Pp Data Research Articles

Twist-3 fragmentation functions in a spectator model with gluon rescattering

We study the twist-3 fragmentation functions H and H˜, by applying a spectator model. In the calculation we consider the effect of the gluon rescattering at one loop level. We find that in this case the hard-vertex diagram, which gives zero contribution to the Collins function, does contribute to the fragmentation function H. The calculation shows that the twist-3 T-odd fragmentation functions are free of light-cone divergences. The parameters of the model are fitted from the known parametrization of the unpolarized fragmentation D1 and the Collins function H1⊥. We find that our result for the favored fragmentation function is consistent with the recent extraction on H and H˜ from pp data. We also check numerically the equation of motion relation for H, H˜ and find that relation holds fairly well in the spectator model.

The Potential of Participedia as a Crowdsourcing Tool for Comparative Analysis of Democratic Innovations

Participedia (PP; www.participedia.net) is an open global knowledge platform for researchers and practitioners in the field of democratic innovation and public engagement. It represents an experiment with a new and potentially powerful way to conduct social science research: crowdsourcing data on participatory processes from researchers and practitioners from all over the world and making that data freely available for analysis. This article reflects on the potential of PP to realize its long‐term aim of answering the basic research questions: what kinds of participatory processes work best, for what purposes, and under what conditions? Initially the article reviews the data model that informs PP and the types of comparative analysis it might enable. Our analysis draws on the PP data to explore the relationship between aspects of institutional design (including facilitation, forms of interaction, and decision methods) across a range of democratic innovations represented on the platform. The study offers important insights on institutional design, but also on the potential for crowdsourcing data from disparate communities.

Study of Z boson production in pp, pPb and PbPb collisions in CMS

The Z boson production is studied in PbPb and pp collisions at = 2.76 TeV and in pPbcollisions at = 5.02 TeV using data collected by the CMS experiment at the LHC. The Z boson production is observed to be proportional to the number of elementary nucleon-nucleon collisions in both PbPb and pPb collisions. The measured differential cross sections as a function of transverse momentum and rapidity are in agreement with NLO pQCD calculations using different parton distribution functions with and without nuclear effects. Using the PbPb and pp data, the nuclear modification factor is presented as well as the forward- backward ratio measured in pPb collisions.

Jet Measurements in Heavy-ion Collisions with CMS

The production of a strongly interacting medium in heavy-ion collisions is identified through suppression of high transverse momentum jets leading to an effect known as jet quenching. Detailed measurements of nuclear modification factors and energy flow of the aforementioned quenched jets are performed with the CMS detector. These new results extend previous measurements to large angles with respect to the quenched jets and increase reach in the transverse momentum range. High statistics pp, pPb and PbPb data taken in 2011-13 are used in the following analysis. A new data-driven method to estimate the underlying event contribution from the forward calorimeter energy distribution is employed which takes into account possible event by event flow modulation. The flavor dependence of energy loss of jets is studied by tagging heavy flavor b-jets in these systems.

Ultimate use of prestack seismic data: Integration of rock physics, amplitude-preserved processing, and elastic inversion

Elastic information carries important data about subsurface lithology and fluid. It is highly valued by the seismic exploration industry. Compared with other methodologies (e.g., 9C VSP and 3D 3C), prestack P-wave methods are used extensively to address reservoir and fluid prediction because of their wide availability of data. However, many traditional technologies can hardly extract accurate P-wave and S-wave information from conventional prestack PP data because of lacking systematic studies on how to properly handle prestack amplitudes. A new concept, prestack elastic integration (PEI), emphasizes comprehensive interactions among rock physics, amplitude-preserved processing, and inversion algorithm. The influences of the three aspects are examined and discussed with real examples. Moreover, achievements of PEI are demonstrated through its application on a complex lithologic reservoir in eastern China, in which PEI characterizes target reservoir properties much better than traditional methods do.

Study of Z production in PbPb and pp collisions at s N N = 2.76 $$ \sqrt{s_{\mathrm{NN}}}=2.76 $$ TeV in the dimuon and dielectron decay channels

The production of Z bosons is studied in the dimuon and dielectron decay channels in PbPb and pp collisions at sqrt(s[NN]) = 2.76 TeV, using data collected by the CMS experiment at the LHC. The PbPb data sample corresponds to an integrated luminosity of about 150 inverse microbarns, while the pp data sample collected in 2013 at the same nucleon-nucleon centre-of-mass energy has an integrated luminosity of 5.4 inverse picobarns. The Z boson yield is measured as a function of rapidity, transverse momentum, and collision centrality. The ratio of PbPb to pp yields, scaled by the number of inelastic nucleon-nucleon collisions, is found to be 1.06 +/- 0.05 (stat) +/- 0.08 (syst) in the dimuon channel and 1.02 +/- 0.08 (stat) +/- 0.15 (syst) in the dielectron channel, for centrality-integrated Z boson production. This binary collision scaling is seen to hold in the entire kinematic region studied, as expected for a colourless probe that is unaffected by the hot and dense QCD medium produced in heavy ion collisions.

