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Heavy baryons - Recent and very new results

Description: Recent results on observations, properties and decay modes of the charmed and beauty baryons will be reviewed. Candidates for several new high mass states which include a cleanly-identified daughter {Lambda}{sub c}{sup +} baryon are seen in data from the SELEX experiment at Fermilab. These states are candidates for doubly-charmed baryons: a {Xi}{sub cc}{sup ++} state and a {Xi}{sub cc}{sup +} state. These candidates are more than 5{sigma} signals in each case at masses of 3520 and 3460 MeV respectively.
Date: January 15, 2003
Creator: Cooper, Peter S
Partner: UNT Libraries Government Documents Department

First charm baryon physics from SELEX(E781)

Description: We present preliminary results on various aspects of charm baryon studies at the 1996-1997 fixed target experiment of Fermilab studying charm produced from incident {Sigma}{sup -}, proton, and {pi}{sub -} beams at 600 GeV. First results include the comparison of hadroproduction asymmetries for {Lambda}{sub c}{sup +} production from the 3 beams as well xF distributions and the first observation of the Cabbibo-suppressed decay {Xi}{sub c}{sup +} {yields} pK{sup -}{pi}{sup +}. The relative branching fraction of the Cabbibo-suppressed mode to the 3-body Cabbibo-favored modes is also presented.
Date: April 16, 1999
Creator: Jun, F. G. Garcia and S. Y.
Partner: UNT Libraries Government Documents Department

Strange decays of nonstrange baryons

Description: The strong decays of excited nonstrange baryons into the final states {Lambda}K, {Sigma}K, and for the first time into {Lambda}(1405)K, {Lambda}(1520)K, {Sigma}(1385)K, {Lambda}K{sup *}, and {Sigma}K{sup *}, are examined in a relativized quark pair creation model. The wave functions and parameters of the model are fixed by previous calculations of N{pi} and N{pi}{pi}, etc., decays. The results show that it should be possible to discover several new negative parity excited baryons and confirm the discovery of several others by analyzing these final states in kaon production experiments. They also establish clear predictions for the relative strengths of certain states to decay to {Lambda}(1405)K and {Lambda}(1520)K, which can be tested to determine if a three-quark model of the {Lambda}(1405)K is valid. The authors results compare favorably with the results of partial wave analyses of the limited existing data for the {Lambda}K and {Sigma}K channels. They do not find large {Sigma}K decay amplitudes for a substantial group of predicted and weakly established negative-parity states, in contrast to the only previous work to consider decays of these states into the strange final states {Lambda}K and {Sigma}K.
Date: April 1, 1998
Creator: Capstick, Simon & Roberts, W.
Partner: UNT Libraries Government Documents Department

Properties of Heavy B Hadrons

Description: We review recent measurements of heavy B hadron states including masses and lifetimes of the B{sub c}{sup -} meson as well as excited B states (B**, B**{sub s}). We discuss properties of the B{sub s}{sup 0} meson such as lifetime, lifetime difference {Delta}{Lambda}{sub s}/{Lambda}{sub s} and CP violation in B{sub s}{sup 0} {yields} J/{psi}{phi} decays. We also summarize new measurements of the masses and lifetimes of bottom baryons including the {Lambda}{sub b}{sup 0} baryon, the {Sigma}{sub b} baryon states as well as the {Xi}{sub b}{sup -} and {Omega}{sub b}{sup -} baryons.
Date: April 1, 2009
Creator: Paulini, Manfred
Partner: UNT Libraries Government Documents Department

SELEX: Recent Progress in the Analysis of Charm-Strange and Double-Charm Baryons

Description: SELEX (Fermilab Experiment 781) [1] employs beams of {Sigma}{sup -}, {pi}{sup -}, and protons at around 600 GeV/c to study production and decay properties of charmed baryons. It took data in the 1996/7 fixed target run and is currently analyzing those data. Here they focus on recently obtained results concerning the {Omega}{sub c}{sup 0} lifetime and the doubly-charmed baryons {Xi}{sub cc}{sup +} and {Xi}{sub cc}{sup ++}.
Date: February 1, 2007
Creator: Engelfried, Jurgen
Partner: UNT Libraries Government Documents Department

Photoproduction amplitudes of P(sub)11 and P(sub)33 baryon resonances in the quark model

