In search of hair damage using metabolomics?

YesHair fibres are extraordinary materials, not least because they are exquisitely formed by each of the 5 million or so hair follicles on our bodies and have functions that cross from physiology to psychology, but also because they have well known resistance to degradation as seen in hair surviving from archaeological and historical samples [1]. Hair fibres on the head grow at around 1cm each month, together totalling approximately 12km of growth per person per year. Each fibre is incredibly strong for its small diameter; with one fibre typically holding 100g and together a well-formed ponytail [allegedly] has the collective strength to support the weight of a small elephant! Hair – and from here I mean scalp hair – is under constant scrutiny by each of us; whether it be style, split ends, the first few grey hairs or the collection of hairs in the shower that should be firmly attached - leading to the fear that is hair loss

QCD Form Factors and Hadron Helicity Non-Conservation

Recent data for the ratio $R(Q)= QF_{2}(Q^{2})/F_{1}(Q^{2})$ shocked the community by disobeying expectations held for 50 years. We examine the status of perturbative QCD predictions for helicity-flip form factors. Contrary to common belief, we find there is no rule of hadron helicity conservation for form factors. Instead the analysis yields an inequality that the leading power of helicity-flip processes may equal or exceed the power of helicity conserving processes. Numerical calculations support the rule, and extend the result to the regime of laboratory momentum transfer $Q^{2}$. Quark orbital angular momentum, an important feature of the helicity flip processes, may play a role in all form factors at large $Q^{2}$, depending on the quark wave functions.Comment: 25 pages, 5 figure

Proton propagation in nuclei studied in the (e,e’p) reaction

Proton propagation in nuclei was studied using the (e,e’p) reaction in the quasifree region. The coincidence (e,e’p) cross sections were measured at an electron angle of 50.4° and proton angles of 50.1°, 58.2°, 67.9°, and 72.9° for 12C, 27Al, 58Ni, and 181Ta targets at a beam energy of 779.5 MeV. The average outgoing proton energy was 180 MeV. The ratio of the (e,e’p) yield to the simultaneously measured (e,e’) yield was compared to that calculated in the plane-wave impulse approximation and an experimental transmission defined. These experimental transmissions are considerably larger (a factor of ∼2 for 181Ta) than those one would calculate from the free N-N cross sections folded into the nuclear density distribution. A new calculation that includes medium effects (N-N correlations, density dependence of the N-N cross sections and Pauli suppression) accounts for this increase

Cross Section Measurements of Charged Pion Photoproduction in Hydrogen and Deuterium from 1.1 to 5.5 GeV

The differential cross section for the gamma +n --> pi- + p and the gamma + p --> pi+ n processes were measured at Jefferson Lab. The photon energies ranged from 1.1 to 5.5 GeV, corresponding to center-of-mass energies from 1.7 to 3.4 GeV. The pion center-of-mass angles varied from 50 degree to 110 degree. The pi- and pi+ photoproduction data both exhibit a global scaling behavior at high energies and high transverse momenta, consistent with the constituent counting rule prediction and the existing pi+ data. The data suggest possible substructure of the scaling behavior, which might be oscillations around the scaling value. The data show an enhancement in the scaled cross section at center-of-mass energy near 2.2 GeV. The differential cross section ratios at high energies and high transverse momenta can be described by calculations based on one-hard-gluon-exchange diagrams.Comment: 18 pages, 19 figure

Probing the high momentum component of the deuteron at high Q^2

The d(e,e'p) cross section at a momentum transfer of 3.5 (GeV/c)^2 was measured over a kinematical range that made it possible to study this reaction for a set of fixed missing momenta as a function of the neutron recoil angle theta_nq and to extract missing momentum distributions for fixed values of theta_nq up to 0.55 GeV/c. In the region of 35 (deg) <= theta_nq <= 45 (deg) recent calculations, which predict that final state interactions are small, agree reasonably well with the experimental data. Therefore these experimental reduced cross sections provide direct access to the high momentum component of the deuteron momentum distribution in exclusive deuteron electro-disintegration.Comment: 5 pages, 2 figure

