Rapidity Interval Research Articles

Probing double parton scattering via associated open charm and bottom production in ultraperipheral pA collisions

In this article, we propose a novel channel for phenomenological studies of the double-parton scattering (DPS) based upon associated production of charm c{bar{c}} and bottom b{bar{b}} quark pairs in well-separated rapidity intervals in ultraperipheral high-energy proton–nucleus collisions. This process provides direct access to the double-gluon distribution in the proton at small-x and enables one to test the factorized DPS pocket formula. We have made the corresponding theoretical predictions for the DPS contribution to this process at typical LHC energies and beyond and we compute the energy-independent (but photon momentum fraction dependent) effective cross section.

Production of muons from heavy-flavour hadron decays in pp collisions at sqrt{s} = 5.02 TeV

Production cross sections of muons from semi-leptonic decays of charm and beauty hadrons were measured at forward rapidity (2.5 < y < 4) in proton-proton (pp) collisions at a centre-of-mass energy sqrt{s} = 5.02 TeV with the ALICE detector at the CERN LHC. The results were obtained in an extended transverse momentum interval, 2 < pT< 20 GeV/c, and with an improved precision compared to previous measurements performed in the same rapidity interval at centre-of-mass energies sqrt{s} = 2.76 and 7 TeV. The pT- and y-differential production cross sections as well as the pT-differential production cross section ratios between different centre-of-mass energies and different rapidity intervals are described, within experimental and theoretical uncertainties, by predictions based on perturbative QCD.

Multidecadal Historical Trends in Tropical Cyclone Intensity and Evolution Characteristics for Two North Atlantic Subbasins

AbstractThis paper investigates the relationship between long‐term trends (1980–2017) in intensity and wind evolution for tropical cyclones (TCs) within the western tropical Atlantic (WTA) and central/eastern tropical Atlantic (CETA) subbasins. Long‐term TC trends in intensity, intensification time, and wind variability for the CETA were generally more significant than, and in some cases opposite to, those for the WTA. Both the TC intensity levels, as measured by the power dissipation index normalized by storm hours and proportion of rapid intensification intervals (defined as a 12‐hr wind speed increase of 20 kt or more), exhibit no long‐term trends in either subbasin. A TC wind variability index (WVI) calculated over 72‐hr intervals of the TC lifecycle decreases for the WTA over the decades, while the CETA has the 72‐hr intervals with the greatest wind speed fluctuations. The average period of intensification before the peak in TC intensity increases ~0.97 hr/year for the CETA. TC maximum intensity exhibits no trend, suggesting that TCs in the tropical North Atlantic have a trend favoring a longer intensification period to reach their lifetime maximum intensity. A correlation analysis suggests that warmer sea surface temperatures and greater moisture favor longer intensification and greater WVI. In contrast, greater 850‐ to 200‐hPa vertical wind shear is associated with shorter intensification periods and less WVI.

Strongly Intensive Variables and Long-Range Correlations in the Model With a Lattice in the Transverse Plane

In the framework of the quark–gluon string fusion model on the transverse lattice, we study a strongly intensive variable characterizing correlations between the number of particles produced in hadronic interactions in two observation windows separated by a rapidity interval. We show that in the case of independent identical strings, this variable is indeed strongly intensive. It depends only on string characteristics and is independent of trivial so-called volume fluctuations in the string number resulting, in particular, from inevitable impact parameter fluctuations. With string fusion effects causing the production of string clusters with new properties taken into account, this variable turns out to be equal to the weighted average of its values for different string clusters. The weighting coefficients depend on the collision conditions, and the variable loses its strongly intensive character. In the framework of this model in a realistic case with a nonuniform string distribution in the transverse plane, we find explicit analytic formulas for the asymptotic coefficients of long-range correlations between different quantities including an intensive one, the average transverse momentum. We analyze the properties of the obtained correlation coefficients, the studied strongly intensive variable, and also the possibilities of its experimental observation.

Thermodynamic Limit in High-Multiplicity Proton-Proton Collisions at s=7 TeV

An analysis is made of the particle composition in the final state of proton-proton (pp) collisions at 7 TeV as a function of the charged particle multiplicity (dNch/dη). The thermal model is used to determine the chemical freeze-out temperature as well as the radius and strangeness suppression factor γs. Three different ensembles are used in the analysis: the grand canonical ensemble, the canonical ensemble with exact strangeness conservation, and the canonical ensemble with exact baryon number, strangeness, and electric charge conservation. It is shown that for the highest multiplicity class the three ensembles lead to the same result. This allows us to conclude that this multiplicity class is close to the thermodynamic limit. It is estimated that the final state in pp collisions could reach the thermodynamic limit when dNch/dη is larger than twenty per unit of rapidity, corresponding to about 300 particles in the final state when integrated over the full rapidity interval.

