding of subsidiary development located in emerging economies and also with their international market orientation in particular