Quasi-elastic polarization-transfer measurements on the deuteron in anti-parallel kinematics

We present measurements of the polarization-transfer components in the H2(e→,e′p→) reaction, covering a previously unexplored kinematic region with large positive (anti-parallel) missing momentum, pmiss, up to 220MeV/c, and Q2=0.65 (GeV/c)2. These measurements, performed at the Mainz Microtron (MAMI), were motivated by theoretical calculations which predict small final-state interaction (FSI) effects in these kinematics, making them favorable for searching for medium modifications of bound nucleons in nuclei. We find in this kinematic region that the measured polarization-transfer components Px and Pz and their ratio agree with the theoretical calculations, which use free-proton form factor…

Observation ofHΛ4Hyperhydrogen by Decay-Pion Spectroscopy in Electron Scattering

At the Mainz Microtron MAMI, the first high-resolution pion spectroscopy from decays of strange systems was performed by electron scattering off a ^9B

Technical design of the phase I Mu3e experiment

Nuclear instruments & methods in physics research / A 1014, 165679 (2021). doi:10.1016/j.nima.2021.165679

Components of polarization-transfer to a bound proton in a deuteron measured by quasi-elastic electron scattering

We report the first measurements of the transverse (Px and Py) and longitudinal (Pz) components of the polarization transfer to a bound proton in the deuteron via the H2(e→,e′p→) reaction, over a wide range of missing momentum. A precise determination of the electron beam polarization reduces the systematic uncertainties on the individual components to a level that enables a detailed comparison to a state-of-the-art calculation of the deuteron using free-proton electromagnetic form factors. We observe very good agreement between the measured and the calculated Px/Pz ratios, but deviations of the individual components. Our results cannot be explained by medium modified electromagnetic form f…

The influence of Fermi motion on the comparison of the polarization transfer to a proton in elastic e→p and quasi-elastic e→A scattering

Abstract A comparison between polarization-transfer to a bound proton in quasi-free kinematics by the A ( e → , e ′ p → ) knockout reaction and that in elastic scattering off a free proton can provide information on the characteristics of the bound proton. In the past the reported measurements have been compared to those of a free proton with zero initial momentum. We introduce, for the first time, expressions for the polarization-transfer components when the proton is initially in motion and compare them to the 2H data measured at the Mainz Microtron (MAMI). We show the ratios of the transverse ( P x ) and longitudinal ( P z ) components of the polarization transfer in H 2 ( e → , e ′ p → …

Performance of the ATLASPix1 pixel sensor prototype in ams aH18 CMOS technology for the ATLAS ITk upgrade

Effect of the phase behaviour of the solvent–antisolvent systems on the gas–antisolvent-crystallisation of paracetamol

Abstract The influence of the phase behaviour of the solvent–antisolvent system on the process conditions for the gas–antisolvent process is investigated. The two fluids are modelled by the Peng–Robinson equation of state while the dissolved solid is described by a Clapeyron-type approach. Based on the correlation of the ternary system, a liquid–liquid immiscibility region has been found which hinders the proper crystallisation of the solute. A thorough investigation of the binary solvent–antisolvent system by the global phase diagram methods yields a criterion for the proper choice of the solvent. The crucial property turns out to be the distance of the solvent–antisolvent system from the …

The BIOSAFEPAPER project for in vitro toxicity assessments: preparation, detailed chemical characterisation and testing of extracts from paper and board samples

International audience; Nineteen food contact papers and boards and one non-food contact board were extracted following test protocols developed within European Union funded project BIOSAFEPAPER. The extraction media were either hot or cold water, 95% ethanol or Tenax, according to the end use of the sample. The extractable dry matter content of the samples varied from 1200 to 11,800 mg/kg (0.8-35.5 mg/dm2). According to GC-MS the main substances extracted into water were pulp-derived natural products such as fatty acids, resin acids, natural wood sterols and alkanols. Substances extracted into ethanol particularly, were diisopropylnaphthalenes, alkanes and phthalic acid esters. The non-foo…

Search at the Mainz Microtron for light massive gauge bosons relevant for the muon g-2 anomaly.

