A
bstract
Of the J/
ψ
mesons (inclusively) produced in pp collisions, a big fraction results from B decays, increasing with transverse momentum and exceeding 50% for
p
T
>
20 GeV. These events must ...be subtracted in measurements of the polarization of prompt J/
ψ
mesons. While several studies have addressed the
ψ
(2S) and
χ
c
impact on the determination of the polarization of the directly-produced J/
ψ
mesons, the theoretical and experimental knowledge of the non-prompt polarization is very poor. Furthermore, non-prompt J/
ψ
polarization measurements can provide interesting information on quarkonium hadroproduction, complementing the studies of prompt production. We review the method of measuring the polarization of non-prompt J/
ψ
mesons (produced in decays of unreconstructed B mesons and detected in the dilepton channel), in conditions typical of LHC experiments studying J/
ψ
production. Realistic model-independent scenarios are validated with data from experiments studying
e
+
e
−
→ Υ(4S) interactions, converted to the high-momentum regime using B differential cross sections measured at the LHC. The non-prompt J/
ψ
polarization measurements are seen to remain dependent on the event selection criteria, even after correcting for the dilepton acceptance and efficiencies. This implies that reproducible definitions of all relevant analysis choices must be reported with the polarization result, for rigorous comparisons with other measurements and/or theoretical calculations. We also discuss how the non-prompt J/
ψ
polarization significantly depends on the relative importance of two complementary B → J
/ψ
decay topologies, two-body (reasonably dominated by singlet production) and multi-body (including octet contributions), providing, hence, valuable information for studies of the charmonium formation mechanisms.
This open-access book addresses the following questions: how does the polarization of a particle, i.e., the angular momentum state in which it is produced, manifest itself in nature? What are the ...concepts and tools needed to perform rigorous measurements providing complete and unambiguous physical information? Polarization measurements are important because they reflect the nature and coupling properties of a particle and provide unique insights into the underlying fundamental interactions, playing a central role in the study and understanding of the mechanisms of particle production. Besides gradually reviewing many fundamental notions, the book presents several case studies relevant to physics analyses underway at the LHC, including the lepton-antilepton decays of vector states (Drell–Yan, Z and W bosons, quarkonia, etc.). The book also offers a detailed discussion of cascade decays, where the vector particle is a daughter of another particle, as well as a survey of typical angular distributions of particles of any integer or half-integer spin. With a visual approach to the presentation of the concepts and frequent use of pedagogical examples, taken from real measurements, gedankenexperiments, or detailed simulations, the book focuses on aspects of polarization measurements that are sometimes underestimated or left unexplored in experimental analyses, such as the importance of the choice of the reference frame, the existence of frame-independent relations, and the shapes of the physically allowed parameter domains. Several examples are provided of pitfalls introduced when the intrinsic multidimensionality of the problem is neglected in exchange for a simplified analysis. Targeting an audience of graduate students, post-docs, and other researchers involved in analyses of LHC data, this book helps to establish a solid bridge between high precision data, existing or soon to be collected, and accurate measurements, including high-sensitivity tests of the Standard Model.
Several fixed-target experiments reported J/ψ and ϒ polarizations, as functions of Feynman x (xF) and transverse momentum (pT), in three different frames, using different combinations of beam ...particles, target nuclei, and collision energies. Despite the diverse and heterogeneous picture formed by these measurements, a detailed look allows us to discern qualitative physical patterns that inspire a simple empirical model. This data-driven scenario offers a good quantitative description of the J/ψ and ϒ(1S) polarizations measured in proton- and pion-nucleus collisions, in the xF≲0.5 domain: more than 80 data points (not statistically independent) are well reproduced with only one free parameter. This study sets the context for future low-pT quarkonium polarization measurements in proton- and pion-nucleus collisions, such as those to be made by the AMBER experiment, and shows that such measurements provide significant constraints on the poorly-known parton distribution functions of the pion.
The observation of unpolarized quarkonium production in high energy pp collisions, at mid rapidity, implies a significant violation of the non-relativistic QCD (NRQCD) velocity scaling rules. A ...precise experimental confirmation of this picture could definitely rule out the current formulation of the factorization expansion. This conclusion relies on current perturbative determinations of the short-distance kinematic factors and may be reverted if improved calculations would modify, in a very specific way, their transverse momentum dependences. That solution would result, however, in a full degeneracy in the presently assumed basis of
2
S
+
1
L
J
Fock states. Therefore, whatever the outcome, improved polarization measurements will challenge and improve our fundamental understanding of quarkonium production.
Measurements made at the LHC have shown that the production of the
J
/
ψ
,
ψ
(
2
S
)
,
Υ
(
1
S
)
and
Υ
(
2
S
)
quarkonia is suppressed in Pb–Pb collisions, with respect to the extrapolation of the pp ...production yields. The
ψ
(
2
S
)
and
Υ
(
2
S
)
states are more strongly suppressed than the ground states and the level of the suppression changes with the centrality of the collision. We show that the measured patterns can be reproduced by a simple model, where all quarkonia are treated in a unified way, starting from the recent realisation that, in pp collisions, the probability of quarkonium formation has a universal dependence on the binding-energy of the bound state. The hot-medium suppression effect is parametrized by a penalty factor in the binding energy, identical for all (S- and P-wave) charmonium and bottomonium states, including those that indirectly contribute to the measured results through feed-down decays. This single parameter, computed through a global fit of all available suppression patterns, fully determines the hierarchy of nuclear effects, for all states and centrality bins. The resulting faithful description of the data provides convincing evidence in favour of the conjecture of sequential quarkonium suppression induced by QGP formation.
