-
R. Pohl,
F. Biraben,
C.A.N. Conde,
C. Donche Gay,
T.W. Hänsch,
F.J. Hartmann,
P. Hauser, V.W. Hughes,
O. Huot,
P. Indelicato, [......],
C. Petitjean,
P. Rabinowitz,
J.M.F. dos Santos,
L.A. Schaller,
H. Schneuwly,
W. Schott,
L.M. Simons,
D. Taqqu,
F. Trehin,
J.F.C.A. Veloso
[show abstract]
[hide abstract]
ABSTRACT: The contribution of the root mean square (RMS) proton charge radius to the Lamb shift (2S–2P energy difference) in muonic
hydrogen (μp) amounts to 2%. Apart from the uncertainty on this charge radius, theory predicts the Lamb shift with a precision
on the ppm level. We are going to measure ΔE (2 S1/2(F=1)–2 P3/2(F=2)) in a laser resonance experiment to a precision of 30 ppm (i.e., 10% of the natural linewidth) and to deduce the RMS
proton charge radius with 10−3 relative accuracy, 20 times more precise than presently known.
The most important requirement for the feasibility of such an experiment, namely the availability of a sufficient amount of
long lived metastable μp atoms in the 2S state, has been investigated in a recent experiment at PSI. Our analysis shows that
in the order of one percent of all muons stopped in low pressure hydrogen gas form a long lived μp(2S) with a lifetime of
the order of 1 μs.
The technical realization of our experiment involves a new high intensity low energy muon beam, an efficient low energy muon
entrance detector, a randomly triggered 3 stage laser system providing the 0.5 mJ, 7 ns laser pulses at 6.02 μm wavelength,
and a combination of a xenon gas proportional scintillation chamber (GPSC) and a microstrip gas chamber (MSGC) with a CsI
coated surface to detect the 2 keV X rays from theμp(2P → 1S) transition.
Hyperfine Interactions 04/2012; 127(1):161-166. · 0.21 Impact Factor
-
G W Bennett,
B Bousquet,
H N Brown,
G Bunce,
R M Carey,
P Cushman,
G.T. Danby,
P T Debevec,
M. Deile,
H Deng, [......],
A Steinmetz,
L. R. Sulak,
C Timmermans,
A Trofimov,
D Urner,
P von Walter,
D. Warburton,
D Winn,
A Yamamoto,
D Zimmerman
[show abstract]
[hide abstract]
ABSTRACT: Three independent searches for an electric dipole moment (EDM) of the positive and negative muons have been performed, using spin precession data from the muon g-2 storage ring at Brookhaven National Laboratory. Details on the experimental apparatus and the three analyses are presented. Since the individual results on the positive and negative muon, as well as the combined result, d=-0.1(0.9)E-19 e-cm, are all consistent with zero, we set a new muon EDM limit, |d| < 1.9E-19 e-cm (95% C.L.). This represents a factor of 5 improvement over the previous best limit on the muon EDM. Comment: 19 pages, 15 figures, 7 tables
11/2008;
-
G W Bennett,
B Bousquet,
H N Brown,
G Bunce,
R M Carey,
P Cushman,
G T Danby,
P T Debevec,
M Deile,
H Deng, [......],
A Steinmetz,
L R Sulak,
C Timmermans,
A Trofimov,
D Urner,
P von Walter,
D Warburton,
D Winn,
A Yamamoto,
D Zimmerman
[show abstract]
[hide abstract]
ABSTRACT: The spin precession frequency of muons stored in the (g-2) storage ring has been analyzed for evidence of Lorentz and CPT violation. Two Lorentz and CPT violation signatures were searched for a nonzero delta omega a(=omega a mu+ - omega a mu-) and a sidereal variation of omega a mu+/-). No significant effect is found, and the following limits on the standard-model extension parameters are obtained: bZ = -(1.0+/-1.1) x 10(-23) GeV; (m mu dZ0 + HXY)=(1.8+/-6.0) x 10(-23) GeV; and the 95% confidence level limits b perpendicular mu+ <1.4 x 10(-24) GeV and b perpendicular mu- <2.6 x 10(-24) GeV.