Performance of the CMS missing transverse momentum reconstruction in pp data at √s = 8 TeV

The performance of missing transverse energy reconstruction algorithms is presented using √s=8 TeV proton-proton (pp) data collected with the CMS detector. Events with anomalous missing transverse energy are studied, and the performance of algorithms used to identify and remove these events is presented. The scale and resolution for missing transverse energy, including the effects of multiple pp interactions (pileup), are measured using events with an identified Z boson or isolated photon, and are found to be well described by the simulation. Novel missing transverse energy reconstruction algorithms developed specifically to mitigate the effects of large numbers of pileup interactions on the missing transverse energy resolution are presented. These algorithms significantly reduce the dependence of the missing transverse energy resolution on pileup interactions. Finally, an algorithm that provides an estimate of the significance of the missing transverse energy is presented, which is used to estimate the compatibility of the reconstructed missing transverse energy with a zero nominal value.

Scaling of charged particle production and centrality determination in p-Pb collisions at √sNN= 5.02 TeV at ALICE

Proton-nucleus collisions are studied in order to disentangle initial state effects, already present in cold nuclear matter, from final state effects, that are associated to the hot and strongly interacting medium created in A-A collisions. However, after the 2013 p-Pb data taking at LHC, the importance of p-A collisions on their own has been acknowledged. Several measurements clearly showed that p-A collisions cannot simply be explained by an incoherent superposition of proton-nucleon collisions, but indicate the presence of coherent and collective effects, with a strong dependence on the collision geometry. These measurements pointed out the need for a detailed characterization of the collision geometry.Typically, parameters such as the number of binary collisions N coll or the number of participating nucleons N part are used to characterize the centrality. In nucleus-nucleus interactions the centrality is usually estimated by measuring the charged particle multiplicity. However, in contrast to A-A, in p-A collisions the large fluctuations in a much reduced multiplicity environment generate a dynamical bias in centrality classes based on particle multiplicity measurement.The centrality determination is critically addressed and a different approach to extract the average N coll values, needed to compare p-A to pp data, is presented. The centrality dependence of primary charged-particle production and of transverse momentum distributions in p-A collisions at √s NN = 5.02 TeV measured by ALICE are presented.

Azimuthal amplitude variation with offset analysis of physical modeling data acquired over an azimuthally anisotropic medium

We evaluated a quantitative amplitude analysis of 3D physical model reflection data acquired over an experimental phenolic layer that modeled a fractured medium with one set of vertical fractures. The phenolic layer was overlain by two isotropic layers, the uppermost being water, and the data acquisition was designed to avoid the interference of the primary and ghost events. The elastic stiffness coefficients and hence the anisotropy of the phenolic layer were known in advance from a previous traveltime analysis. The reflection amplitudes from the top of the phenolic layer required corrections to make them suitable for an amplitude study. In addition to the usual amplitude corrections applied to seismic field data, a directivity correction specific to the physical model transducers was applied. The corrected amplitudes along different azimuths showed a clear azimuthal variation caused by the phenolic layer and agreed with amplitudes predicted theoretically. An amplitude variation with angle and azimuth inversion was performed for horizontal transverse isotropy (HTI) parameters of the phenolic layer. We determined from the inversion results that from the azimuthally varying P-wave reflectivity response, it was possible to estimate HTI parameters that compared favorably to those obtained previously by a traveltime analysis. This result made it possible to compute the S-wave splitting parameter [Formula: see text] (historically determined from S-wave data and directly related to fracture density) from a quantitative analysis of the PP data.

Measurement of prompt ψ(2S) to J/ψ yield ratios in Pb-Pb and p-p collisions at sqrt[sNN]=2.76 TeV.

The ratio between the prompt ψ(2S) and J/ψ yields, reconstructed via their decays into μ+ μ-, is measured in Pb-Pb and p-p collisions at sqrt[sNN]=2.76 TeV. The analysis is based on Pb-Pb and p-p data samples collected by CMS at the Large Hadron Collider, corresponding to integrated luminosities of 150 μb(-1) and 5.4 pb(-1), respectively. The double ratio of measured yields (Nψ(2S)/N(J/ψ))(Pb-Pb)/(Nψ(2S)/N(J/ψ))(p-p) is computed in three Pb-Pb collision centrality bins and two kinematic ranges: one at midrapidity, |y|<1.6, covering the transverse momentum range 6.5<pT<30 GeV/c, and the other at forward rapidity, 1.6<|y|<2.4, extending to lower pT values, 3<pT<30 GeV/c. The centrality-integrated double ratio changes from 0.45±0.13(stat)±0.07(syst) in the first range to 1.67±0.34(stat)±0.27(syst) in the second. This difference is most pronounced in the most central collisions.