Description: Predictions are made for the photoproduction amplitudes of low-lying N^(1/2)+ (P(sub)(11)) and delta^(3/2)+ (P(sub)(33)) resonances, using a quark model with relativistic corrections to the transition operator, and mixed nonrelativistic wavefunctions which are correctly orthogonal to the ground states.These amplitudes are also calculated using relativized model wavefunctions. The results for the Roper resonance N(1440) are in marked disagreement with the data.
Date: January 1, 1992
Creator: Capstick, Simon
Partner: UNT Libraries Government Documents Department

Even parity theta-pentaquark and stable strange nuclear matter

Description: The newly discovered exotic {Theta} baryon of mass 1540 MeV (and very small width) truly has a very low mass, if it is a pentaquark system of even parity. A schematic model in which the coherent interaction of u{bar s} and d{bar s} pairs leads to a very large residual (non-confining) attractive interaction is introduced. This collective vibrational model accounts for the mass and small decay width to the KN channel, but yields a significant coupling to the virtual K*N channel. The schematic model predicts an attractive {Theta}-nucleon interaction strong enough to bind a {Theta} particle to a nucleus in a state that is stable against decay via strong interactions. The discovery of {Theta}-nuclei could be a definitive proof that the {Theta} parity is even.
Date: March 2, 2004
Creator: Miller, Gerald A.
Partner: UNT Libraries Government Documents Department

Naturalness of the Coleman-Glashow mass relation in the 1/N{sub c} expansion: An update

Description: A new measurement of the {Xi}{sup 0} mass verifies the accuracy of the Coleman-Glashow relation at the level predicted by the 1/N{sub c} expansion. Values for other baryon isospin mass splittings are updated, and continue to agree with the 1/N{sub c} hierarchy.
Date: May 1, 2000
Creator: Jenkins, E. & Lebed, R.F.
Partner: UNT Libraries Government Documents Department

Quark-Hadron Duality

Description: Quark-hadron duality and its potential applications are discussed. We focus on theoretical efforts to model duality.
Date: March 1, 2002
Creator: Jeschonnek, Sabine & Orden, J.W. Van
Partner: UNT Libraries Government Documents Department

Broken SU(3) antidecuplet for {Theta}{sup +} and {Xi}{sub 3/2}

Description: If the narrow exotic baryon resonances {Theta}{sup +}(1540) and {Xi}{sub 3/2} are members of the J{sup P} = 1/2{sup +} antidecuplet with N*(1710), the octet-antidecuplet mixing is required not only by the mass spectrum but also by the decay pattern of N*(1710). This casts doubt on validity of the {Theta}{sup +} mass prediction by the chiral soliton model. While all pieces of the existing experimental information point to a small octet-decuplet mixing, the magnitude of mixing required by the mass spectrum is not consistent with the value needed to account for the hadronic decay rates. The discrepancy is not resolved even after the large experimental uncertainty is taken into consideration. We fail to find an alternative SU(3) assignment even with different spin-parity assignment. When we extend the analysis to mixing with a higher SU(3) multiplet, we find one experimentally testable scenario in the case of mixing with a 27-plet.
Date: May 5, 2004
Creator: Pakvasa, Sandip & Suzuki, Mahiko
Partner: UNT Libraries Government Documents Department

First observation of doubly charmed baryons

Description: The SELEX experiment (E781) at Fermilab has observed two statistically compelling high mass states near 3.6 GeV/c{sup 2}, decaying to {Lambda}{sub c}{sup +} K{sup -} {pi}{sup +} and {Lambda}{sub c}{sup +} K{sup -} {pi}{sup +}{pi}{sup +}. These final states are Cabibbo-allowed decay modes of doubly charmed baryons {Xi}{sub cc}{sup +} and {Xi}{sub cc}{sup ++}, respectively. The masses are in the range expected from theoretical considerations, but the spectroscopy is surprising. SELEX also has weaker preliminary evidence for a state near 3.8 GeV/c{sup 2}, a high mass state decaying to {Lambda}{sub c}{sup +} K{sup -} {pi}{sup +}{pi}{sup +}, possibly an excited {Xi}{sub cc}{sup ++} (ccu*). Data are presented and discussed.
Date: September 25, 2003
Creator: al., M. A. Moinester et
Partner: UNT Libraries Government Documents Department