A massive, but light, Abelian U(1) gauge boson is a well-motivated possible signature of physics beyond the standard model of particle physics. In this Letter, the search for the signal of such a U(1) gauge boson in electron-positron pair production at the spectrometer setup of the A1 Collaboration at the Mainz Microtron is described. Exclusion limits in the mass range of 40  MeV/c^{2} to 300  MeV/c^{2}, with a sensitivity in the squared mixing parameter of as little as ε^{2}=8×10^{-7} are presented. A large fraction of the parameter space has been excluded where the discrepancy of the measured anomalous magnetic moment of the muon with theory might be explained by an additional U(1) gauge …

Measurements of the induced polarization in the quasi-elastic A(e,e′p→) process in non-coplanar kinematics

Abstract We report measurements of the induced polarization P → of protons knocked out from 2H and 12C via the A ( e , e ′ p → ) reaction. We have studied the dependence of P → on two kinematic variables: the missing momentum p miss and the “off-coplanarity” angle ϕ p q between the scattering and reaction planes. For the full 360° range in ϕ p q , both the normal ( P y ) and, for the first time, the transverse ( P x ) components of the induced polarization were measured with respect to the coordinate system associated with the scattering plane. P x vanishes in coplanar kinematics, however in non-coplanar kinematics, it is on the same scale as P y . We find that the dependence on ϕ p q is si…

Measurements of the electron-helicity asymmetry in the quasi-elastic A(e→,e′p) process

Abstract We present measurements of the electron helicity asymmetry in quasi-elastic proton knockout from 2H and 12C nuclei by polarized electrons. This asymmetry depends on the fifth structure function, is antisymmetric with respect to the scattering plane, and vanishes in the absence of final-state interactions, and thus it provides a sensitive tool for their study. Our kinematics cover the full range in off-coplanarity angle ϕ p q , with a polar angle θ p q coverage up to about 8°. The missing energy resolution enabled us to determine the asymmetries for knock-out resulting in different states of the residual 11B system. We find that the helicity asymmetry for p-shell knockout from 12C d…

First measurement of proton's charge form factor at very low $Q^2$ with initial state radiation

We report on a new experimental method based on initial-state radiation (ISR) in e-p scattering, in which the radiative tail of the elastic e-p peak contains information on the proton charge form factor ($G_E^p$) at extremely small $Q^2$. The ISR technique was validated in a dedicated experiment using the spectrometers of the A1-Collaboration at the Mainz Microtron (MAMI). This provided first measurements of $G_E^p$ for $0.001\leq Q^2\leq 0.004 (GeV/c)^2$.

Ground-state binding energy of HΛ4 from high-resolution decay-pion spectroscopy

Abstract A systematic study on the Λ ground state binding energy of hyperhydrogen H Λ 4 measured at the Mainz Microtron MAMI is presented. The energy was deduced from the spectroscopy of mono-energetic pions from the two-body decays of hyperfragments, which were produced and stopped in a 9Be target. First data, taken in the year 2012 with a high resolution magnetic spectrometer, demonstrated an almost one order of magnitude higher precision than emulsion data, while being limited by systematic uncertainties. In 2014 an extended measurement campaign was performed with improved control over systematic effects, increasing the yield of hypernuclei and confirming the observation with two indepen…

Safety assessment of food-contact paper and board using a battery of short-term toxicity tests: European union BIOSAFEPAPER project.

International audience; An European Union (EU)-funded project QLK1-CT-2001-00930 (BIOSAFEPAPER) involves the development, validation and intercalibration of a short-term battery of toxicological tests for the safety assessment of food-contact paper and board. Dissemination of the results to industry, legislators (e.g. DG Consumer Protection, DG Enterprises, DG Research), standardization bodies such as CEN, and consumers will create an agreed risk evaluation procedure. The project involves pre-normative research in order to establish a set of in-vitro cytotoxicity and genotoxicity tests that will be easily adaptable to food-contact fibre-based materials and have endpoints relevant to consume…

Status and recent developments at the polarized-electron injector of the superconducting Darmstadt electron linear accelerator S-DALINAC

At the superconducting Darmstadt electron linac a 100 keV source of polarized electrons has been installed. Major components had been tested prior to installation at an offline teststand. Commissioning of the new source at the S-DALINAC will take place early in 2011. We report on the performance of the teststand, simulations, developments on the laser systems, new radio-frequency components for the S-DALINAC injector, and the status of the implementation of the source.