Electroexcitation of the Δ+(1232)\Delta^{+}(1232) at low momentum transfer

We report on new p$(e,e^\prime p)\pi^\circ$ measurements at the $\Delta^{+}(1232)$ resonance at the low momentum transfer region. The mesonic cloud dynamics is predicted to be dominant and rapidly changing in this kinematic region offering a test bed for chiral effective field theory calculations. The new data explore the low $Q^2$ dependence of the resonant quadrupole amplitudes while extending the measurements of the Coulomb quadrupole amplitude to the lowest momentum transfer ever reached. The results disagree with predictions of constituent quark models and are in reasonable agreement with dynamical calculations that include pion cloud effects, chiral effective field theory and lattice calculations. The reported measurements suggest that improvement is required to the theoretical calculations and provide valuable input that will allow their refinements

Constraints on the Nucleon Strange Form Factors at Q^2 ~ 0.1 GeV^2

We report the most precise measurement to date of a parity-violating asymmetry in elastic electron-proton scattering. The measurement was carried out with a beam energy of 3.03 GeV and a scattering angle =6 degrees, with the result A_PV = -1.14 +/- 0.24 (stat) +/- 0.06 (syst) parts per million. From this we extract, at Q^2 = 0.099 GeV^2, the strange form factor combination G_E^s + 0.080 G_M^s = 0.030 +/- 0.025 (stat) +/- 0.006 (syst) +/- 0.012 (FF) where the first two errors are experimental and the last error is due to the uncertainty in the neutron electromagnetic form factor. This result significantly improves current knowledge of G_E^s and G_M^s at Q^2 ~0.1 GeV^2. A consistent picture emerges when several measurements at about the same Q^2 value are combined: G_E^s is consistent with zero while G_M^s prefers positive values though G_E^s=G_M^s=0 is compatible with the data at 95% C.L.Comment: minor wording changes for clarity, updated references, dropped one figure to improve focu

Nuclear transparency from quasielastic A(e,e'p) reactions uo to Q^2=8.1 (GeV/c)^2

The quasielastic (e,e$^\prime$p) reaction was studied on targets of deuterium, carbon, and iron up to a value of momentum transfer $Q^2$ of 8.1 (GeV/c)$^2$. A nuclear transparency was determined by comparing the data to calculations in the Plane-Wave Impulse Approximation. The dependence of the nuclear transparency on $Q^2$ and the mass number $A$ was investigated in a search for the onset of the Color Transparency phenomenon. We find no evidence for the onset of Color Transparency within our range of $Q^2$. A fit to the world's nuclear transparency data reflects the energy dependence of the free proton-nucleon cross section.Comment: 11 pages, 6 figure

Virtual Compton Scattering and Neutral Pion Electroproduction in the Resonance Region up to the Deep Inelastic Region at Backward Angles

We have made the first measurements of the virtual Compton scattering (VCS) process via the H$(e,e'p)\gamma$ exclusive reaction in the nucleon resonance region, at backward angles. Results are presented for the $W$-dependence at fixed $Q^2=1$ GeV$^2$, and for the $Q^2$-dependence at fixed $W$ near 1.5 GeV. The VCS data show resonant structures in the first and second resonance regions. The observed $Q^2$-dependence is smooth. The measured ratio of H$(e,e'p)\gamma$ to H$(e,e'p)\pi^0$ cross sections emphasizes the different sensitivity of these two reactions to the various nucleon resonances. Finally, when compared to Real Compton Scattering (RCS) at high energy and large angles, our VCS data at the highest $W$ (1.8-1.9 GeV) show a striking $Q^2$- independence, which may suggest a transition to a perturbative scattering mechanism at the quark level.Comment: 20 pages, 8 figures. To appear in Phys.Rev.

Heavy quarkonium: progress, puzzles, and opportunities

A golden age for heavy quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the $B$-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations. The plethora of newly-found quarkonium-like states unleashed a flood of theoretical investigations into new forms of matter such as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b}, and b\bar{c} bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark-gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K. Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D. Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A. Petrov, P. Robbe, A. Vair