Physical Review Letters 03/2008; 100(9):091602. · 7.37 Impact Factor
-
H.-J. Mundinger,
K.-P. Arnold,
M. Gladisch,
J. Hofmann,
W. Jacobs,
H. Orth,
G. zu Putlitz,
J. Rosenkranz,
W. Schäfer,
W. Schwarz,
K. A. Woodle, V. W. Hughes
[show abstract]
[hide abstract]
ABSTRACT: Pionium (Pi), the Coulomb bound state of a positive pion π+ and an electron e−, has been formed with the beam-foil technique in vacuum with a total yield of 4.4(4) 10−5 per incoming pion. Neutral Pi was selected by a combined technique of magnetic sweeping and time-of-flight separation from the charged π+ beam. Pi was identified by the characteristic decay chain π+ → μ+νμ plus μ+ → e+νeμ and the velocity distribution of the slow pions and neutral Pi. This distribution was calculated with a Monte Carlo simulation and is in good agreement with the measurements.
EPL (Europhysics Letters) 07/2007; 8(4):339. · 2.17 Impact Factor
-
The CMD-2 Collaboration: R. R. Akhmetshin,
V. M. Aulchenko,
V. Sh. Banzarov,
L. M. Barkov,
N. S. Bashtovoy,
A. E. Bondar,
D. V. Bondarev,
A. V. Bragin,
S K Dhawan,
S. I. Eidelman, [......],
A. L. Sibidanov,
V. A. Sidorov,
A. N. Skrinsky,
V.P. Smakhtin,
I. G. Snopkov,
E P Solodov,
J. A. Thompson,
Yu. V. Yudin,
A. S. Zaitsev,
S. G. Zverev
[show abstract]
[hide abstract]
ABSTRACT: We present a measurement of the pion form factor based on e+e- annihilation data from the CMD-2 detector in the energy range 0.6<sqrt(s)<1.0 GeV with a systematic uncertainty of 0.8%. A data sample is five times larger than that used in our previous measurement.
11/2006;
-
R. R. Akhmetshin,
V. M. Aulchenko,
V. Sh. Banzarov,
L. M. Barkov,
N. S. Bashtovoy,
A. E. Bondar,
D. V. Bondarev,
A. V. Bragin,
S K Dhawan,
S. I. Eidelman, [......],
A. L. Sibidanov,
V. A. Sidorov,
A. N. Skrinsky,
V.P. Smakhtin,
I. G. Snopkov,
E P Solodov,
J. A. Thompson,
Yu. V. Yudin,
A. S. Zaitsev,
S. G. Zverev
[show abstract]
[hide abstract]
ABSTRACT: The cross section of the process e+e- -> pi+pi- has been measured at the CMD-2 detector in the 370-520 MeV center-of-mass (c.m.) energy range. A systematic uncertainty of the measurement is 0.7 %. Using all CMD-2 data on the pion form factor, the pion electromagnetic radius was calculated. The cross section of muon pair production was also determined.
11/2006;
-
G. W. Bennett,
B. Bousquet,
H. N. Brown,
G. Bunce,
R. M. Carey,
P. Cushman,
G. T. Danby,
P. T. Debevec,
M. Deile,
H. Deng, [......],
A. Steinmetz,
L. R. Sulak,
C. Timmermans,
A. Trofimov,
D. Urner,
P. von Walter,
D. Warburton,
D. Winn,
A. Yamamoto,
D. Zimmerman
[show abstract]
[hide abstract]
ABSTRACT: We present the final report from a series of precision measurements of the muon anomalous magnetic moment, aμ=(g-2)/2. The details of the experimental method, apparatus, data taking, and analysis are summarized. Data obtained at Brookhaven National Laboratory, using nearly equal samples of positive and negative muons, were used to deduce aμ(Expt)=11659208.0(5.4)(3.3)×10-10, where the statistical and systematic uncertainties are given, respectively. The combined uncertainty of 0.54 ppm represents a 14-fold improvement compared to previous measurements at CERN. The standard model value for aμ includes contributions from virtual QED, weak, and hadronic processes. While the QED processes account for most of the anomaly, the largest theoretical uncertainty, ≈0.55 ppm, is associated with first-order hadronic vacuum polarization. Present standard model evaluations, based on e+e- hadronic cross sections, lie 2.2–2.7 standard deviations below the experimental result.
