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Search Results: 1 - 10 of 297484 matches for " J. Mammei "
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Low-Q scaling, duality, and the EMC effect
J. Arrington,R. Ent,C. E. Keppel,J. Mammei,I. Niculescu
Physics , 2003, DOI: 10.1103/PhysRevC.73.035205
Abstract: High energy lepton scattering has been the primary tool for mapping out the quark distributions of nucleons and nuclei. Data on the proton and deuteron have shown that there is a fundamental connection between the low and high energy regimes, referred to as quark-hadron duality. We present the results of similar studies to more carefully examine scaling, duality, and in particular the EMC effect in nuclei. We extract nuclear modifications to the structure function in the resonance region, and for the first time demonstrate that nuclear effects in the resonance region are identical to those measured in deep inelastic scattering. With the improved precision of the data at large $x$, we for the first time observe that the large-x crossover point appears to occur at lower $x$ values in carbon than in iron or gold.
The MOLLER Experiment
Juliette Mammei,for The MOLLER Collaboration
Physics , 2012, DOI: 10.1393/ncc/i2012-11284-7
Abstract: The MOLLER experiment will measure the weak charge of the electron, $Q^e_W = 1 - 4\sin^2\theta_W$, with a precision of 2.3% by measuring the parity-violating asymmetry in electron-electron (M\oller) scattering. This measurement will provide an ultra-precise measurement of the weak mixing angle, $\sin^2\theta_W$, which is on par with the two most precise collider measurements at the Z$^0$-pole. The precision of the experiment, with a fractional accuracy in the determination of $\sin^2\theta_W$ $\approx 0.1$%, makes it a probe of physics beyond the Standard Model with sensitivities to mass scales of new physics up to 7.5 TeV.
The Pb Radius Experiment (PREX)
Juliette Mammei,for the PREX Collaboration
Statistics , 2012, DOI: 10.1063/1.4826855
Abstract: We report the first measurement of the parity-violating asymmetry APV in the elastic scattering of polarized electrons from 208Pb from the Lead Radius Experiment PREX which ran in Hall A at the Thomas Jefferson National Accelerator Facility (JLab). APV is sensitive to the radius of the neutron distribution Rn. The Z boson that mediates the weak neutral interaction couples mainly to neutrons and provides a clean, model-independent measurement of the RMS radius Rn of the neutron distribution in the nucleus and is a fundamental test of nuclear structure theory. The result, APV = 0.656 +/- 0.060(stat) +/- 0.014(syst) ppm, corresponds to a difference between the radii of the neutron and proton distributions Rn - Rp = 0.33 +16 -18 fm and provides the first electroweak observation of the neutron skin which is expected in a heavy, neutron-rich nucleus.
Weak charge form factor and radius of 208Pb through parity violation in electron scattering
C. J. Horowitz,Z. Ahmed,C. -M. Jen,A. Rakhman,P. A. Souder,M. M. Dalton,N. Liyanage,K. D. Paschke,K. Saenboonruang,R. Silwal,G. B. Franklin,M. Friend,B. Quinn,K. S. Kumar,J. M. Mammei,D. McNulty,L. Mercado,S. Riordan,J. Wexler,R. W. Michaels,G. M. Urciuoli
Physics , 2012, DOI: 10.1103/PhysRevC.85.032501
Abstract: We use distorted wave electron scattering calculations to extract the weak charge form factor F_W(q), the weak charge radius R_W, and the point neutron radius R_n, of 208Pb from the PREX parity violating asymmetry measurement. The form factor is the Fourier transform of the weak charge density at the average momentum transfer q=0.475 fm$^{-1}$. We find F_W(q) =0.204 \pm 0.028 (exp) \pm 0.001 (model). We use the Helm model to infer the weak radius from F_W(q). We find R_W= 5.826 \pm 0.181 (exp) \pm 0.027 (model) fm. Here the exp error includes PREX statistical and systematic errors, while the model error describes the uncertainty in R_W from uncertainties in the surface thickness \sigma of the weak charge density. The weak radius is larger than the charge radius, implying a "weak charge skin" where the surface region is relatively enriched in weak charges compared to (electromagnetic) charges. We extract the point neutron radius R_n=5.751 \pm 0.175 (exp) \pm 0.026 (model) \pm 0.005 (strange) fm$, from R_W. Here there is only a very small error (strange) from possible strange quark contributions. We find R_n to be slightly smaller than R_W because of the nucleon's size. Finally, we find a neutron skin thickness of R_n-R_p=0.302\pm 0.175 (exp) \pm 0.026 (model) \pm 0.005 (strange) fm, where R_p is the point proton radius.