Financial advisors seek to accurately measure individuals' risk preferences and provide sound personalized investment advice. Both advice tasks are increasingly offered through automated online ...technologies. Little is known, however, about what drives individuals' acceptance of such automated financial advice and, from a consumer point of view, which firms may be best positioned to provide such advice.
We generate novel insights on these questions by conducting a real-world empirical study using an interactive automated online tool that employs an innovative computer algorithm to build pension investment profiles, the “Pension Builder,” and a large, representative sample.
We focus on the role that two key firm characteristics have on consumer acceptance of pension investment advice generated by computer algorithms running on automated interactive online tools: profit orientation and role in the sales channel.
We find that consumers' perceptions of trust and expertise of the firm providing the automated advice are important drivers of advice acceptance (besides a strong impact of the satisfaction with the consumer–online tool interaction), and that these constructs themselves are clearly influenced by the for-profit vs. not-for-profit orientation and the product provider vs. advisor only role in the sales channel of the firm providing the advice.
We discuss the implications of our findings for marketers and policy makers and provide suggestions for future research.
Dimensional analysis reveals general kinematic scaling rules for the momentum, mass, and energy dependence of Drell–Yan and quarkonium cross sections. Their application to mid-rapidity LHC data ...provides strong experimental evidence supporting the validity of the factorization ansatz, a cornerstone of non-relativistic QCD, still lacking theoretical demonstration. Moreover, data-driven patterns emerge for the factorizable long-distance bound-state formation effects, including a remarkable correlation between the S-wave quarkonium cross sections and their binding energies. Assuming that this scaling can be extended to the P-wave case, we obtain precise predictions for the not yet measured feed-down fractions, thereby providing a complete picture of the charmonium and bottomonium feed-down structure. This is crucial information for quantitative interpretations of quarkonium production data, including studies of the suppression patterns measured in nucleus-nucleus collisions.
Colorectal surgery is associated with postoperative infectious complications in up to 40% of cases, but the diagnosis of these complications is frequently misleading, delaying its resolution. Several ...biomarkers have been shown to be useful in infection diagnosis.
We conducted a single-centre, prospective, observational study segregating patients submitted to elective colorectal surgery with primary anastomosis, CRP and PCT were measured daily. We compared infected and non-infected patients.
From October 2009 to June 2011, a total of 50 patients were included. Twenty-one patients developed infection. PCT and CRP before surgery were equally low in patients with or without postoperative infectious complications. After surgery, both PCT and CRP increased markedly. CRP time-course from the day of surgery onwards was significantly different in infected and non-infected patients (P = 0.001) whereas, PCT time-course was almost parallel in both groups (P = 0.866). Multiple comparisons between infected and non-infected patients from 5th to 9th postoperative days (POD) were performed and CRP concentration was significantly different (P < 0.01, Bonferroni correction), on the 6th, 7th and 8th POD. A CRP concentration > 5.0 mg/dl at the D6 was predictive of infection with a sensitivity of 85% and a specificity of 62% (positive likelihood ratio 2.2, negative likelihood ratio 0.2).
After a major elective surgical insult both CRP and PCT serum levels increased independently of the presence of infection. Besides serum CRP time-course showed to be useful in the early detection of an infectious complication whereas PCT was unhelpful.
The covariance properties of angular momentum eigenstates imply the existence of a rotation-invariant relation among the parameters of the difermion decay distribution of inclusively observed vector ...mesons. This relation is a generalization of the Lam-Tung identity, a result specific to Drell-Yan production in perturbative QCD, here shown to be equivalent to the dynamical condition that the dilepton is always produced transversely polarized with respect to quantization axes belonging to the production plane.
Hard-discounters (HDs) such as Aldi and Lidl are increasingly introducing national brands (NBs) into their private label (PL) dominated assortments. While there is evidence that this enhances sales ...in the categories where such NBs are added, little is known about how it affects consumers' overall perceptions of the HD and consequently its share of the customers' wallet. Using a unique data set that combines longitudinal information on a HD's perceptions, with that chain's assortment composition, we investigate the impact of NB introductions on the chain's overall value and assortment image, and spending share.
We show that introductions of NBs, in particular category leaders, may significantly contribute to a more favorable perception of the HD store. For positive value-image effects to materialize, HDs must offer these NBs at low-enough prices to maintain a reasonable price gap with the current private label offer. For the NB entry to enhance the HD's assortment perception, it must come with a sufficiently deep product line.
However, there are limits to this approach. Introductions gradually lose effect as the share of NBs at the HD goes up. More importantly, ill-selected NB additions may backfire on the HD. Listing NBs that are not category-leaders, at prices too far above its private labels, deteriorates the HD's favorable value positioning — cutting into its core competitive advantage, and leading to notable reductions in share-of-wallet. We discuss the academic and managerial implications of these findings.
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