SAT-463 Familial X-Linked Acrogigantism: Postnatal Outcomes and Tumor Pathology in a Prenatally Diagnosed Infant and His Affected Mother

Background: X-linked acrogigantism (X-LAG), a condition of infant-onset acrogigantism marked by elevated levels of GH, IGF-1, and PRL, is extremely rare with 33 cases reported in the literature (1), including 7 total familial cases from 3 kindreds. Clinical Case: The patient’s mother, diagnosed with acrogigantism at 21 months of age, underwent pituitary tumor excision at 24 months with the expected subsequent hypopituitarism, diabetes insipidus, and seizure disorder. For over 30 years, stable GH, IGF-1, and PRL levels and serial MRI studies indicated no tumor recurrence. On pre-conception planning genetic studies, X-LAG was diagnosed: SNP microarray showed Xq26.3 microduplication. After conception at age 32, CVS with SNP microarray showed the same microduplication, confirming familial X-LAG in the male fetus (2,3). The infant experienced rapid interval growth between 5-6 months of age in conjunction with rising GH, IGF-1, and PRL levels and enlarging suprasellar pituitary mass, which continued to grow despite titration of bromocriptine started at 6 months. He underwent pituitary tumor resection at 15 months with development of the expected hypopituitarism requiring hormone replacement therapies. The pituitary adenoma resembles the mother’s pituitary adenoma, with tumor cells arranged in trabeculae and glandular structures. Many tumor cells in both cases express GH, PRL and Pit-1. The expression of other lineage-specific transcription factors (T-PIT, SF1) and Sox2 demonstrates the multipotentiality of X-LAG tumors, an observation not previously described. Both tumors showed an elevated Ki-67 proliferation index—5.6% (mother) and 8.5% (patient)—the highest reported in X-LAG (most are < 3%) (1). GH, IGF-1, and PRL levels fell precipitously and growth acceleration decreased, with WHO height Z-score decrease from 2.6 to 1.9 by 20 months of age. Conclusion: This is the first prenatally-diagnosed case of X-LAG. Prospective follow-up with close clinical evaluation provides insight into the natural history of X-LAG. Utilization of cell lineage-specific transcription factors and stem cell markers reveals unexpected complexity of X-LAG tumors.

Beyond nPDFs effects: Prompt J/ψ and ψ(2S) production in pPb and pp collisions

A multi-dimensional analysis of prompt charmonia in pp and pPb collisions at sNN=5.02TeV with the CMS detector is presented. The pPb differential cross-sections of prompt J/ψ are shown in a wide kinematic region, for transverse momentum pT spanning from 2 to 30 GeV/c and a rapidity interval between -2.4 to 1.93 in the center of mass of the collision. The final results on prompt ψ(2S) meson production cross section in pp and pPb collisions at 5.02 TeV are also reported as a function of pT and rapidity, for pT from 4 to 30 GeV/c. The nuclear modification factor is found to be smaller than that of prompt J/ψ in all measured bins, especially at low pT and at backward rapidity. Such a different behaviour between the ground and excited states cannot be reproduced considering nPDF effects alone.

Measurement of the nuclear modification factor for inclusive jets in Pb+Pb collisions at [formula omitted] with the ATLAS detector

Measurements of the yield and nuclear modification factor, RAA, for inclusive jet production are performed using 0.49 nb−1 of Pb+Pb data at sNN=5.02TeV and 25 pb−1 of pp data at s=5.02TeV with the ATLAS detector at the LHC. Jets are reconstructed with the anti-kt algorithm with radius parameter R=0.4 and are measured over the transverse momentum range of 40–1000 GeV in six rapidity intervals covering |y|<2.8. The magnitude of RAA increases with increasing jet transverse momentum, reaching a value of approximately 0.6 at 1 TeV in the most central collisions. The magnitude of RAA also increases towards peripheral collisions. The value of RAA is independent of rapidity at low jet transverse momenta, but it is observed to decrease with increasing rapidity at high transverse momenta.

