High-precision HERA data corresponding to a luminosity of around 1 fb-1 have been used in the framework of eeqq contact interactions (CI) to set limits on possible high-energy contributions beyond ...the Standard Model to electron-quark scattering. Measurements of the inclusive deep inelastic cross sections in neutral and charged current ep scattering were considered. The analysis of the ep data has been based on simultaneous fits of parton distribution functions including contributions of CI couplings to ep scattering. Several general CI models and scenarios with heavy leptoquarks were considered. Improvements in the description of the inclusive HERA data were obtained for a few models. Since a statistically significant deviation from the Standard Model cannot be established, limits in the TeV range were set on all models considered.
Phys. Rev. D 89, 072007 (2014) The neutral current e+/-p cross section has been measured up to values of
Bjorken x of approximately 1 with the ZEUS detector at HERA using an integrated
luminosity of ...187 inv. pb of e-p and 142 inv. pb of e+p collisions at sqrt(s) =
318GeV. Differential cross sections in x and Q2, the exchanged boson
virtuality, are presented for Q2 geq 725GeV2. An improved reconstruction method
and greatly increased amount of data allows a finer binning in the high-x
region of the neutral current cross section and leads to a measurement with
much improved precision compared to a similar earlier analysis. The
measurements are compared to Standard Model expectations based on a variety of
recent parton distribution functions.
Serial femtosecond crystallography (SFX) with X-ray free electron lasers (XFELs) allows structure determination of membrane proteins and time-resolved crystallography. Common liquid sample delivery ...continuously jets the protein crystal suspension into the path of the XFEL, wasting a vast amount of sample due to the pulsed nature of all current XFEL sources. The European XFEL (EuXFEL) delivers femtosecond (fs) X-ray pulses in trains spaced 100 ms apart whereas pulses within trains are currently separated by 889 ns. Therefore, continuous sample delivery via fast jets wastes >99% of sample. Here, we introduce a microfluidic device delivering crystal laden droplets segmented with an immiscible oil reducing sample waste and demonstrate droplet injection at the EuXFEL compatible with high pressure liquid delivery of an SFX experiment. While achieving ~60% reduction in sample waste, we determine the structure of the enzyme 3-deoxy-D-manno-octulosonate-8-phosphate synthase from microcrystals delivered in droplets revealing distinct structural features not previously reported.
The European XFEL is a megahertz repetition-rate facility producing extremely bright and coherent pulses of a few tens of femtoseconds duration. The amount of data generated in the context of user ...experiments can exceed hundreds of gigabits per second, resulting in tens of petabytes stored every year. These rates and volumes pose significant challenges both for facilities and users thereof. In fact, if unaddressed, extraction and interpretation of scientific content will be hindered, and investment and operational costs will quickly become unsustainable. In this article, we outline challenges and solutions in data reduction.
The European X-ray Free Electron Laser (XFEL) and Linac Coherent Light Source (LCLS) II are extremely intense sources of X-rays capable of generating Serial Femtosecond Crystallography (SFX) data at ...megahertz (MHz) repetition rates. Previous work has shown that it is possible to use consecutive X-ray pulses to collect diffraction patterns from individual crystals. Here, we exploit the MHz pulse structure of the European XFEL to obtain two complete datasets from the same lysozyme crystal, first hit and the second hit, before it exits the beam. The two datasets, separated by <1 µs, yield up to 2.1 Å resolution structures. Comparisons between the two structures reveal no indications of radiation damage or significant changes within the active site, consistent with the calculated dose estimates. This demonstrates MHz SFX can be used as a tool for tracking sub-microsecond structural changes in individual single crystals, a technique we refer to as multi-hit SFX.
An experimental platform for dynamic diamond anvil cell (dDAC) research has been developed at the High Energy Density (HED) Instrument at the European X‐ray Free Electron Laser (European XFEL). ...Advantage was taken of the high repetition rate of the European XFEL (up to 4.5 MHz) to collect pulse‐resolved MHz X‐ray diffraction data from samples as they are dynamically compressed at intermediate strain rates (≤103 s−1), where up to 352 diffraction images can be collected from a single pulse train. The set‐up employs piezo‐driven dDACs capable of compressing samples in ≥340 µs, compatible with the maximum length of the pulse train (550 µs). Results from rapid compression experiments on a wide range of sample systems with different X‐ray scattering powers are presented. A maximum compression rate of 87 TPa s−1 was observed during the fast compression of Au, while a strain rate of ∼1100 s−1 was achieved during the rapid compression of N2 at 23 TPa s−1.
A MHz X‐ray diffraction set‐up for the investigation of material behaviour under dynamic compression in a diamond anvil cell at intermediate strain rates has been developed at the High Energy Density (HED) instrument at the European XFEL.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
A search for a narrow baryonic state in the \(pK^0_S\) and \(\bar{p}K^0_S\) system has been performed in \(ep\) collisions at HERA with the ZEUS detector using an integrated luminosity of 358 ...pb\(^{-1}\) taken in 2003-2007. The search was performed with deep inelastic scattering events at an \(ep\) centre-of-mass energy of 318 GeV for exchanged photon virtuality, \(Q^2\), between 20 and 100 \(\rm{} GeV^{2}\). Contrary to evidence presented for such a state around 1.52 GeV in a previous ZEUS analysis using a sample of 121 pb\(^{-1}\) taken in 1996-2000, no resonance peak was found in the \(p(\bar{p})K^0_S\) invariant-mass distribution in the range 1.45-1.7 GeV. Upper limits on the production cross section are set.
The high-precision HERA data allows searches up to TeV scales for Beyond the Standard Model contributions to electron-quark scattering. Combined measurements of the inclusive deep inelastic cross ...sections in neutral and charged current \(ep\) scattering corresponding to a luminosity of around 1 fb\(^{-1}\) have been used in this analysis. A new approach to the beyond the Standard Model analysis of the inclusive \(ep\) data is presented; simultaneous fits of parton distribution functions together with contributions of "new physics" processes were performed. Results are presented considering a finite radius of quarks within the quark form-factor model. The resulting 95% C.L. upper limit on the effective quark radius is \(0.43\cdot 10^{-16}\) cm.
The neutral current ${e}^{±}p$ cross section has been measured up to values of Bjorken $x\cong 1$ with the ZEUS detector at HERA using an integrated luminosity of ...$187\text{}\text{}{\mathrm{pb}}^{-1}$ of ${e}^{-}p$ and $142\text{}\text{}{\mathrm{pb}}^{-1}$ of ${e}^{+}p$ collisions at $\sqrt{s}=318\text{}\text{}\mathrm{GeV}$. Differential cross sections in $x$ and ${Q}^{2}$, the exchanged boson virtuality, are presented for ${Q}^{2}\ge 725\text{}\text{}{\mathrm{GeV}}^{2}$. An improved reconstruction method and greatly increased amount of data allows a finer binning in the high-$x$ region of the neutral current cross section and leads to a measurement with much improved precision compared to a similar earlier analysis. The measurements are compared to Standard Model expectations based on a variety of recent parton distribution functions.
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