-
V. V. Barmin,
A. E. Asratyan,
V. S. Borisov,
C. Curceanu,
G. V. Davidenko,
A. G. Dolgolenko,
C. Guaraldo, M. A. Kubantsev,
I. F. Larin,
V. A. Matveev,
V. A. Shebanov,
N. N. Shishov,
L. I. Sokolov,
G. K. Tumanov,
V. S. Verebryusov,
DIANA Collaboration
[show abstract]
[hide abstract]
ABSTRACT: The data on the charge-exchange reaction K
+Xe → K
0
pXe′, obtained with the bubble chamber DIANA, are reanalyzed using increased statistics and updated selections. Our previous
evidence for formation of a narrow pK
0 resonance with mass near 1538 MeV is confirmed. The statistical significance of the signal reaches some 8 (6) standard deviations
when estimated as $
{S \mathord{\left/
{\vphantom {S {\sqrt B \left( {{S \mathord{\left/
{\vphantom {S {\sqrt {B + S} }}} \right.
\kern-\nulldelimiterspace} {\sqrt {B + S} }}} \right)}}} \right.
\kern-\nulldelimiterspace} {\sqrt B \left( {{S \mathord{\left/
{\vphantom {S {\sqrt {B + S} }}} \right.
\kern-\nulldelimiterspace} {\sqrt {B + S} }}} \right)}}
$
{S \mathord{\left/
{\vphantom {S {\sqrt B \left( {{S \mathord{\left/
{\vphantom {S {\sqrt {B + S} }}} \right.
\kern-\nulldelimiterspace} {\sqrt {B + S} }}} \right)}}} \right.
\kern-\nulldelimiterspace} {\sqrt B \left( {{S \mathord{\left/
{\vphantom {S {\sqrt {B + S} }}} \right.
\kern-\nulldelimiterspace} {\sqrt {B + S} }}} \right)}}
. The mass and intrinsic width of the Θ+ baryon are measured as m = 1538 ± 2 MeV and Γ = 0.39 ± 0.10 MeV.
Physics of Atomic Nuclei 04/2012; 73(7):1168-1175. · 0.57 Impact Factor
-
The SELEX Collaboration,
A. Blanco-Covarrubias,
J. Engelfried,
U. Akgun,
G. Alkhazov,
J. Amaro-Reyes,
A. G. Atamantchouk,
A. S. Ayan,
M. Y. Balatz,
N. F. Bondar, [......],
A. N. Vasiliev,
D. V. Vavilov,
E. Vázquez-Jáuregui,
V. S. Verebryusov,
V. A. Victorov,
V. E. Vishnyakov,
A. A. Vorobyov,
K. Vorwalter,
J. You,
R. Zukanovich-Funchal
[show abstract]
[hide abstract]
ABSTRACT: Using data taken by SELEX during the 1996–1997 fixed target run at Fermilab, we study the production of charmed hadrons on
copper and carbon targets withΣ
−, p, π
−, and π
+ beams. Parametrizing the dependence of the inclusive production cross section on the atomic number A as A
α
, we determine α forD
+, D
0, D
s
+, D
+(2010), Λ
c
+, and their respective anti-particles, as a function of their transverse momentum p
t
and scaled longitudinal momentumx
F
. Within our statistics there is no dependence of α on x
F
for any charm species for the interval 0.1<x
F
<1.0. The average value of α for charm production by pion beams is α
meson=0.850±0.028. This is somewhat larger than the corresponding average α
baryon=0.755±0.016 for charm production by baryon beams (Σ
−, p).