ϒ suppression at forward rapidity in Pb–Pb collisions at [formula omitted

Inclusive ϒ(1S) and ϒ(2S) production have been measured in Pb–Pb collisions at the centre-of-mass energy per nucleon–nucleon pair sNN=5.02 TeV, using the ALICE detector at the CERN LHC. The ϒ mesons are reconstructed in the centre-of-mass rapidity interval 2.5<y<4 and in the transverse-momentum range pT<15 GeV/c, via their decays to muon pairs. In this Letter, we present results on the inclusive ϒ(1S) nuclear modification factor RAA as a function of collision centrality, transverse momentum and rapidity. The ϒ(1S) and ϒ(2S) RAA, integrated over the centrality range 0–90%, are 0.37±0.02(stat)±0.03(syst) and 0.10±0.04(stat)±0.02(syst), respectively, leading to a ratio RAAϒ(2S)/RAAϒ(1S) of 0.28±0.12(stat)±0.06(syst). The observed ϒ(1S) suppression increases with the centrality of the collision and no significant variation is observed as a function of transverse momentum and rapidity.

Forward Drell-Yan and backward jet production as a probe of the BFKL dynamics

We propose a new process which probes the BFKL dynamics in the high energy proton-proton scattering, namely the forward Drell-Yan (DY) production accompanied by a backward jet, separated from the DY lepton pair by a large rapidity interval. The proposed process probes higher rapidity differences and smaller transverse momenta than in the Mueller-Navelet jet production. It also offers a possibility of measuring new observables like lepton angular distribution coefficients in the DY lepton pair plus jet production.

Measurement of dijet azimuthal decorrelations in pp collisions at s=8 TeV with the ATLAS detector and determination of the strong coupling

A measurement of the rapidity and transverse momentum dependence of dijet azimuthal decorrelations is presented, using the quantity $R_{\Delta \phi}$. The quantity $R_{\Delta \phi}$ specifies the fraction of the inclusive dijet events in which the azimuthal opening angle of the two jets with the highest transverse momenta is less than a given value of the parameter $\Delta \phi_\mathrm{max}$. The quantity $R_{\Delta \phi}$ is measured in proton--proton collisions at $\sqrt{s}=$8 TeV as a function of the dijet rapidity interval, the event total scalar transverse momentum, and $\Delta \phi_\mathrm{max}$. The measurement uses an event sample corresponding to an integrated luminosity of 20.2 fb$^{-1}$ collected with the ATLAS detector at the CERN Large Hadron Collider. Predictions of a perturbative QCD calculation at next-to-leading order in the strong coupling with corrections for non-perturbative effects are compared to the data. The theoretical predictions describe the data in the whole kinematic region. The data are used to determine the strong coupling $\alpha_{\mathrm{S}}$ and to study its running for momentum transfers from 260 GeV to above 1.6 TeV. An analysis that combines data at all momentum transfers results in $\alpha_{\mathrm{S}}(m_{Z}) = 0.1127^{+0.0063}_{-0.0027}$.

A New Method of Integrating the Equations of Autonomous Strapdown INS

We propose the new version of separating the process of integrating the differential equations, which describe the functioning of the strapdown inertial navigation system (SINS) in the normal geographic coordinate system (NGCS), into rapid and slow cycles. In this version, the vector of the relative velocity of an object is represented as a sum of a rapidly changing component and a slowly changing component. The equation for the rapidly changing component of the relative velocity includes the vectors of angular velocities of the Earth’s rotation, NGCS rotation, and, at the same time, the vectors of the apparent acceleration and gravity acceleration, because these accelerations partially balance each other, and at rest relative to the Earth are balanced completely. The equation of the slowly changing component of the relative velocity includes only the vector of angular velocity of the Earth’s rotation and the vector of NGCS rotation. The quaternion orientation of an object relative to the NGCS is represented as a product of two quaternions: a rapidly changing one, which is determined by the absolute angular velocity of an object, and slowly changing one, which is determined by the angular velocity of the NGCS. The right parts of the equations for each group of variables depend on the rapidly changing and slowly changing variables. In order to enable the independent integration of the slow and rapid cycle equations, the algorithm have been developed for integrating the equations using the predictor and corrector for the cases of instantaneous and integral information generated by SINS sensors. At each predictor step the Euler method is used to estimate the longitude, latitude and altitude of an object, slowly changing component of the relative velocity, and slowly changing multiplier of the orientation quaternion at the rightmost point of the slow cycle. Then the Euler-Cauchy method is used to integrate the equations for the rapidly changing components on the rapid cycle intervals, which are present in the slow cycle. The necessary values of the slowly changing components in the intermediate points are calculated using the formulas of linear interpolation. After the rapidly changing components are estimated at the rightmost point of the slow cycle, at the corrector step the Euler-Cauchy method is used to refine the values of the slowly changing components at the rightmost point of the slow cycle. Note that at the beginning of each slow cycle step the slowly changing component of velocity is equal to the value of the relative velocity of an object, and the rapidly changing component is zero. Similarly, at the beginning of each slow cycle step the slowly changing multiplier of object’s orientation quaternion equals to the quaternion of orientation of an object relative to the NGCS, and the rapidly changing multiplier of the orientation of an object has its scalar part equal to one, and its vector part equal to zero (this formula is derived from the quaternion formula for adding the finite rotations). SINS on a stationary base had been simulated in the presence of perturbations for a large time interval for a diving object, which drastically changes its height over short time periods.

