Abstract A global analysis of ATLAS and CMS measurements reveals that, at mid-rapidity, the directly-produced $$\chi _{c1}$$ χc1 , $$\chi _{c2}$$ χc2 and J/$$\psi $$ ψ mesons have differential cross ...sections of seemingly identical shapes, when presented as a function of the mass-rescaled transverse momentum, $$p_\mathrm{T}/M$$ pT/M . This identity of kinematic behaviours among S- and P-wave quarkonia is certainly not a natural expectation of non-relativistic QCD (NRQCD), where each quarkonium state is supposed to reflect a specific family of elementary production processes, of significantly different $$p_\mathrm{T}$$ pT -differential cross sections. Remarkably, accurate kinematic cancellations among the various NRQCD terms (colour singlets and octets) of its factorization expansion can lead to a surprisingly good description of the data. This peculiar tuning of the NRQCD mixtures leads to a clear prediction regarding the $$\chi _{c1}$$ χc1 and $$\chi _{c2}$$ χc2 polarizations, the only observables not yet measured: they should be almost maximally different from one another, and from the J/$$\psi $$ ψ polarization, a striking exception in the global panorama of quarkonium production. Measurements of the difference between the $$\chi _{c1}$$ χc1 , $$\chi _{c2}$$ χc2 and J/$$\psi $$ ψ polarizations, complementing the observed identity of momentum dependences, represent a decisive probe of NRQCD.
A global analysis of ATLAS and CMS measurements reveals that, at mid-rapidity, the directly-produced
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mesons have differential cross sections of seemingly identical shapes, when presented as a function of the mass-rescaled transverse momentum,
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. This identity of kinematic behaviours among S- and P-wave quarkonia is certainly not a natural expectation of non-relativistic QCD (NRQCD), where each quarkonium state is supposed to reflect a specific family of elementary production processes, of significantly different
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p
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-differential cross sections. Remarkably, accurate kinematic cancellations among the various NRQCD terms (colour singlets and octets) of its factorization expansion can lead to a surprisingly good description of the data. This peculiar tuning of the NRQCD mixtures leads to a clear prediction regarding the
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polarizations, the only observables not yet measured: they should be almost maximally different from one another, and from the J/
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polarization, a striking exception in the global panorama of quarkonium production. Measurements of the difference between the
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χ
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and J/
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ψ
polarizations, complementing the observed identity of momentum dependences, represent a decisive probe of NRQCD.
A global analysis of ATLAS and CMS measurements reveals that, at mid-rapidity, the directly-produced
,
and J/
mesons have differential cross sections of seemingly identical shapes, when presented as ...a function of the mass-rescaled transverse momentum,
. This identity of kinematic behaviours among S- and P-wave quarkonia is certainly not a natural expectation of non-relativistic QCD (NRQCD), where each quarkonium state is supposed to reflect a specific family of elementary production processes, of significantly different
-differential cross sections. Remarkably, accurate kinematic cancellations among the various NRQCD terms (colour singlets and octets) of its factorization expansion can lead to a surprisingly good description of the data. This peculiar tuning of the NRQCD mixtures leads to a clear prediction regarding the
and
polarizations, the only observables not yet measured: they should be almost maximally different from one another, and from the J/
polarization, a striking exception in the global panorama of quarkonium production. Measurements of the difference between the
,
and J/
polarizations, complementing the observed identity of momentum dependences, represent a decisive probe of NRQCD.
The HERA-B experiment has collected data on proton-induced collisions with three fixed nuclear targets at 41.6 GeV centre-of-mass energy. Preliminary results of an ongoing, detailed study of ...charmonium production include the determination of the nuclear dependence of the
J
/
ψ
production kinematics (extending for the first time into the negative-
x
F
region) and precise measurements of the feeddown components due to
χ
c
,
ψ
′
and
b-hadron decays. A new analysis of the
J
/
ψ
decay angular distribution finds significant polarization effects in the low-momentum region, marginally touched by previous experiments. Measurements of the
D-meson cross sections are consistent with the absence of nuclear suppression in open charm production.
The process qq¯→ZZ→4ℓ, dominant background for new physics signals in the four-lepton channel, is characterized by a fully transverse polarization of the two Z bosons with respect to the q and q¯ ...directions. We show that the Z decay angular distributions can be described by a simple, analytical function of the event kinematics, not depending on parton distributions. Using the search for a heavy Higgs boson as an example, we show that the angular discrimination improves the sensitivity to rare signals and is especially beneficial when the background contribution is large.
Computational simulations of protein folding can be used to interpret experimental folding results, to design new folding experiments, and to test the effects of mutations and small molecules on ...folding. However, whereas major experimental and computational progress has been made in understanding how small proteins fold, research on larger, multidomain proteins, which comprise the majority of proteins, is less advanced. Specifically, large proteins often fold via long-lived partially folded intermediates, whose structures, potentially toxic oligomerization, and interactions with cellular chaperones remain poorly understood. Molecular dynamics based folding simulations that rely on knowledge of the native structure can provide critical, detailed information on folding free energy landscapes, intermediates, and pathways. Further, increases in computational power and methodological advances have made folding simulations of large proteins practical and valuable. Here, using serpins that inhibit proteases as an example, we review native-centric methods for simulating the folding of large proteins. These synergistic approaches range from Gō and related structure-based models that can predict the effects of the native structure on folding to all-atom-based methods that include side-chain chemistry and can predict how disease-associated mutations may impact folding. The application of these computational approaches to serpins and other large proteins highlights the successes and limitations of current computational methods and underscores how computational results can be used to inform experiments. These powerful simulation approaches in combination with experiments can provide unique insights into how large proteins fold and misfold, expanding our ability to predict and manipulate protein folding.
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