Test procedures for obtaining representative extracts suitable for reliable in vitro toxicity assessment of paper and board intended for food contact.

International audience; This paper describes the use of a suite of extraction procedures applicable to the assessment of the in vitro toxicity of paper/board samples intended for food-contact applications. The sample is extracted with ethanol, water, or exposed to modified polyphenylene oxide (Tenax) for fatty, non-fatty and dry food applications, respectively. The water extracts are directly suitable for safety assessment using in vitro bioassays. The ethanol extracts of the paper/board and of the exposed Tenax require pre-concentration to give acceptable sensitivity. This is because the in vitro bioassays can tolerate only a small percentage of added organic solvent before the solvent its…

Safety Evaluation of Food contact paper and board using Chemical Tests and in vitro Bioassays-The role of known and unknown substances

International audience; In vitro toxicological tests has have been proposed as an approach to complement the chemical safety assessment of food contact materials, particularly those with a complex or unknown chemical composition such as paper and board. An EU 5th framework program project “BIOSAFEPAPER – Application of bioassays for safety assessment of paper and board for food contact” specially focused on the application of biotests to paper and board. The project included both chemical characterization and toxicological testing of a representative number of paper and board extracts prepared according to the proposed end use (wet, fatty and dry food contact). Among the concerns addressed …

Comparison of recoil polarization in the C12(e→,e′p→) process for protons extracted from s and p shells

Abstract We present the first measurements of the double ratio of the polarization-transfer components ( P x ′ / P z ′ ) p / ( P x ′ / P z ′ ) s for knock-out protons from the s and p shells in C 12 measured by the C 12 ( e → , e ′ p → ) reaction in quasi-elastic kinematics. The data are compared to theoretical predictions in the relativistic distorted-wave impulse approximation. Our results show that the differences between s- and p-shell protons, observed when compared at the same initial momentum (missing momentum), largely disappear when the comparison is done at the same proton virtuality. We observe no difference in medium modifications between protons from the s and p shells with the…

Measurement of polarization-transfer to bound protons in carbon and its virtuality dependence

We measured the ratio Px/Pz of the transverse to longitudinal components of polarization transferred from electrons to bound protons in C12 by the C12(e→,e′p→) process at the Mainz Microtron (MAMI). We observed consistent deviations from unity of this ratio normalized to the free-proton ratio, (Px/Pz)C12/(Px/Pz)H1, for both s- and p-shell knocked out protons, even though they are embedded in averaged local densities that differ by about a factor of two. The dependence of the double ratio on proton virtuality is similar to the one for knocked out protons from H2 and He4, suggesting a universal behavior. It further implies no dependence on average local nuclear density.

Simultaneous measurement of the muon neutrino charged-current cross section on oxygen and carbon without pions in the final state at T2K

Authors: K. Abe,56 N. Akhlaq,45 R. Akutsu,57 A. Ali,32 C. Alt,11 C. Andreopoulos,54,34 L. Anthony,21 M. Antonova,19 S. Aoki,31 A. Ariga,2 T. Arihara,59 Y. Asada,69 Y. Ashida,32 E. T. Atkin,21 Y. Awataguchi,59 S. Ban,32 M. Barbi,46 G. J. Barker,66 G. Barr,42 D. Barrow,42 M. Batkiewicz-Kwasniak,15 A. Beloshapkin,26 F. Bench,34 V. Berardi,22 L. Berns,58 S. Bhadra,70 S. Bienstock,53 S. Bolognesi,6 T. Bonus,68 B. Bourguille,18 S. B. Boyd,66 A. Bravar,13 D. Bravo Berguño,1 C. Bronner,56 S. Bron,13 A. Bubak,51 M. Buizza Avanzini ,10 T. Campbell,7 S. Cao,16 S. L. Cartwright,50 M. G. Catanesi,22 A. Cervera,19 D. Cherdack,17 N. Chikuma,55 G. Christodoulou,12 M. Cicerchia,24,† J. Coleman,34 G. Collazu…

Polarization-transfer measurement to a large-virtuality bound proton in the deuteron

Possible differences between free and bound protons may be observed in the ratio of polarization-transfer components, $P'_x/P'_z$. We report the measurement of $P'_x/P'_z$, in the $^2\textrm{H}(\vec{e},e^{\prime}\vec{p})n$ reaction at low and high missing momenta. Observed increasing deviation of $P'_x/P'_z$ from that of a free proton as a function of the virtuality, similar to that observed in \hefour, indicates that the effect in nuclei is due to the virtuality of the knock-out proton and not due to the average nuclear density. The measured differences from calculations assuming free-proton form factors ($\sim10\%$), may indicate in-medium modifications.