Phys. Rev. D. 04/2006; 73(7).
-
V. M. Aul’chenko,
R. R. Akhmetshin,
V. Sh. Banzarov,
L. M. Barkov,
N. S. Bashtovoĭ,
D. V. Bondarev,
A. E. Bondar’,
A. V. Bragin,
N. I. Gabyshev,
D. A. Gorbachev, [......],
E. P. Solodov,
J. A. Thompson,
G. V. Fedotovich,
B. I. Khazin, V. W. Hughes,
A. G. Shamov,
Yu. M. Shatunov,
B. A. Shvarts,
S. I. Éĭdel’man,
Yu. V. Yudin
[show abstract]
[hide abstract]
ABSTRACT: The results of the experiment on the measurement of the e
+
e
− → π+π− cross section in a cm energy range of 370–520 MeV are presented. The systematic measurement error is equal to 0.7%. In the
vector dominance model, the pion electromagnetic radius is calculated using all the CMD-2 data on the pion form factor. The
cross section for the production of a muon pair is measured in the energy range of the experiment.
JETP Letters 01/2006; 84(8):413-417. · 1.35 Impact Factor
-
V. M. Aul’chenko,
R. R. Akhmetshin,
V. Sh. Banzarov,
L. M. Barkov,
N. S. Bashtovoi,
D. V. Bondarev,
A. E. Bondar’,
A. V. Bragin,
A. A. Valishev,
N. I. Gabyshev, [......],
E. P. Solodov,
J. A. Thompson,
G. V. Fedotovich,
B. I. Khazin, V. W. Hughes,
A. G. Shamov,
Yu. M. Shatunov,
B. A. Shwartz,
S. I. Éidel’man,
Yu. V. Yudin
[show abstract]
[hide abstract]
ABSTRACT: The cross section for the process e
+
e
− → π+π− is measured in the c.m. energy range 1.04—1.38 GeV by analyzing 995 000 selected collinear events including 860000 e
+
e
− events, 82000 μ+μ− events, and 33000 π+π− events. The systematic and statistical errors of measuring the pion form factor are equal to 1.2–4.2 and 5–13%, respectively.
JETP Letters 11/2005; 82(12):743-747. · 1.35 Impact Factor
-
B. Adeva,
E. Arik,
A. Arvidson,
B. Badełek,
G. Baum,
P. Berglund,
L. Betev,
R. Birsa,
N. de Botton,
F. Bradamante, [......],
J. Vogt,
R. Voss,
C. Whitten,
R. Windmolders,
R. Willumeit,
W. Wiślicki,
A. Witzmann,
A. M. Zanetti,
K. Zaremba,
J. Zhao
[show abstract]
[hide abstract]
ABSTRACT: We present a measurement of the longitudinal spin cross section asymmetry for deep-inelastic muon-nucleon interactions with two high transverse momentum hadrons in the final state. Two methods of event classification are used to increase the contribution of the photon-gluon fusion process to above 30%. The most effective one, based on a neural network approach, provides the asymmetries AplN⃗lhhX=0.030±0.057(stat)±0.010(syst) and AdlN⃗lhhX=0.070±0.076(stat)±0.010(syst). From these values we derive an averaged gluon polarization ΔG/G=-0.20±0.28(stat)±0.10(syst) at an average fraction of nucleon momentum carried by gluons 〈η〉=0.07.
Phys. Rev. D. 07/2004; 70(1).
