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Search Results: 1 - 10 of 138732 matches for " K. Aulenbacher "
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A surprising method for polarising antiprotons
Th. Walcher,H. Arenhoevel,K. Aulenbacher,R. Barday,A. Jankowiak
Physics , 2007, DOI: 10.1140/epja/i2008-10705-4
Abstract: We propose a method for polarising antiprotons in a storage ring by means of a polarised positron beam moving parallel to the antiprotons. If the relative velocity is adjusted to $v/c \approx 0.002$ the cross section for spin-flip is as large as about $2 \cdot 10^{13}$ barn as shown by new QED-calculations of the triple spin-cross sections. Two possibilities for providing a positron source with sufficient flux density are presented. A polarised positron beam with a polarisation of 0.70 and a flux density of approximately $1.5 \cdot 10^{10}$/(mm$^2$ s) appears to be feasible by means of a radioactive $^{11}$C dc-source. A more involved proposal is the production of polarised positrons by pair production with circularly polarised photons. It yields a polarisation of 0.76 and requires the injection into a small storage ring. Such polariser sources can be used at low (100 MeV) as well as at high (1 GeV) energy storage rings providing a time of about one hour for polarisation build-up of about $10^{10}$ antiprotons to a polarisation of about 0.18. A comparison with other proposals show a gain in the figure-of-merit by a factor of about ten.
Space Charge Expansion for Time-resolved Spin-Polarized Electron Spectroscopy
K. Aulenbacher,A. V. Subashiev,V. Tioukine,D. Bender,Yu. P. Yashin
Physics , 2004,
Abstract: Time resolved spin-polarized electron photoemission spectra are investigated as a function of excitation pulse energy for the heterostructures with a single strained layer and with a strained-well superlattice. At an average current exceeding 10 nA the emission pulse profiles are modified by the space charge pulse expansion during the electron transport to detector. The pulse expansion enables the separation of electrons that have spent minimum time in the sample. For the superlattice structure these electrons showed maximum polarization above 90 %. Variation in the pulse profiles for the two structures is interpreted as resulting from the difference in the effective NEA values.
An effective method for polarising antiprotons
Th. Walcher,H. Arenh?vel,K. Aulenbacher,R. Barday,A. Jankowiak
Physics , 2006,
Abstract: There exists an inconsistency in the value of the kinetic energies of the antiproton in the electron laboratory reference frame and of the electron in the antiproton laboratory reference frame taken wrongly both as 0.65 keV (see figure 1 and table 2) of the paper. The consequence of this mistake is that the relative velocity of the electron is not -0.0504 (see table 2) but -0.00118, i.e. a factor of \sqrt{m_{electron}/m_{proton}} = 1/43 smaller. The consequence of this factor is that the relative velocity \beta_{relative} in eq. (27) and \kappa are smaller by this factor. This means that the time for polarisation build-up is longer by a factor 43. Though the principle idea is not put into question, the method is not effective "with todays technology" and we have to withdraw the paper and the proposal.
Measurement of Strange Quark Contributions to the Nucleon's Form Factors at Q^2=0.230 (GeV/c)^2
A4 Collaboration,F. E. Maas,P. Achenbach,K. Aulenbacher,S. Baunack,L. Capozza,J. Diefenbach,K. Grimm,Y. Imai,T. Hammel,D. von Harrach,E. -M. Kabuss,R. Kothe,J. H. Lee,A. Lorente,A. Lopes Ginja,L. Nungesser,E. Schilling,G. Stephan,C. Weinrich,I. Altarev,J. Arvieux,B. Collin,R. Frascaria,M. Guidal,R. Kunne,D. Marchand,M. Morlet,S. Ong,J. van de Wiele,S. Kowalski,B. Plaster,R. Suleiman,S. Taylor
Physics , 2004, DOI: 10.1103/PhysRevLett.93.022002
Abstract: We report on a measurement of the parity-violating asymmetry in the scattering of longitudinally polarized electrons on unpolarized protons at a $Q^2$ of 0.230 (GeV/c)^2 and a scattering angle of \theta_e = 30^o - 40^o. Using a large acceptance fast PbF_2 calorimeter with a solid angle of \Delta\Omega = 0.62 sr the A4 experiment is the first parity violation experiment to count individual scattering events. The measured asymmetry is A_{phys} =(-5.44 +- 0.54_{stat} +- 0.27_{\rm sys}) 10^{-6}. The Standard Model expectation assuming no strangeness contributions to the vector form factors is $A_0=(-6.30 +- 0.43) 10^{-6}$. The difference is a direct measurement of the strangeness contribution to the vector form factors of the proton. The extracted value is G^s_E + 0.225 G^s_M = 0.039 +- 0.034 or F^s_1 + 0.130 F^s_2 = 0.032 +- 0.028.