New Insight in the $Q^2$-Dependence of Proton Generalized Polarizabilities

Virtual Compton scattering on the proton has been investigated at three yet unexplored values of the four-momentum transfer $Q^2$: 0.10, 0.20 and 0.45 GeV$^2$, at the Mainz Microtron. Fits performed using either the low-energy theorem or dispersion relations allowed the extraction of the structure functions $P_{LL} -P_{TT} / \epsilon$ and $P_{LT}$, as well as the electric and magnetic generalized polarizabilities $\alpha_{E1}(Q^2)$ and $\beta_{M1}(Q^2)$. These new results show a smooth and rapid fall-off of $\alpha_{E1}(Q^2)$, in contrast to previous measurements at $Q^2$ = 0.33 GeV$^2$, and provide for the first time a precise mapping of $\beta_{M1}(Q^2)$ in the low-$Q^2$ region.

Experimental investigations of the hypernucleus $_Λ^4$H

International audience; Negatively charged pions from two-body decays of stopped _Lambda^4H hypernuclei were studied in 2012 at the Mainz Microtron MAMI, Germany. The momenta of the decay-pions were measured with unprecedented precision by using high-resolution magnetic spectrometers. A challenge of the experiment was the tagging of kaons from associated K^+∧ production off a Be target at very forward angles. In the year 2014, this experiment was continued with a better control of the systematic uncertainties, with better suppression of coincident and random background, improved particle identification, and with higher luminosities. Another key point of the progress was the improvemen…

Prospects for hypernuclear physics at Mainz: From KAOS@MAMI to PANDA@FAIR

Abstract At the Mainz Microtron hypernuclei are produced by ( e , e ′ K ) reactions. A dedicated kaon spectrometer located at 0° with respect to the electron beam is used to detect kaons emitted in forward direction thus tagging events involving strangeness production. By measuring the momenta of pions from two body weak decays using high resolution magnetic spectrometers one gains direct access to the ground state masses of the produced hyperfragments. At FAIR the PANDA Collaboration intends to produce double-hypernuclei by numbers with an antiproton beam and study their high resolution γ -spectroscopy thus providing for the first time precise information on the level structure of these nu…

Vertical Beam Polarization at MAMI

For the first time a vertically polarized electron beam has been used for physics experiments at MAMI in the energy range between 180 and 855 MeV. The beam-normal single-spin asymmetry $A_{\mathrm{n}}$, which is a direct probe of higher-order photon exchange beyond the first Born approximation, has been measured in the reaction $^{12}\mathrm C(\vec e,e')^{12}\mathrm C$. Vertical polarization orientation was necessary to measure this asymmetry with the existing experimental setup. In this paper we describe the procedure to orient the electron polarization vector vertically, and the concept of determining both its magnitude and orientation with the available setup. A sophisticated method has …

Multifocal adult rhabdomyoma of the head and neck: a case report and literature review.

Adult rhabdomyoma is a rare, usually solitary, primary tumour of striated muscle origin that almost exclusively presents in the head and neck region with predilection for male. We herein present a rare case of a multifocal adult rhabdomyoma in a 72-year-old woman. The lesions were located, the first one in the area of the left aryepiglottic fold and the second one right cervical arising from oesophagus. The diagnosis of the cervical mass was obtained prior to resection through cytological examination (FNAC). We discuss the clinical, cytological and histological findings and we provide a brief review of the literature on this entity.