PACS13.85.Ni-14.65.Dw-24.85.+p
European Physical Journal C 04/2012; 64(4):637-644. · 3.63 Impact Factor
-
V. V. Barmin,
A E Asratyan,
V. S. Borisov,
C. Curceanu,
G. V. Davidenko,
A. G. Dolgolenko,
C Guaraldo, M A Kubantsev,
I. F. Larin,
V. A. Matveev,
V. A. Shebanov,
N. N. Shishov,
L. I. Sokolov,
G. K. Tumanov,
V. S. Verebryusov
[show abstract]
[hide abstract]
ABSTRACT: The data on the reactions K^+Xe --> K^0 \gamma X and K^+Xe --> K^+ \gamma X, obtained with the bubble chamber DIANA, have been analyzed for possible radiative decays of the \Theta^+(1540) baryon: \Theta^+ --> K^0 p \gamma and \Theta^+ --> K^+ n \gamma. No signals have been observed, and we derive the upper limits \Gamma(\Theta^+ --> K^0 p \gamma) / \Gamma(\Theta^+ --> K^0 p) < 0.032 and \Gamma(\Theta^+ --> K^+ n \gamma) / \Gamma(\Theta^+ --> K^+ n) < 0.041 which, using our previous measurement of \Gamma(\Theta^+ --> KN) = (0.39+-0.10) MeV, translate to \Gamma(\Theta^+ --> K^0 p \gamma) < 8 keV and \Gamma(\Theta^+ --> K^+ n \gamma) < 11 keV at 90% confidence level. We have also measured the cross sections of K^+ -induced reactions involving emission of a neutral pion: \sigma(K^+n --> K^0 p \pi^0) = (68+-18) \mub and \sigma(K^+N --> K^+ N \pi^0) = (30+-8) \mub for incident K^+ momentum of 640 MeV. Comment: 8 pages
09/2009;
-
Selex Collaboration,
E. Vázquez-Jáuregui,
J. Engelfried,
U. Akgun,
G. Alkhazov,
J. Amaro-Reyes,
A. G. Atamantchouk,
A. S. Ayan,
M. Y. Balatz,
A. Blanco-Covarrubias, [......],
D. V. Vavilov,
V. S. Verebryusov,
V. A. Victorov,
V. E. Vishnyakov,
A. A. Vorobyov,
K. Vorwalter,
J. You,
Wenheng Zhao,
Shuchen Zheng,
R. Zukanovich-Funchal
[show abstract]
[hide abstract]
ABSTRACT: We report the first observation of two Cabibbo-suppressed decay modes,
Ξc+→Σππ and
Ξc+→Σππ. We observe
59±14 over a background of 87, and 22±8 over a background
of 13 events, respectively, for the signals. The data were accumulated
using the SELEX spectrometer during the 1996 1997 fixed target run at
Fermilab, chiefly from a 600GeV/cΣ beam. The branching
ratios of the decays relative to the Cabibbo-favored
Ξc+→Ξππ are measured
to be
B(Ξc+→Σππ)/B(Ξc+→Ξππ)=0.48±0.20,
and
B(Ξc+→Σππ)/B(Ξc+→Ξππ)=0.18±0.09,
respectively. We also report branching ratios for the same decay modes
of the Λc+ relative to
Λc+→pKπ.
Physics Letters B 08/2008; 666:299-304. · 3.95 Impact Factor
-
V. V. Barmin,
A. E. Asratyan,
V. S. Borisov,
C. Curceanu,
G. V. Davidenko,
A. G. Dolgolenko,
C. Guaraldo, M. A. Kubantsev,
I. F. Larin,
V. A. Matveev,
V. A. Shebanov,
N. N. Shishov,
L. I. Sokolov,
G. K. Tumanov
[show abstract]
[hide abstract]
ABSTRACT: We have continued our investigation of the charge-exchange reaction K
+Xe → K
0
pXe’ in the bubble chamber DIANA. In agreement with our previous results based on part of the present statistics, formation
of a narrow pK
0 resonance with mass of 1537 ± 2 MeV/c
2 is observed in the elementary transition K
+
n → K
0
p on a neutron bound in the xenon nucleus. The visible width of the peak is consistent with being entirely due to instrumental
resolution and allows one to place an upper limit on its intrinsic width: Γ < 9 MeV/c
2. A more precise estimate of the resonance intrinsic width, Γ = 0.36 ± 0.11 MeV/c
2, is obtained from the ratio between the numbers of resonant and nonresonant charge-exchange events. The signal is observed
in a restricted interval of incident K
+ momentum that is consistent with smearing of a narrow pK
0 resonance by Fermi motion of the target neutron. The statistical significance of the signal is some 7.3, 5.3, and 4.3 standard
deviations for the estimators
S/ÖB ,S/Ö{S + B}S/\sqrt B ,S/\sqrt {S + B}
and
S/Ö{S + 2B}S/\sqrt {S + 2B}
, respectively. This observation confirms and reinforces our earlier results, and offers strong evidence for formation of
a pentaquark baryon with positive strangeness in the charge-exchange reaction K
+
n → K
0
p on a bound neutron.