Stochastic inversion of seismic PP and PS data for reservoir parameter estimation

We have investigated the value of isotropic seismic converted-wave (i.e., PS) data for reservoir parameter estimation using stochastic approaches based on a floating-grain rock-physics model. We first performed statistical analysis on a simple two-layer model built on actual borehole logs and compared the relative value of PS data versus amplitude-variation-with-offset (AVO) gradient data for estimating the floating-grain fraction. We found that PS data were significantly more informative than AVO gradient data in terms of likelihood functions, and the combination of PS and AVO gradient data together with PP data provided the maximal value for the reservoir parameter estimation. To evaluate the value of PS data under complex situations, we developed a hierarchical Bayesian model to combine seismic PP and PS data and their associated time registration. We extended a model-based Bayesian method developed previously for inverting seismic PP data only, by including PS responses and time registration as additional data and PS traveltime and reflectivity as additional variables. We applied the method to a synthetic six-layer model that closely mimics real field scenarios. We found that PS data provided more information than AVO gradient data for estimating the floating-grain fraction, porosity, net-to-gross, and layer thicknesses when their corresponding priors were weak.

Isolated photon measurements in pp and PbPb collisions with CMS

Abstract We report new measurements using isolated photons based on the high statistics 2.76 TeV pp reference data collected in 2013. The nuclear modification factors of reconstructed isolated photons, obtained by the comparison of heavy ion collisions and pp data, are presented and provide useful constraints to the nuclear parton distribution functions. For events containing a high p T isolated photon with an associated jet, the photon + jet p T imbalance is studied as a function of collision centrality and compared to pp data and model calculations. These measurements allow an unbiased characterization of the in-medium parton energy loss.

Measurements of b-jet nuclear modification factors in pPb and PbPb collisions with CMS

We present measurements of the nuclear modification factors RAA and RpA(PYTHIA) of b jets in lead-lead and proton-lead collisions, respectively, using the CMS detector. Jets from b-quark fragmentations are found by exploiting the long lifetime of the b-quark through tagging methods using distributions of the secondary vertex displacement. From these, b-jet cross-sections are calculated and compared to the pp cross-section from the 2.76 TeV pp data collected in 2013 and to a PYTHIA simulation at 5.02 TeV, where these center-of-mass energies correspond to those of the PbPb and pPb data. We observe significant suppression for b jets in PbPb, and a RpA(PYTHIA) value consistent with unity for b jets in pPb. Results from both collision species show remarkable correspondence with inclusive-jet suppression measurements, indicating that mass-dependent energy-loss effects are negligible at pT values greater than around 50 GeV/c. We use 150 inverse {\mu}b of lead-lead data and 35 inverse nb of proton-lead data collected at the LHC.

Measurements of charged particle spectra and nuclear modification factor in p+Pb collisions with the ATLAS detector

The ATLAS detector at the LHC obtained the sample of p+Pb data at $\sqrt{s_{NN}}={}$5.02TeV with integrated luminosity of 25nb${}^{-1}$, which can be compared to the pp data obtained by interpolating pp measurements at $\sqrt{s}={}$2.76TeV and 7TeV. Due to the excellent capabilities of the ATLAS detector, and its stable operation in heavy ion as well as proton-proton physics runs, the data allow measurements of the nuclear modification factor, ratio of heavy ion charged particle spectra divided by pp reference, in different centrality classes over a wide range of rapidity. The charged particle nuclear modification factor is found to vary significantly as a function of transverse momentum with a stronger dependence in more peripheral collisions.

Charmonia in pp and PbPb with CMS

The mechanisms through which charmonia production is modified in the high-density medium created in ultra-relativistic heavy-ion collisions are still not quantitatively understood. In order to disentangle different scenarios, a multi-dimensional analysis in a wide kinematic range is needed, in pp and AA collisions, looking at many observables that have different sensitivities to the various aspects of charmonia production. We will report on the prompt J / ψ measurements with the CMS detector, using the 150 μb − 1 of PbPb data recorded in 2011. The azimuthal anisotropy in PbPb collisions at 2.76 TeV will be presented. In addition, the comparison of the excited charmonium state ( ψ ( 2 S ) ) and the ground state ( J / ψ ) between PbPb and pp is updated, utilizing the pp sample from 2013, which has a factor of 20 higher statistical precision than the 2011 pp data previously presented.

Measurement of the b-jet nuclear modification factors in PbPb collisions at sNN=2.76 TeV with CMS

Modification to jets in high-energy heavy-ion collisions is expected to depend on the flavor of the fragmenting parton. To disentangle this flavor dependence, jets associated to heavy quarks are identified in pp and PbPb collisions. Jets are first tagged by their secondary vertices and the contribution from bottom quarks is extracted using template fits to their secondary vertex mass distributions. In this talk, the b-jet nuclear modification factors are presented in the range of 80 < jet p T < 250 GeV / c , using the full 2011 PbPb and 2013 pp data collected at s N N = 2.76 TeV .