Light sterile neutrino sensitivity at the nuSTORM facility

A facility that can deliver beams of electron and muon neutrinos from the decay of a stored muon beam has the potential to unambiguously resolve the issue of the evidence for light sterile neutrinos that arises in short-baseline neutrino oscillation experiments and from estimates of the effective number of neutrino flavors from fits to cosmological data. In this paper, we show that the nuSTORM facility, with stored muons of 3.8 GeV/c $\pm$ 10%, will be able to carry out a conclusive muon neutrino appearance search for sterile neutrinos and test the LSND and MiniBooNE experimental signals with 10$\sigma$ sensitivity, even assuming conservative estimates for the systematic uncertainties. This…

Performance of the large scale HV-CMOS pixel sensor MuPix8

The Mu3e experiment is searching for the charged lepton flavour violating decay $ ��^+\rightarrow e^+ e^- e^+ $, aiming for an ultimate sensitivity of one in $10^{16}$ decays. In an environment of up to $10^9$ muon decays per second the detector needs to provide precise vertex, time and momentum information to suppress accidental and physics background. The detector consists of cylindrical layers of $50\, ��\text{m}$ thin High Voltage Monolithic Active Pixel Sensors (HV-MAPS) placed in a $1\,\text{T}$ magnetic field. The measurement of the trajectories of the decay particles allows for a precise vertex and momentum reconstruction. Additional layers of fast scintillating fibre and tile detec…

MuPix8 — Large area monolithic HVCMOS pixel detector for the Mu3e experiment

Abstract The requirements of the ultra thin pixel detectors for the Mu3e experiment at PSI can be achieved by the HVCMOS technology, which allows the design of fast monolithic detectors. The latest nearly full size prototype, MuPix8, has a size of about 1 × 2 cm 2 . The pixel readout circuitry was fully redesigned in comparison to the previous MuPix versions. MuPix8’s readout electronics implement a new concept with two comparators and two different operation modes. One mode uses two threshold voltages for time walk correction, the other is a ramp-ADC. First tests show a detection efficiency of 99.6% for 4 GeV electrons.

First Measurement of the $Q^2$ Dependence of the Beam-Normal Single Spin Asymmetry for Elastic Scattering off Carbon

We report on the first Q^{2}-dependent measurement of the beam-normal single spin asymmetry A_{n} in the elastic scattering of 570 MeV vertically polarized electrons off ^{12}C. We cover the Q^{2} range between 0.02 and 0.05  GeV^{2}/c^{2} and determine A_{n} at four different Q^{2} values. The experimental results are compared to a theoretical calculation that relates A_{n} to the imaginary part of the two-photon exchange amplitude. The result emphasizes that the Q^{2} behavior of A_{n} given by the ratio of the Compton to charge form factors cannot be treated independently of the target nucleus.

Deuteron form factor measurements at low momentum transfers

A precise measurement of the elastic electron-deuteron scattering cross section at four-momentum transfers of 0.24 fm−1 ≤ Q ≤ 2.7 fm−1 has been performed at the Mainz Microtron. In this paper we describe the utilized experimental setup and the necessary analysis procedure to precisely determine the deuteron charge form factor from these data. Finally, the deuteron charge radius rd can be extracted from an extrapolation of that form factor to Q 2 = 0.

Beam-Recoil Polarization Measurement of π0 Electroproduction on the Proton in the Region of the Roper Resonance

The helicity-dependent recoil proton polarizations P_{x}^{'} and P_{z}^{'} as well as the helicity-independent component P_{y} have been measured in the p(e[over →],e^{'}p[over →])π^{0} reaction at four-momentum transfer Q^{2}≃0.1  GeV^{2}, center-of-mass proton emission angle θ_{p}^{*}≃90°, and invariant mass W≃1440  MeV. This first precise measurement of double-polarization observables in the energy domain of the Roper resonance P_{11}(1440) by exploiting recoil polarimetry has allowed for the extraction of its scalar electroexcitation amplitude at an unprecedentedly low value of Q^{2}, establishing a powerful instrument for probing the interplay of quark and meson degrees of freedom in t…

Initial state radiation experiment at MAMI

In an attempt to contribute further insight into the discrepancy between the Lamb shift and elastic scattering determinations of the proton charge radius, a new experiment at MAMI is underway, aimed at measuring proton form-factors at very low momentum transfers by using a new technique based on initial state radiation. This paper reports on the conclusions of the pilot measurement performed in 2010, whose main goal was to check the feasibility of the proposed experiment and to recognize and overcome any obstacles before running the full experiment. The modifications to the experimental apparatus are then explained which significantly improved the quality of data collected in the full scale…