Physics of Atomic Nuclei 12/2006; 70(1):35-43. · 0.57 Impact Factor
-
A V Evdokimov,
U Akgun,
G Alkhazov,
J Amaro-Reyes,
A G Atamantchouk,
A S Ayan,
M Y Balatz,
N F Bondar,
P S Cooper,
L J Dauwe, [......],
E Vázquez-Jáuregui,
V S Verebryusov,
V A Victorov,
V E Vishnyakov,
A A Vorobyov,
K Vorwalter,
J You,
Zhao Wenheng,
Zheng Shuchen,
R Zukanovich-Funchal
[show abstract]
[hide abstract]
ABSTRACT: We report the first observation of a charm-strange meson D(+)(sJ)(2632) at a mass of 2632.5+/-1.7 MeV/c(2) in data from SELEX, the charm hadro-production experiment E781 at Fermilab. This state is seen in two decay modes, D(+)(s)eta and D0K+. In the D(+)(s)eta decay mode we observe a peak with 101 events over a combinatoric background of 54.9 events at a mass of 2635.4+/-3.3 MeV/c(2). There is a corresponding peak of 21 events over a background of 6.9 at 2631.5+/-2.0 MeV/c(2) in the decay mode D0K+. The decay width of this state is <17 MeV/c(2) at 90% confidence level. The relative branching ratio Gamma(D0K+)/Gamma(D(+)(s)eta) is 0.14+/-0.06. The mechanism that keeps this state narrow is unclear. Its decay pattern is also unusual, being dominated by the D(+)(s)eta decay mode.
Physical Review Letters 12/2004; 93(24):242001. · 7.37 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A narrow baryon resonance is observed in the invariant mass of the K
S
0
p system formed in neutrino and antineutrino collisions with nuclei. The mass of the resonance is estimated at 1533±5 MeV.
The observed width is less than 20 MeV and is compatible with being entirely due to experimental resolution. The statistical
significance of the signal is near 6.7 standard deviations. Since the position of the observed resonance does not match the
mass of any known Σ*+ states, we believe that it arises from the neutrino production of the Θ+ pentaquark baryon. The analysis is based on the data obtained in past neutrino experiments with big bubble chambers: WA21,
WA25, WA59, E180, and E632.
Physics of Atomic Nuclei 03/2004; 67(4):682-687. · 0.57 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A narrow baryon resonance is observed in invariant mass of the pKshort system formed in neutrino and antineutrino collisions with nuclei. The mass of the resonance is estimated as (1533+-5)MeV. The observed width is less than 20 MeV, and is compatible with being entirely due to experimental resolution. The statistical significance of the signal is near 6.7 standard deviations. As the position of the observed resonance does not match the mass of any known \Sigma^{*+} state, we believe that it arises from neutrino production of the \Theta^+ pentaquark baryon. The analysis is based on the data obtained in past neutrino experiments with big bubble chambers: WA21, WA25, WA59, E180 and E632.