Measurement of jet fragmentation in PbPb andppcollisions atsNN=2.76TeV

The jet fragmentation function of inclusive jets with transverse momentum pt above 100 GeV in PbPb collisions has been measured using reconstructed charged particles with pt above 1 GeV in a cone of radius 0.3 around the jet axis. A data sample of PbPb collisions collected in 2011 at a nucleon-nucleon center-of-mass energy of sqrt(s[NN]) = 2.76 TeV corresponding to an integrated luminosity of 150 inverse microbarns is used. The results for PbPb collisions as a function of collision centrality and jet transverse momentum are compared to reference distributions based on pp data collected at the same center-of-mass energy in 2013, with an integrated luminosity of 5.3 inverse picobarns. A centrality-dependent modification of the fragmentation function is found. For the most central collisions, a significant enhancement is observed in the PbPb / pp fragmentation function ratio for charged particles with pt less than 3 GeV. This enhancement is observed for all jet pt bins studied.

Adsorption of copper to different biogenic oyster shell structures

Abstract The removal of copper from solution by oyster shell powder was investigated for potential wastewater treatment uses. In particular, adsorption behavior differences between the prismatic (PP) and nacreous (NP) shell layers, and how this affects copper removal, were investigated. Experimental results indicated that copper adsorption was highly pH-dependent with optimal copper removal at pH 5.5, where the powdered whole raw shell (RP) removed up to 99.9% of the copper within 24 h at a 10 mg/L initial copper concentration. Langmuir and Freundlich models were used to analyze the isotherm PP, NP and RP data. These results showed a strong homogeneous Langmuir model for low initial copper concentrations (5–30 mg/L) to both RP and PP layer, while strong agreement with a heterogeneous Freundlich model for high initial copper concentrations (30–200 mg/L); nevertheless, a homogeneous Langmuir model provided the best fit for the more dense NP layer across the initial concentration range (5–200 mg/L). The distribution coefficient (Kd) value of PP layer for each initial concentration investigated was substantially higher than the NP layer and it was also found that the PP layer dominated the adsorption process with an adsorption capacity of 8.9 mg/g, while the adsorption capacity of the NP layer was 2.6 mg/g. These differences are believed to be because of the more porous structure of the PP layer, which was confirmed by scanning electron microscopy, infrared spectroscopy, energy-dispersive X-ray spectroscopy, and thermogravimetry–differential thermal analyses.

From ocean-bottom cable seismic to porosity volume: A prestack PP and PS analysis of a turbidite reservoir, deepwater Campos Basin, Brazil

The Campos Basin is the best known and most productive of the Brazilian coastal basins. Turbidites are, by far, the main hydrocarbon-bearing reservoirs in the Campos Basin. Using a 4C ocean-bottom cable seismic survey, we set out to improve the reservoir characterization in a deepwater turbidite field in the Campos Basin. To achieve our goal, prestack angle gathers were derived and PP and PS inversion were performed. The inversion was used as an input to predict the petrophysical properties of the reservoir. Converting seismic reflection amplitudes into impedance profiles not only maximizes vertical resolution but also minimizes tuning effects. Mapping the porosity is extremely important in the development of hydrocarbon reservoirs. Combining seismic attributes derived from the PP and PS multicomponent data and porosity logs, we used linear multiregression and neural networking to predict porosity between the seismic attributes and porosity logs at the well locations. After estimating porosity in the well locations, those relationships were applied to the seismic attributes to generate a 3D porosity volume. The porosity volume highlighted the best reservoir facies in the reservoir. The integration of elastic impedance, shear impedance, and porosity improved the reservoir characterization.

Modification of jet shapes in PbPb collisions at [formula omitted

The first measurement of jet shapes, defined as the fractional transverse momentum radial distribution, for inclusive jets produced in heavy-ion collisions is presented. Data samples of PbPb and pp collisions, corresponding to integrated luminosities of 150 μb−1 and 5.3 pb−1 respectively, were collected at a nucleon–nucleon centre-of-mass energy of sNN=2.76 TeV with the CMS detector at the LHC. The jets are reconstructed with the anti-kT algorithm with a distance parameter R=0.3, and the jet shapes are measured for charged particles with transverse momentum pT>1 GeV/c. The jet shapes measured in PbPb collisions in different collision centralities are compared to reference distributions based on the pp data. A centrality-dependent modification of the jet shapes is observed in the more central PbPb collisions, indicating a redistribution of the energy inside the jet cone. This measurement provides information about the parton shower mechanism in the hot and dense medium produced in heavy-ion collisions.