Sidebands in Optically Detected Magnetic Resonance Signals of Nitrogen Vacancy Centers in Diamond
Maria Simanovskaia,Kasper Jensen,Andrey Jarmola,Kurt Aulenbacher,Neil Manson,Dmitry Budker
Physics , 2012, DOI: 10.1103/PhysRevB.87.224106
Abstract: We study features in the optically detected magnetic resonance (ODMR) signals associated with negatively charged nitrogen-vacancy (NV) centers coupled to other paramagnetic impurities in diamond. Our results are important for understanding ODMR line shapes and for optimization of devices based on NV centers. We determine the origins of several side features to the unperturbed NV magnetic resonance by studying their magnetic field and microwave power dependences. Side resonances separated by around 130 MHz are due to hyperfine coupling between NV centers and nearest-neighbor C-13 nuclear spins. Side resonances separated by approximately {40, 260, 300} MHz are found to originate from simultaneous spin flipping of NV centers and single substitutional nitrogen atoms. All results are in agreement with the presented theoretical calculations.
Measurement of the Transverse Beam Spin Asymmetry in Elastic Electron Proton Scattering and the Inelastic Contribution to the Imaginary Part of the Two-Photon Exchange Amplitude
F. E. Maas,K. Aulenbacher,S. Baunack,L. Capozza,J. Diefenbach,B. Gl?ser,Y. Imai,T. Hammel,D. von Harrach,E. -M. Kabub,R. Kothe,J. H. Lee,A. Sanchez-Lorente,E. Schilling,D. Schwaab,G. Stephan,G. Weber,C. Weinrich,I. Altarev,J. Arvieux,M. Elyakoubi,R. Frascaria,R. Kunne,M. Morlet,S. Ong,J. Vandewiele,S. Kowalski,R. Suleiman,S. Taylor
Physics , 2004, DOI: 10.1103/PhysRevLett.94.082001
Abstract: We report on a measurement of the asymmetry in the scattering of transversely polarized electrons off unpolarized protons, A$_\perp$, at two Q$^2$ values of \qsquaredaveragedlow (GeV/c)$^2$ and \qsquaredaveragedhighII (GeV/c)$^2$ and a scattering angle of $30^\circ < \theta_e < 40^\circ$. The measured transverse asymmetries are A$_{\perp}$(Q$^2$ = \qsquaredaveragedlow (GeV/c)$^2$) = (\experimentalasymmetry alulowcorr $\pm$ \statisticalerrorlow$_{\rm stat}$ $\pm$ \combinedsyspolerrorlowalucor$_{\rm sys}$) $\times$ 10$^{-6}$ and A$_{\perp}$(Q$^2$ = \qsquaredaveragedhighII (GeV/c)$^2$) = (\experimentalasymme tryaluhighcorr $\pm$ \statisticalerrorhigh$_{\rm stat}$ $\pm$ \combinedsyspolerrorhighalucor$_{\rm sys}$) $\times$ 10$^{-6}$. The first errors denotes the statistical error and the second the systematic uncertainties. A$_\perp$ arises from the imaginary part of the two-photon exchange amplitude and is zero in the one-photon exchange approximation. From comparison with theoretical estimates of A$_\perp$ we conclude that $\pi$N-intermediate states give a substantial contribution to the imaginary part of the two-photon amplitude. The contribution from the ground state proton to the imaginary part of the two-photon exchange can be neglected. There is no obvious reason why this should be different for the real part of the two-photon amplitude, which enters into the radiative corrections for the Rosenbluth separation measurements of the electric form factor of the proton.