Inclusive J/ψ production in Xe–Xe collisions at [formula omitted] TeV

Inclusive J/ψ production is studied in Xe–Xe interactions at a centre-of-mass energy per nucleon pair of sNN=5.44 TeV, using the ALICE detector at the CERN LHC. The J/ψ meson is reconstructed via its decay into a muon pair, in the centre-of-mass rapidity interval 2.5<y<4 and down to zero transverse momentum. In this Letter, the nuclear modification factors RAA for inclusive J/ψ, measured in the centrality range 0–90% as well as in the centrality intervals 0–20% and 20–90% are presented. The RAA values are compared to previously published results for Pb–Pb collisions at sNN=5.02 TeV and to the calculation of a transport model. A good agreement is found between Xe–Xe and Pb–Pb results as well as between data and the model.

Inclusive J/\u03c8 production at forward and backward rapidity in p-Pb collisions at sqrt{s_{mathrm{NN}}}=8.16 TeV

Inclusive J/ψ production is studied in p-Pb interactions at a centre-of-mass energy per nucleon-nucleon collision sqrt{s_{mathrm{NN}}}=8.16 TeV, using the ALICE detector at the CERN LHC. The J/ψ meson is reconstructed, via its decay to a muon pair, in the centre-of-mass rapidity intervals 2.03 < ycms < 3.53 and −4.46 < ycms < −2.96, where positive and negative ycms refer to the p-going and Pb-going direction, respectively. The transverse momentum coverage is pT < 20 GeV/c. In this paper, ycms- and pT-differential cross sections for inclusive J/ψ production are presented, and the corresponding nuclear modification factors RpPb are shown. Forward results show a suppression of the J/ψ yield with respect to pp collisions, concentrated in the region pT ≲ 5 GeV/c. At backward rapidity no significant suppression is observed. The results are compared to previous measurements by ALICE in p-Pb collisions at sqrt{s_{mathrm{NN}}}=5.02 TeV and to theoretical calculations. Finally, the ratios RFB between forward- and backward-ycmsRpPb values are shown and discussed.

Measurement of the inclusive J/psi polarization at forward rapidity in pp collisions at mathbf {sqrt{s} = 8}\xa0TeV

We report on the measurement of the inclusive J/psi polarization parameters in pp collisions at a center of mass energy sqrt{s} = 8 TeV with the ALICE detector at the LHC. The analysis is based on a data sample corresponding to an integrated luminosity of 1.23 pb^{-1}. J/psi resonances are reconstructed in their di-muon decay channel in the rapidity interval 2.5< y < 4.0 and over the transverse-momentum interval 2< p_mathrm{T} < 15 mathrm {GeV}/c. The three polarization parameters (lambda _theta , lambda _varphi , lambda _{theta varphi }) are measured as a function of p_mathrm{T} both in the helicity and Collins-Soper reference frames. The measured J/psi polarization parameters are found to be compatible with zero within uncertainties, contrary to expectations from all available predictions. The results are compared with the measurement in pp collisions at sqrt{s} = 7 TeV.

Phi meson production at forward rapidity in Pb\u2013Pb collisions at sqrt{s_mathrm {NN}}=2.76\xa0TeV

phi meson measurements provide insight into strangeness production, which is one of the key observables for the hot medium formed in high-energy heavy-ion collisions. ALICE measured phi production through its decay in muon pairs in Pb–Pb collisions at sqrt{s_mathrm {NN}} = 2.76 TeV in the intermediate transverse momentum range 2< p_mathrm {T}< 5 GeV/c and in the rapidity interval 2.5<y<4. The phi yield was measured as a function of the transverse momentum and collision centrality. The nuclear modification factor was obtained as a function of the average number of participating nucleons. Results were compared with the ones obtained via the kaon decay channel in the same p_mathrm {T} range at midrapidity. The values of the nuclear modification factor in the two rapidity regions are in agreement within uncertainties.