10/2003;
-
[show abstract]
[hide abstract]
ABSTRACT: Multi-ring signatures of
ne\nu_e
appearance via the oscillation
nm ® ne\nu_\mu \rightarrow \nu_e
are formulated for a water Cherenkov detector. These signatures are appropriate for long-baseline neutrino experiments operating at relatively high neutrino energies
$E_\nu > 2$E_\nu > 2
GeV that emphasize the matter effect. The NC background is less for selected multi-ring events than for 1e-like events, and may be directly estimated from the data. Our results suggest that best sensitivity to
sin2 2q13\sin^2 2\theta_{13}
and to the sign of
Dm231\Delta m^2_{31}
can be reached with baselines over some 6000 km.
European Physical Journal C 09/2003; 31(1):31-36. · 3.63 Impact Factor
-
M Mattson,
G Alkhazov,
A G Atamantchouk,
M Y Balatz,
N F Bondar,
P S Cooper,
L J Dauwe,
G V Davidenko,
U Dersch,
A G Dolgolenko, [......],
D V Vavilov,
V S Verebryusov,
V A Victorov,
V E Vishnyakov,
A A Vorobyov,
K Vorwalter,
J You,
Zhao Wenheng,
Zheng Shuchen,
R Zukanovich-Funchal
[show abstract]
[hide abstract]
ABSTRACT: We observe a signal for the doubly charmed baryon Xi(+)(cc) in the charged decay mode Xi(+)(cc)-->Lambda(+)(c)K-pi(+) in data from SELEX, the charm hadroproduction experiment at Fermilab. We observe an excess of 15.9 events over an expected background of 6.1+/-0.5 events, a statistical significance of 6.3sigma. The observed mass of this state is 3519+/-1 MeV/c(2). The Gaussian mass width of this state is 3 MeV/c(2), consistent with resolution; its lifetime is less than 33 fs at 90% confidence.
Physical Review Letters 09/2002; 89(11):112001. · 7.37 Impact Factor
-
SELEX Collaboration,
F. G. Garcia,
G. Alkhazov,
A. G. Atamantchouk,
M. Y. Balatz,
N. F. Bondar,
P. S. Cooper,
L. J. Dauwe,
G. V. Davidenko,
U. Dersch, [......],
D. V. Vavilov,
V. S. Verebryusov,
V. A. Victorov,
V. E. Vishnyakov,
A. A. Vorobyov,
K. Vorwalter,
J. You,
Wenheng Zhao,
Shuchen Zheng,
R. Zukanovich-Funchal
[show abstract]
[hide abstract]
ABSTRACT: We present data from Fermilab experiment E781 (SELEX) on the
hadroproduction asymmetry for Λ¯c-
compared to Λc+ as a function of
xF, and on pt2 distributions for
Λc+. These data were measured in the same
apparatus using incident π-, Σ- beams at
600 GeV//c and proton beam at 540 GeV//c. The asymmetry is studied as a
function of xF. In the forward hemisphere with
xF>=0.2 both baryon beams exhibit very strong preference
for producing charm baryons rather than charm antibaryons, while the
pion beam asymmetry is much smaller. In this energy regime the results
show that beam fragments play a major role in the kinematics of
Λc formation, as suggested by the leading quark
picture.
Physics Letters B 01/2002; 528:49-57. · 3.95 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A method for detecting the transition \omutau in long-baseline accelerator experiments, that consists in comparing the far-to-near ratios of the spectra of quasielastic CC events generated by high- and low-energy beams of muon neutrinos, is proposed. The test may be accessible to big water Cherenkov detectors and iron--scintillator calorimeters, and is limited by statistics rather than systematics. Comment: 10 pages, 4 figures
01/2002;
-
[show abstract]
[hide abstract]
ABSTRACT: A method for detecting the transition numu->nutau in long-baseline accelerator experiments, that consists in comparing the far-to-near ratios of the spectra of quasielastic CC events generated by high- and low-energy beams of muon neutrinos, is proposed. The test may be accessible to big calorimeters with muon spectrometry like MINOS, and is limited by statistics rather than systematics.