Measurement of Strange Quark Contributions to the Vector Form Factors of the Proton at Q**2=0.22 (GeV/c)**2
S. Baunack,K. Aulenbacher,D. Balaguer Ríos,L. Capozza,J. Diefenbach,B. Gl?ser,D. v. Harrach,Y. Imai,E. M. Kabu?,R. Kothe,J. H. Lee,H. Merkel,M. C. Mora Espí,U. Müller,E. Schilling,G. Stephan,C. Weinrich,J. Arvieux,M. A. El-Yakoubi,R. Kunne,F. E. Maas,M. Morlet,S. Ong,J. van de Wiele,S. Kowalski,Y. Prok,S. Taylor
Physics , 2009, DOI: 10.1103/PhysRevLett.102.151803
Abstract: A new measurement of the parity violating asymmetry in elastic electron scattering on hydrogen at backward angles and at a four momentum transfer of Q^2=0.22 (GeV/c)^2 is reported here. The measured asymmetry is A_LR=(-17.23 +- 0.82_stat +-0.89_syst) ppm. The Standard Model prediction assuming no strangeness is A_0=(-15.87 +- 1.22) ppm. In combination with previous results from measurements at forward angles, it it possible to disentangle for the first time the strange electric and magnetic form factors at this momentum transfer, G_E^s(0.22)=0.050 +- 0.038 +- 0.019 and G_M^s(0.22)=-0.14 +- 0.11 +- 0.11.
Evidence for Strange Quark Contributions to the Nucleon's Form Factors at $Q^2$ = 0.108 (GeV/c)$^2$
F. E. Maas,K. Aulenbacher,S. Baunack,L. Capozza,J. Diefenbach,B. Gl?ser,T. Hammel,D. von Harrach,Y. Imai,E. -M. Kabu?,R. Kothe,J. H. Lee,A. Lorente,E. Schilling,D. Schwaab,M. Sikora,G. Stephan,G. Weber,C. Weinrich,I. Altarev,J. Arvieux,M. El-Yakoubi,R. Frascaria,R. Kunne,M. Morlet,S. Ong,J. van de Wiele,S. Kowalski,B. Plaster,R. Suleiman,S. Taylor
Physics , 2004, DOI: 10.1103/PhysRevLett.94.152001
Abstract: We report on a measurement of the parity violating asymmetry in the elastic scattering of polarized electrons off unpolarized protons with the A4 apparatus at MAMI in Mainz at a four momentum transfer value of $Q^2$ = \Qsquare (GeV/c)$^2$ and at a forward electron scattering angle of 30$^\circ < \theta_e < 40^\circ$. The measured asymmetry is $A_{LR}(\vec{e}p)$ = (\Aphys $\pm$ \Deltastat$_{stat}$ $\pm$ \Deltasyst$_{syst}$) $\times$ 10$^{-6}$. The expectation from the Standard Model assuming no strangeness contribution to the vector current is A$_0$ = (\Azero $\pm$ \DeltaAzero) $\times$ 10$^{-6}$. We have improved the statistical accuracy by a factor of 3 as compared to our previous measurements at a higher $Q^2$. We have extracted the strangeness contribution to the electromagnetic form factors from our data to be $G_E^s$ + \FakGMs $G_M^s$ = \GEsGMs $\pm $ \DeltaGEsGMs at $Q^2$ = \Qsquare (GeV/c)$^2$. As in our previous measurement at higher momentum transfer for $G_E^s$ + 0.230 $G_M^s$, we again find the value for $G_E^s$ + \FakGMs $G_M^s$ to be positive, this time at an improved significance level of 2 $\sigma$.
Measuring the weak mixing angle with the P2 experiment at MESA
Niklaus Berger,Kurt Aulenbacher,Sebastian Baunack,Dominik Becker,Jürgen Diefenbach,Michael Gericke,Kathrin Gerz,Ruth Herbertz,Krishna Kumar,Frank Maas,Matthias Molitor,David Rodríguez Pi?eiro,Iurii Sorokin,Paul Souder,Hubert Spiesberger,Alexey Tyukin,Valery Tyukin,Marco Zimmermann
Physics , 2015,
Abstract: The P2 experiment in Mainz aims to measure the weak mixing angle in electron- proton scattering to a precision of 0.13 %. In order to suppress uncertainties due to proton structure and contributions from box graphs, both a low average momentum transfer $Q^2$ of $4.5\cdot 10^{-3}$ GeV$^2/c^2$ and a low beam energy of 155 MeV are chosen. In order to collect the enormous statistics required for this measurement, the new Mainz Energy Recovery Superconducting Accelerator (MESA) is being constructed. These proceedings describe the motivation for the measurement, the experimental and accelerator challenges and how we plan to tackle them.