\u039bc+ production in pp collisions at sqrt{s}=7 TeV and in p-Pb collisions at sqrt{s_{mathrm{NN}}}=5.02 TeV

The pT-differential production cross section of prompt Λc+ charmed baryons was measured with the ALICE detector at the Large Hadron Collider (LHC) in pp collisions at sqrt{s}=7 TeV and in p-Pb collisions at sqrt{s_{mathrm{NN}}}=5.02 TeV at midrapidity. The Λc+ and {overline{varLambda}}_{overline{mathrm{c}}} were reconstructed in the hadronic decay modes Λc+ → pK−π+, Λc+ → pKS0 and in the semileptonic channel Λc+ → e+νeΛ (and charge conjugates). The measured values of the Λc+/D0 ratio, which is sensitive to the c-quark hadronisation mechanism, and in particular to the production of baryons, are presented and are larger than those measured previously in different colliding systems, centre-of-mass energies, rapidity and pT intervals, where the Λc+ production process may differ. The results are compared with the expectations obtained from perturbative Quantum Chromodynamics calculations and Monte Carlo event generators. Neither perturbative QCD calculations nor Monte Carlo models reproduce the data, indicating that the fragmentation of heavy-flavour baryons is not well understood. The first measurement at the LHC of the Λc+ nuclear modification factor, RpPb, is also presented. The RpPb is found to be consistent with unity and with that of D mesons within the uncertainties, and consistent with a theoretical calculation that includes cold nuclear matter effects and a calculation that includes charm quark interactions with a deconfined medium.

Transverse momentum spectra of hadrons in p + p collisions at CERN SPS energies from the UrQMD transport model

The UrQMD transport model, version 3.4, is used to study the new experimental data on transverse momentum spectra of π±, K±, p and p¯ produced in inelastic p+p interactions at SPS energies, recently published by the NA61/SHINE Collaboration. The comparison of model predictions to these new measurements is presented as a function of collision energy for central and forward particle rapidity intervals. In addition, the inverse slope parameters characterizing the transverse momentum distributions are extracted from the predicted spectra and compared to the corresponding values obtained from NA61/SHINE distributions, as a function of particle rapidity and collision energy. A complex pattern of deviations between the experimental data and the UrQMD model emerges. For charged pions, the fair agreement visible at top SPS energies deteriorates with the decreasing energy. For charged K mesons, UrQMD significantly underpredicts positive kaon production at lower beam momenta. It also underpredicts the central rapidity proton yield at top collision energy and overpredicts antiproton production at all considered energies. We conclude that the new experimental data analyzed in this paper still constitute a challenge for the present version of the model.

Σ0 production in proton nucleus collisions near threshold

The production of Σ0 baryons in the nuclear reaction p (3.5 GeV) + Nb (corresponding to sNN=3.18 GeV) is studied with the detector set-up HADES at GSI, Darmstadt. Σ0s were identified via the decay Σ0→Λγ with subsequent decays Λ→pπ− in coincidence with a e+e− pair from either external (γ→e+e−) or internal (Dalitz decay γ⁎→e+e−) gamma conversions. The differential Σ0 cross section integrated over the detector acceptance, i.e. the rapidity interval 0.5<y<1.1, has been extracted as ΔσΣ0=2.3±(0.2)stat±(−0.6+0.6)sys±(0.2)norm mb, yielding the inclusive production cross section in full phase space σΣ0total=5.8±(0.5)stat±(−1.4+1.4)sys±(0.6)norm±(1.7)extrapol mb by averaging over different extrapolation methods. The Λall/Σ0 ratio within the HADES acceptance is equal to 2.3±(0.2)stat±(−0.6+0.6)sys. The obtained rapidity and momentum distributions are compared to transport model calculations. The Σ0 yield agrees with the statistical model of particle production in nuclear reactions.

Production of deuterons, tritons, He3 nuclei, and their antinuclei in pp collisions at s=0.9 , 2.76, and 7 TeV

Invariant differential yields of deuterons and anti-deuterons in pp collisions at $\sqrt{s}$ = 0.9, 2.76 and 7 TeV and the yields of tritons, $^{3}$He nuclei and their anti-nuclei at $\sqrt{s}$ = 7 TeV have been measured with the ALICE detector at the CERN Large Hadron Collider. The measurements cover a wide transverse momentum ($p_{\text{T}}$) range in the rapidity interval $|y|<0.5$, extending both the energy and the $p_{\text{T}}$ reach of previous measurements up to 3 GeV/$c$ for $A=2$ and 6 GeV/$c$ for $A=3$. The coalescence parameters of (anti-)deuterons and $^{3}\overline{\text{He}}$ nuclei exhibit an increasing trend with $p_{\text{T}}$ and are found to be compatible with measurements in pA collisions at low $p_{\text{T}}$ and lower energies. The integrated yields decrease by a factor of about 1000 for each increase of the mass number with one (anti-)nucleon. Furthermore, the deuteron-to-proton ratio is reported as a function of the average charged particle multiplicity at different center-of-mass energies.