The proton and deuteron F_2 structure function at low Q^2
V. Tvaskis,J. Arrington,R. Asaturyan,O. K. Baker,H. P. Blok,P. Bosted,M. Boswell,A. Bruell,M. E. Christy,A. Cochran,R. Ent,B. W. Filippone,A. Gasparian,C. E. Keppel,E. Kinney,L. Lapikás,W. Lorenzon,D. J. Mack,J. Mammei,J. W. Martin,H. Mkrtchyan,I. Niculescu,R. B. Piercey,D. H. Potterveld,G. Smith,K. Spurlock,G. van der Steenhoven,S. Stepanyan,V. Tadevosian,S. A. Wood
Physics , 2010, DOI: 10.1103/PhysRevC.81.055207
Abstract: Measurements of the proton and deuteron $F_2$ structure functions are presented. The data, taken at Jefferson Lab Hall C, span the four-momentum transfer range $0.06 < Q^2 < 2.8$ GeV$^2$, and Bjorken $x$ values from 0.009 to 0.45, thus extending the knowledge of $F_2$ to low values of $Q^2$ at low $x$. Next-to-next-to-leading order calculations using recent parton distribution functions start to deviate from the data for $Q^2<2$ GeV$^2$ at the low and high $x$-values. Down to the lowest value of $Q^2$, the structure function is in good agreement with a parameterization of $F_2$ based on data that have been taken at much higher values of $Q^2$ or much lower values of $x$, and which is constrained by data at the photon point. The ratio of the deuteron and proton structure functions at low $x$ remains well described by a logarithmic dependence on $Q^2$ at low $Q^2$.
Determination of the Axial-Vector Weak Coupling Constant with Ultracold Neutrons
UCNA Collaboration,J. Liu,M. P. Mendenhall,A. T. Holley,H. O. Back,T. J. Bowles,L. J. Broussard,R. Carr,S. Clayton,S. Currie,B. W. Filippone,A. Garcia,P. Geltenbort,K. P. Hickerson,J. Hoagland,G. E. Hogan,B. Hona,T. M. Ito,C. -Y. Liu,M. Makela,R. R. Mammei,J. W. Martin,D. Melconian,C. L. Morris,R. W. Pattie Jr.,A. Perez Galvan,M. L. Pitt,B. Plaster,J. C. Ramsey,R. Rios,R. Russell,A. Saunders,S. J. Seestrom,W. E. Sondheim,E. Tatar,R. B. Vogelaar,B. VornDick,C. Wrede,H. Yan,A. R. Young
Physics , 2010, DOI: 10.1103/PhysRevLett.105.181803
Abstract: A precise measurement of the neutron decay $\beta$-asymmetry $A_0$ has been carried out using polarized ultracold neutrons (UCN) from the pulsed spallation UCN source at the Los Alamos Neutron Science Center (LANSCE). Combining data obtained in 2008 and 2009, we report $A_0 = -0.11966 \pm 0.00089_{-0.00140}^{+0.00123}$, from which we determine the ratio of the axial-vector to vector weak coupling of the nucleon $g_A/g_V = -1.27590_{-0.00445}^{+0.00409}$.
Precision Measurement of the Neutron Beta-Decay Asymmetry
M. P. Mendenhall,R. W. Pattie Jr,Y. Bagdasarova,D. B. Berguno,L. J. Broussard,R. Carr,S. Currie,X. Ding,B. W. Filippone,A. García,P. Geltenbort,K. P. Hickerson,J. Hoagland,A. T. Holley,R. Hong,T. M. Ito,A. Knecht,C. -Y. Liu,J. L. Liu,M. Makela,R. R. Mammei,J. W. Martin,D. Melconian,S. D. Moore,C. L. Morris,A. Pérez Galván,R. Picker,M. L. Pitt,B. Plaster,J. C. Ramsey,R. Rios,A. Saunders,S. J. Seestrom,E. I. Sharapov,W. E. Sondheim,E. Tatar,R. B. Vogelaar,B. VornDick,C. Wrede,A. R. Young,B. A. Zeck
Physics , 2012, DOI: 10.1103/PhysRevC.87.032501
Abstract: A new measurement of the neutron $\beta$-decay asymmetry $A_0$ has been carried out by the UCNA collaboration using polarized ultracold neutrons (UCN) from the solid deuterium UCN source at the Los Alamos Neutron Science Center (LANSCE). Improvements in the experiment have led to reductions in both statistical and systematic uncertainties leading to $A_0 = -0.11954(55)_{\rm stat.}(98)_{\rm syst.}$, corresponding to the ratio of axial-vector to vector coupling $\lambda \equiv g_A/g_V = -1.2756(30)$.