09/2001;
-
A Kushnirenko,
G Alkhazov,
A G Atamantchouk,
M Y Balatz,
N F Bondar,
P S Cooper,
L J Dauwe,
G V Davidenko,
U Dersch,
A G Dolgolenko, [......],
D V Vavilov,
V S Verebryusov,
V A Victorov,
V E Vishnyakov,
A A Vorobyov,
K Vorwalter,
J You,
Z Wenheng,
Z Shuchen,
R Zukanovich-Funchal
[show abstract]
[hide abstract]
ABSTRACT: We report new precision measurements of the lifetimes of the Lambda(+)(c) and D0 from SELEX, the charm hadroproduction experiment at Fermilab. Based upon 1630 Lambda(+)(c) and 10 210 D0 decays we observe lifetimes of tau[Lambda(+)(c)] = 198.1+/-7.0+/-5.6 fs and tau[D0] = 407.9+/-6.0+/-4.3 fs.
Physical Review Letters 07/2001; 86(23):5243-6. · 7.37 Impact Factor
-
S Y Jun,
N Akchurin,
V A Andreev,
A G Atamantchouk,
M Aykac,
M Y Balatz,
N F Bondar,
A Bravar,
P S Cooper,
L J Dauwe, [......],
V A Victorov,
V E Vishnyakov,
A A Vorobyov,
K Vorwalter,
Z Wenheng,
J You,
L Yunshan,
M Zhenlin,
L Zhigang,
R Zukanovich Funchal
[show abstract]
[hide abstract]
ABSTRACT: We report the first observation of the Cabibbo-suppressed charm baryon decay Ξ_{c}^{+}→pK^{-}π^{+}. We observe 150±22±5 events for the signal. The data were accumulated using the SELEX spectrometer during the 1996-1997 fixed target run at Fermilab, chiefly from a 600 GeV/c Σ^{-} beam. The branching fractions of the decay relative to the Cabibbo-favored Ξ_{c}^{+}→Σ^{+}K^{-}π^{+} and Ξ_{c}^{+}→Ξ^{-}π^{+}π^{+} are measured to be B(Ξ_{c}^{+}→pK^{-}π^{+})/B(Ξ_{c}^{+}→Σ^{+}K^{-}π^{+})=0.22±0.06±0.03 and B(Ξ_{c}^{+}→pK^{-}π^{+})/B(Ξ_{c}^{+}→Ξ^{-}π^{+}π^{+})=0.20±0.04±0.02, respectively.
Physical Review Letters 02/2000; 84(9):1857-61. · 7.37 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A conceptual scheme of a hybrid-emulsion spectrometer for investigating various channels of neutrino oscillations is proposed. The design emphasizes detection of $\tau$ leptons by detached vertices, reliable identification of electrons, and good spectrometry for all charged particles and photons. A distributed target is formed by layers of low-Z material, emulsion-plastic-emulsion sheets, and air gaps in which $\tau$ decays are detected. The tracks of charged secondaries, including electrons, are momentum-analyzed by curvature in magnetic field using hits in successive thin layers of emulsion. The $\tau$ leptons are efficiently detected in all major decay channels, including \xedec. Performance of a model spectrometer, that contains 3 tons of nuclear emulsion and 20 tons of passive material, is estimated for different experimental environments. When irradiated by the $\nu_\mu$ beam of a proton accelerator over a medium baseline of $<L/E_\nu > \sim 1$ km/GeV, the spectrometer will efficiently detect either the \omutau and \omue transitions in the mass-difference region of $\Delta m^2 \sim 1$ eV$^2$, as suggested by the results of LSND. When exposed to the neutrino beam of a muon storage ring over a long baseline of $<L/E_\nu > \sim$ 10-20 km/GeV, the model detector will efficiently probe the entire pattern of neutrino oscillations in the region $\Delta m^2 \sim 10^{-2}-10^{-3}$ eV$^2$, as suggested by the data on atmospheric neutrinos. Comment: 34 pages, 8 figures
02/2000;
-
R F Barbosa,
I F Albuquerque,
N F Bondar,
R Carrigan,
D Chen,
P S Cooper,
Dai Lisheng,
A S Denisov,
A V Dobrovolsky,
T Dubbs, [......],
N K Terentyev,
S Timm,
I I Tkatch,
L N Uvarov,
A A Vorobyov,
Yan Jie,
Zhao Wenheng,
Zheng Shuchen,
Zhong Yuanyuan,
E761 Collaboration
[show abstract]
[hide abstract]
ABSTRACT: We have measured the lifetime of the ¯ using the Fermilab Proton Center 375 GeV/c charged hyperon beam. We obtained (80.430.800.14) ps. We also measured the lifetime of the , obtaining (80.38 0.400.14) ps, in agreement with the Particle Data Group value. A direct comparison between the two lifetimes from the ratio of the decay curves gives a fractional lifetime difference of / ¯ (0.061.12)%, consistent with equal lifetimes for baryon and antibaryon as required by CPT invariance.