-
M.N. Achasov,
R.R. Akhmetshin,
V.M. Aulchenko,
V.Sh. Banzarov,
A. Baratt,
L.M. Barkov,
S.E. Baru,
N.S. Bashtovoy,
K.I. Beloborodov,
A.V. Berdugin, [......],
A.N. Skrinsky,
I.G. Snopkov,
E.P. Solodov,
J.A. Thompson,
Y.V. Usov,
A.A. Valishev,
A.V. Vasiljev,
Y.V. Yudin,
A.S. Zaitsev,
S.G. Zverev
[show abstract]
[hide abstract]
ABSTRACT: The Cryogenic Magnetic Detector(CMD-2) and Spherical Neutral Detector(SND) operated at the VEPP-2M electron-positron collider in the c.m. energy range 360-1380MeV. The total integrated luminosity above 60pb–1 has been collected by both detectors. The cross sections of hadronic production have been measured with high precision. New results for the light vector meson parameters and rare decay mode were obtained.PACS: 13.66.Bc Hadron production in e–e+ interactions – 13.66.Jn Precision measurements in e–e+ interactions
European Physical Journal C 06/2004; 33:s583-s585. · 3.63 Impact Factor
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G W Bennett,
B Bousquet,
H N Brown,
G Bunce,
R M Carey,
P Cushman,
G T Danby,
P T Debevec,
M Deile,
H Deng, [......],
Y K Semertzidis,
P Shagin,
Yu M Shatunov,
E P Sichtermann,
E Solodov,
M Sossong,
L R Sulak,
A Trofimov,
P von Walter,
A Yamamoto
[show abstract]
[hide abstract]
ABSTRACT: The anomalous magnetic moment of the negative muon has been measured to a precision of 0.7 ppm (ppm) at the Brookhaven Alternating Gradient Synchrotron. This result is based on data collected in 2001, and is over an order of magnitude more precise than the previous measurement for the negative muon. The result a(mu(-))=11 659 214(8)(3) x 10(-10) (0.7 ppm), where the first uncertainty is statistical and the second is systematic, is consistent with previous measurements of the anomaly for the positive and the negative muon. The average of the measurements of the muon anomaly is a(mu)(exp)=11 659 208(6) x 10(-10) (0.5 ppm).
Physical Review Letters 05/2004; 92(16):161802. · 7.37 Impact Factor
-
S. I. Redin,
G. W. Bennett,
B. Bousquet,
H. N. Brown,
G. Bunce,
R. M. Carey,
P. Cushman,
G. T. Danby,
P. T. Debevec,
M. Deile, [......],
A. Steinmetz,
L. R. Sulak,
C. Timmermans,
A. Trofimov,
D. Urner,
P. von Walter,
D. Warburton,
D. Winn,
A. Yamamoto,
D. Zimmerman
[show abstract]
[hide abstract]
ABSTRACT: The measurement of the (g−2) value of leptons provides a unique test of theory since it is the only quantity (unlike charge
and mass) calculable in the framework of the Standard Model of elementary particles. The muon (g−2) experiment E821 is currently
in progress at Brookhaven National Laboratory. Four data taking runs for positive muons and one run for negative muons were
successfully accomplished in 1997–2000 and 2001, respectively. Results of the 1997–2000 runs have been published, thus completing
our experiment for μ+. Data analysis for the 2001 run for μ
− is currently in progress. To provide measurement of $a_\mu = \tfrac{1}
{2}(g - 2)_{\mu ^ - }$a_\mu = \tfrac{1}
{2}(g - 2)_{\mu ^ - } at the same level of accuracy as for $a_{\mu ^ + } = \tfrac{1}
{2}(g - 2)_{\mu ^ + }$a_{\mu ^ + } = \tfrac{1}
{2}(g - 2)_{\mu ^ + }, we need to have one more data taking run.