Large Magnetic Shielding Factor Measured by Nonlinear Magneto-optical Rotation
Jeffery W. Martin,Russell R. Mammei,Wolfgang Klassen,Cameron Cerasani,Taraneh Andalib,Christopher P. Bidinosti,Michael Lang,David Ostapchuk
Physics , 2014, DOI: 10.1016/j.nima.2015.01.003
Abstract: A passive magnetic shield was designed and constructed for magnetometer tests for the future neutron electric dipole moment experiment at TRIUMF. The axial shielding factor of the magnetic shield was measured using a magnetometer based on non-linear magneto-optical rotation of the plane of polarized laser light upon passage through a paraffin-coated vapour cell containing natural Rb at room temperature. The laser was tuned to the Rb D1 line, near the $^{85}$Rb $F=2\rightarrow 2,3$ transition. The shielding factor was measured by applying an axial field externally and measuring the magnetic field internally using the magnetometer. The axial shielding factor was determined to be $(1.3\pm 0.1)\times 10^{7}$, from an applied axial field of 1.45~$\mu$T in the background of Earth's magnetic field.
Search for a new gauge boson in the $A'$ Experiment (APEX)
S. Abrahamyan,Z. Ahmed,K. Allada,D. Anez,T. Averett,A. Barbieri,K. Bartlett,J. Beacham,J. Bono,J. R. Boyce,P. Brindza,A. Camsonne,K. Cranmer,M. M. Dalton,C. W. deJager,J. Donaghy,R. Essig,C. Field,E. Folts,A. Gasparian,N. Goeckner-Wald,J. Gomez,M. Graham,J. -O. Hansen,D. W. Higinbotham,T. Holmstrom,J. Huang,S. Iqbal,J. Jaros,E. Jensen,A. Kelleher,M. Khandaker,J. J. LeRose,R. Lindgren,N. Liyanage,E. Long,J. Mammei,P. Markowitz,T. Maruyama,V. Maxwell,S. Mayilyan,J. McDonald,R. Michaels,K. Moffeit,V. Nelyubin,A. Odian,M. Oriunno,R. Partridge,M. Paolone,E. Piasetzky,I. Pomerantz,Y. Qiang,S. Riordan,Y. Roblin,B. Sawatzky,P. Schuster,J. Segal,L. Selvy,A. Shahinyan,R. Subedi,V. Sulkosky,S. Stepanyan,N. Toro,D. Walz,B. Wojtsekhowski,J. Zhang
Physics , 2011, DOI: 10.1103/PhysRevLett.107.191804
Abstract: We present a search at Jefferson Laboratory for new forces mediated by sub-GeV vector bosons with weak coupling $\alpha'$ to electrons. Such a particle $A'$ can be produced in electron-nucleus fixed-target scattering and then decay to an $e^+e^-$ pair, producing a narrow resonance in the QED trident spectrum. Using APEX test run data, we searched in the mass range 175--250 MeV, found no evidence for an $A'\to e^+e^-$ reaction, and set an upper limit of $\alpha'/\alpha \simeq 10^{-6}$. Our findings demonstrate that fixed-target searches can explore a new, wide, and important range of masses and couplings for sub-GeV forces.
Measurement of the neutron $β$-asymmetry parameter $A_0$ with ultracold neutrons
UCNA Collaboration,B. Plaster,R. Rios,H. O. Back,T. J. Bowles,L. J. Broussard,R. Carr,S. Clayton,S. Currie,B. W. Filippone,A. Garcia,P. Geltenbort,K. P. Hickerson,J. Hoagland,G. E. Hogan,B. Hona,A. T. Holley,T. M. Ito,C. -Y. Liu,J. Liu,M. Makela,R. R. Mammei,J. W. Martin,D. Melconian,M. P. Mendenhall,C. L. Morris,R. Mortensen,R. W. Pattie, Jr.,A. Perez Galvan,M. L. Pitt,J. C. Ramsey,R. Russell,A. Saunders,R. Schmid,S. J. Seestrom,S. Sjue,W. E. Sondheim,E. Tatar,B. Tipton,R. B. Vogelaar,B. VornDick,C. Wrede,Y. P. Xu,H. Yan,A. R. Young,J. Yuan
Physics , 2012, DOI: 10.1103/PhysRevC.86.055501
Abstract: We present a detailed report of a measurement of the neutron $\beta$-asymmetry parameter $A_0$, the parity-violating angular correlation between the neutron spin and the decay electron momentum, performed with polarized ultracold neutrons (UCN). UCN were extracted from a pulsed spallation solid deuterium source and polarized via transport through a 7-T magnetic field. The polarized UCN were then transported through an adiabatic-fast-passage spin-flipper field region, prior to storage in a cylindrical decay volume situated within a 1-T $2 \times 2\pi$ solenoidal spectrometer. The asymmetry was extracted from measurements of the decay electrons in multiwire proportional chamber and plastic scintillator detector packages located on both ends of the spectrometer. From an analysis of data acquired during runs in 2008 and 2009, we report $A_0 = -0.11966 \pm 0.00089_{-0.00140} ^{+0.00123}$, from which we extract a value for the ratio of the weak axial-vector and vector coupling constants of the nucleon, $\lambda = g_A/g_V = -1.27590 \pm 0.00239_{-0.00377}^{+0.00331}$. Complete details of the analysis are presented.
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