The MOLLER Experiment: An Ultra-Precise Measurement of the Weak Mixing Angle Using M?ller Scattering
MOLLER Collaboration,J. Benesch,P. Brindza,R. D. Carlini,J-P. Chen,E. Chudakov,S. Covrig,M. M. Dalton,A. Deur,D. Gaskell,A. Gavalya,J. Gomez,D. W. Higinbotham,C. Keppel,D. Meekins,R. Michaels,B. Moffit,Y. Roblin,R. Suleiman,R. Wines,B. Wojtsekhowski,G. Cates,D. Crabb,D. Day,K. Gnanvo,D. Keller,N. Liyanage,V. V. Nelyubin,H. Nguyen,B. Norum,K. Paschke,V. Sulkosky,J. Zhang,X. Zheng,J. Birchall,P. Blunden,M. T. W. Gericke,W. R. Falk,L. Lee,J. Mammei,S. A. Page,W. T. H. van Oers,K. Dehmelt,A. Deshpande,N. Feege,T. K. Hemmick,K. S. Kumar,T. Kutz,R. Miskimen,M. J. Ramsey-Musolf,S. Riordan,N. Hirlinger Saylor,J. Bessuille,E. Ihloff,J. Kelsey,S. Kowalski,R. Silwal,G. De Cataldo,R. De Leo,D. Di Bari,L. Lagamba,E. NappiV. Bellini,F. Mammoliti,F. Noto,M. L. Sperduto,C. M. Sutera,P. Cole,T. A. Forest,M. Khandekar,D. McNulty,K. Aulenbacher,S. Baunack,F. Maas,V. Tioukine,R. Gilman,K. Myers,R. Ransome,A. Tadepalli,R. Beniniwattha,R. Holmes,P. Souder,D. S. Armstrong,T. D. Averett,W. Deconinck,W. Duvall,A. Lee,M. L. Pitt,J. A. Dunne,D. Dutta,L. El Fassi,F. De Persio,F. Meddi,G. M. Urciuoli,E. Cisbani,C. Fanelli,F. Garibaldi,K. Johnston,N. Simicevic,S. Wells,P. M. King,J. Roche,J. Arrington,P. E. Reimer,G. Franklin,B. Quinn,A. Ahmidouch,S. Danagoulian,O. Glamazdin,R. Pomatsalyuk,R. Mammei,J. W. Martin,T. Holmstrom,J. Erler,Yu. G. Kolomensky,J. Napolitano,K. A. Aniol,W. D. Ramsay,E. Korkmaz,D. T. Spayde,F. Benmokhtar,A. Del Dotto,R. Perrino,S. Barkanova,A. Aleksejevs,J. Singh
Physics , 2014,
Abstract: The physics case and an experimental overview of the MOLLER (Measurement Of a Lepton Lepton Electroweak Reaction) experiment at the 12 GeV upgraded Jefferson Lab are presented. A highlight of the Fundamental Symmetries subfield of the 2007 NSAC Long Range Plan was the SLAC E158 measurement of the parity-violating asymmetry $A_{PV}$ in polarized electron-electron (M{\o}ller) scattering. The proposed MOLLER experiment will improve on this result by a factor of five, yielding the most precise measurement of the weak mixing angle at low or high energy anticipated over the next decade. This new result would be sensitive to the interference of the electromagnetic amplitude with new neutral current amplitudes as weak as $\sim 10^{-3}\cdot G_F$ from as yet undiscovered dynamics beyond the Standard Model. The resulting discovery reach is unmatched by any proposed experiment measuring a flavor- and CP-conserving process over the next decade, and yields a unique window to new physics at MeV and multi-TeV scales, complementary to direct searches at high energy colliders such as the Large Hadron Collider (LHC). The experiment takes advantage of the unique opportunity provided by the upgraded electron beam energy, luminosity, and stability at Jefferson Laboratory and the extensive experience accumulated in the community after a round of recent successfully completed parity-violating electron scattering experiments
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