Physical Review D. 12/1999; 61:031101(R).
-
S.V. Golovkin,
A.P. Kozhevnikov,
V.P. Kubarovsky,
A.I. Kulyavtsev,
V.F. Kurshetsov,
L.G. Landsberg,
V.V. Molchanov,
V.A. Mukhin,
V.I. Solyanik,
D.V. Vavilov, [......],
G.K. Kliger,
V.Z. Kolganov, M.A. Kubantsev,
G.S. Lomkatsi,
A.F. Nilov,
A.I. Sitnikov,
V.T. Smolyankin,
V.S. Verebrusov,
V.E. Vishnyakov,
A.V. Kubarovsky
[show abstract]
[hide abstract]
ABSTRACT: Quasiexclusive neutral meson production in pN-interactions is studied in experiments with the SPHINX facility operating in a proton beam from the IHEP accelerator (Ep = 70 GeV). The cross sections and the parameters of the differential distributions for ?o, P, - and Ko production in the deep fragmentation region (xF > 0.79 1 0.86) are presented. The results show that such proton quasiexclusive reactions with baryon exchange may be promising in searches for exotic mesons.
Zeitschrift für Physik A Hadrons and Nuclei 10/1997; 359(3):327-335.
-
I F Albuquerque,
N F Bondar,
R Carrigan,
D Chen,
P S Cooper,
Dai Lisheng,
A S Denisov,
A V Dobrovolsky,
T Dubbs,
A M F Endler, [......],
Tang Fukun,
N K Terentyev,
S Timm,
I I Tkatch,
L N Uvarov,
A A Vorobyov,
Yan Jie,
Zhao Wenheng,
Zheng Shuchen,
Zhong Yuanyuan
Physical Review Letters 04/1997; 78(17):3252. · 7.37 Impact Factor
-
V. G. Zaetz,
M. Aderholz,
V. V. Ammosov,
A. E. Asratyan,
T. Coghen,
O. Erriquez,
V. A. Gapienko,
G. S. Gapienko,
J. Guy,
G. T. Jones, [......],
U. F. Katz,
V. A. Korotkov,
S. P. Krutchinin, M. A. Kubantsev,
P. Marage,
D. R. O. Morrison,
N. Schmitz,
K. E. Varvell,
W. Venus,
W. Wittek
[show abstract]
[hide abstract]
ABSTRACT: Most of the measured events on hydrogen, deuterium and neon targets from BEBC at CERN and the 15-foot Bubble Chamber at Fermilab are combined to measure spin-density matrix elements for 0 production in the current-fragmentation region in neutrino and antineutrino charged-current interactions. The spin-alignment parameter is found to be 0.080.11 for neutrino and 0.410.11 for antineutrino interactions. The parity-odd density matrix element Im(10+–10) is consistent with zero in both reactions. In the combined neutrino and antineutrino data an indication of parity violation is observed: Im 1–1=0.380.16 atx
B
>0.2,Q
2>8 GeV2 andz>0.6.
Zeitschrift für Physik C 11/1995; 66(4):583-590.