12/2003: pages 163-174;
-
S. Chekanov, M. Derrick, D. Krakauer, J. H. Loizides,
M. C. K. Mattingly,
P. Antonioli,
G. Bari,
M. Basile,
L. Bellagamba,
D. Boscherini,
A. Bruni,
G. Bruni,
G. Cara Romeo, [......],
S. Dhawan, V. W. Hughes,
P. B. Straub,
S. Bhadra,
C. D. Catterall,
S. Fourletov,
G. Hartner,
S. Menary,
M. Soares,
J. Standage
[show abstract]
[hide abstract]
ABSTRACT: A search for narrow-width resonances that decay into electron+jet or neutrino+jet has been performed with the ZEUS detector at the DESY ep collider HERA operating at center-of-mass energies of 300 and 318 GeV. An integrated e+p luminosity of 114.8pb-1 and e-p luminosity of 16.7pb-1 were used. No evidence for any resonance was found. Limits were derived on the Yukawa coupling λ as a function of the mass of a hypothetical resonance that has arbitrary decay branching ratios into eq or νq. These limits also apply to squarks predicted by R-parity-violating supersymmetry. Limits for the production of leptoquarks described by the Buchmüller-Rückl-Wyler model were also derived for masses up to 400 GeV. For λ=0.1, leptoquark masses up to 290 GeV are excluded.
Phys. Rev. D. 09/2003; 68(5).
-
R. R. Akhmetshin,
E. V. Anashkin,
A. B. Arbuzov,
V. Sh. Banzarov,
A. Baratt,
L. M. Barkov,
A. V. Bogdan,
A. E. Bondar,
D. V. Bondarev,
S. I. Eidelman, [......],
B. A. Shwartz,
A. L. Sibidanov,
V. A. Sidorov,
A. N. Skrinsky,
V.P. Smakhtin,
E P Solodov,
P. Yu. Stepanov,
J. A. Thompson,
A. S. Zaitsev,
for the CMD-2 Collaboration
[show abstract]
[hide abstract]
ABSTRACT: The updated results of the precise measurements of the processes e+e-->rho->pi+pi-, e+e-->omega->pi+pi-pi0 and e+e-->phi->KLKS performed by the CMD-2 collaboration are presented. The update appeared necessary due an overestimate of the integrated luminosity in previous analyses.
09/2003;
-
G W Bennett,
B Bousquet,
H N Brown,
G Bunce,
R M Carey,
P Cushman,
G T Danby,
P T Debevec,
M Deile,
H Deng, [......],
E P Sichtermann,
E Solodov,
M Sossong,
A Steinmetz,
L R Sulak,
A Trofimov,
D Urner,
P Von Walter,
D Warburton,
A Yamamoto
[show abstract]
[hide abstract]
ABSTRACT: A higher precision measurement of the anomalous g value, a(mu)=(g-2)/2, for the positive muon has been made at the Brookhaven Alternating Gradient Synchrotron, based on data collected in the year 2000. The result a(mu(+))=11 659 204(7)(5)x10(-10) (0.7 ppm) is in good agreement with previous measurements and has an error about one-half that of the combined previous data. The present world average experimental value is a(mu)(expt)=11 659 203(8)x10(-10) (0.7 ppm).
Physical Review Letters 10/2002; 89(10):101804. · 7.37 Impact Factor
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R. R. Akhmetshin,
E. V. Anashkin,
V. M. Aulchenko,
V. Sh. Banzarov,
L. M. Barkov,
S. E. Baru,
N. S. Bashtovoy,
A. E. Bondar,
D. V. Bondarev,
A. V. Bragin, [......],
V. P. Smakhtin,
I. G. Snopkov,
E. P. Solodov,
P. Yu. Stepanov,
A. I. Sukhanov,
J. A. Thompson,
V. M. Titov,
A. A. Valishev,
Yu. V. Yudin,
S. G. Zverev
[show abstract]
[hide abstract]
ABSTRACT: The Cryogenic Magnetic Detector (CMD‐2) and main it’s parameters are shortly described. The results for the cross sections of e+e− annihilation into hadrons are presented in the c.m. energy range from 0.37 to 1.39 GeV. The total integrated luminosity of about 31 pb−1 has been collected. The new results for the ρ and ω meson parameters were obtained. The pion form factor was determinated with a 0.6% systematic uncertainty. The major decay modes of the ϕ meson as well as multihadron final states have been studied in a broad energy range. © 2002 American Institute of Physics
AIP Conference Proceedings. 06/2002; 619(1):15-29.
-
L. K. Gladilin,
D. Hochman,
U. Karshon,
J. Breitweg,
D. Chapin,
R. Cross,
D. Kcira,
S. Lammers,
D. D. Reeder,
A. A. Savin, [......],
A. Deshpande,
S. Dhawan, V. W. Hughes,
P. B. Straub,
S. Bhadra,
C. D. Catterall,
S. Fourletov,
S. Menary,
M. Soares,
J. Standage
[show abstract]
[hide abstract]
ABSTRACT: The photon-proton total cross section has been measured in the process
e+ p -> e+ gamma p -> e+ X with the ZEUS detector at HERA. Events
were collected with photon virtuality Q^2 < 0.02 GeV^2 and average
gamma-p center-of-mass energy W_{gamma p} = 209 GeV in a dedicated run,
designed to control systematic effects, with an integrated luminosity of
49 nb^{-1}. The measured total cross section is sigma_{tot}^{gamma p} =
174 +- 1 (stat.) +- 13 (syst.) microbarns. The energy dependence of the
cross section is compatible with parameterizations of high-energy p-p
and p-pbar data.
Nuclear Physics B 03/2002; 627:3-28. · 4.66 Impact Factor
-
L. K. Gladilin,
D. Hochman,
U. Karshon,
J. Breitweg,
D. Chapin,
R. Cross,
D. Kcira,
S. Lammers,
D. D. Reeder,
A. A. Savin, [......],
A. Deshpande,
S. Dhawan, V. W. Hughes,
P. B. Straub,
S. Bhadra,
C. D. Catterall,
S. Fourletov,
S. Menary,
M. Soares,
J. Standage
[show abstract]
[hide abstract]
ABSTRACT: Dijet differential cross sections for the reaction e+p -> e+ + jet +
jet + X in the photoproduction regime have been measured with the ZEUS
detector at HERA using an integrated luminosity of 42.7 pb**{-1}. The
cross sections are given for photon-proton centre-of-mass energies in
the range 134< W <277 GeV. The differential cross sections as a
function of the dijet mass, Mjj, and of the dijet angular variables have
been measured for 47 < Mjj < 160 GeV and compared to
next-to-leading-order QCD calculations. The dijet events in the region
75< Mjj < 100 GeV have been used to derive a 95% C.L. upper limit
on the cross section for Z0 photoproduction of sigma(e+ p -> e+ Z0 X}
< 5.9 pb. Upper limits on the photoproduction of new heavy resonances
decaying into two jets are also presented for masses in the range
between 60 GeV and 155 GeV.
Physics Letters B 03/2002; 531:9-27. · 3.95 Impact Factor
-
S. Chekanov,
M. Derrick,
D. Krakauer,
S. Magill,
B. Musgrave,
A. Pellegrino,
J. Repond,
R. Yoshida,
M. C. K. Mattingly,
P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, [......],
W. H. Smith,
A. Deshpande,
S. Dhawan, V. W. Hughes,
P. B. Straub,
S. Bhadra,
C. D. Catterall,
W. R. Frisken,
M. Khakzad,
S. Menary
[show abstract]
[hide abstract]
ABSTRACT: Characteristics of the hadronic final state of diffractive deep inelastic scattering events ep⃗eXp were studied in the kinematic range 4<MX<35GeV, 4<Q2<150GeV2, 70<W<250GeV, and 0.0003<xP<0.03 with the ZEUS detector at the DESY ep collider HERA using an integrated luminosity of 13.8 pb-1. The events were tagged by identifying the diffractively scattered proton using the leading proton spectrometer. The properties of the hadronic final state X were studied in its center-of-mass frame using thrust, thrust angle, sphericity, energy flow, transverse energy flow, and “seagull” distributions. As the invariant mass of the system increases, the final state becomes more collimated, more aligned, and more asymmetric in the average transverse momentum with respect to the direction of the virtual photon. Comparisons of the properties of the hadronic final state with predictions from various Monte Carlo model generators suggest that the final state is dominated by qq̅ g states at the parton level.
Phys. Rev. D. 01/2002; 65(5).