Binding energies of hypernuclei and hypernuclear interactions

Description: In part 1 the effect of nuclear core dynamics on the binding energies of {Lambda} hypernuclei is discussed in the framework of variational correlated wave functions. In particular, the authors discuss a new rearrangement energy contribution and its effect on the core polarization. In part 2 they consider the interpretation of the {Lambda} single-particle energy in terms of basic {Lambda}-nuclear interactions using a local density approximation based on a Fermi hypernetted chain calculation of the A binding to nuclear matter. To account for the data strongly repulsive 3-body {Lambda}NN forces are required. Also in this framework they discuss core polarization for medium and heavier hypernuclei.
Date: May 1, 1996
Creator: Bodmer, A.R.; Murali, S. & Usmani, Q.N.
Partner: UNT Libraries Government Documents Department

Baryon Triality And Neutrino Masses From An Anomalous FlavorU(1)

Description: We construct a concise U(1){sub X} Froggatt-Nielsen model in which baryon triality, a discrete gauge Z{sub 3}-symmetry, arises from U(1){sub X} breaking. The proton is thus stable, however, R-parity is violated. With the proper choice of U(1){sub X} charges we can obtain neutrino masses and mixings consistent with an explanation of the atmospheric and solar neutrino anomalies in terms of neutrino oscillations, with no right-handed neutrinos required. The only mass scale apart from M{sub grav} is m{sub soft}.
Date: August 15, 2007
Creator: Dreiner, Herbi K.; Luhn, Christoph; Murayama, Hitoshi & Thormeier,Marc
Partner: UNT Libraries Government Documents Department

Heavy quark symmetries and the decays baryon antibaryon

Description: We enumerate the form factors necessary to describe the two-body baryonic decays of B mesons.We use the symmetries of the heavy quark effective theory to arrive at some relations among these form factors, when at least one of the daughter baryons is heavy.
Date: October 1, 1991
Creator: Roberts, Winston; Roberts, Winston & Ryzak, Z.
Partner: UNT Libraries Government Documents Department

Quasi two-body decays of nonstrange baryons.

Description: We examine the decays of nonstrange baryons to the final states Delta Pi, NRho, NEta, NEta', Nw, N.5 (1440)Pi, and Delta 3/2+(1600)Pi, in a relativized pair-creation (^3Po) model which has been developed in a previous study of the NPi decays of the same baryon states.As it is our goal to provide a guide for the possible discovery of new baryon states at CEBAF and elsewhere, we examine the decays of resonances which have already been seen in the partial-wave analyses, along with those of states which are predicted by the quark model but which remain undiscovered.The level of agreement between our calculation and the available widths from the partial-wave analyses in encouraging.
Date: August 1, 1993
Creator: Roberts, Winston & Capstick, Simon
Partner: UNT Libraries Government Documents Department

New baryons in the {Delta}{eta} and {Delta}{omega} channels

Description: The decays of excited nonstrange baryons into the final states {Delta}{eta} and {Delta}{omega} are examined in a relativized quark pair creation model. The wavefunctions and parameters of the model are fixed by previous calculations of N{pi} and N{pi}{pi}, etc., decays through various quasi-two body channels including N{eta} and N{omega}. The results show that the combination of thresholds just below the region of interest and the isospin selectivity of these channels should allow the discovery of several new baryons in such experiments.
Date: July 1, 1998
Creator: Capstick, Simon & Roberts, W.
Partner: UNT Libraries Government Documents Department

An Alternative View of the Dynamical Origin of the P11 Nucleon Resonances: Results from the Excited Baryon Analysis Center

Description: We present an alternative interpretation for the dynamical origin of the P{sub 11} nucleon resonances, which results from the dynamical coupled-channels analysis at Excited Baryon Analysis Center of Jefferson Lab. The results indicate the crucial role of the multichannel reaction dynamics in determining the N* spectrum. An understanding of the spectrum and structure of the excited nucleon (N*) states is a fundamental challenge in the hadron physics. The N* states, however, couple strongly to the meson-baryon continuum states and appear only as resonance states in the {gamma}N and {pi}N reactions. One can expect from such strong couplings that the (multichannel) reaction dynamics will affect significantly the N* states and cannot be neglected in extracting the N* parameters from the data and giving physical interpretations. It is thus well recognized nowadays that a comprehensive study of all relevant meson production reactions with {pi}N,{eta}N,{pi}{pi}N,KY, {hor_ellipsis} final states is necessary for a reliable extraction of the N* parameters. To address this challenging issue, the Excited Baryon Analysis Center (EBAC) of Jefferson Lab has been conducting the comprehensive analysis of the world data of {gamma}N,{pi}N {yields} {pi}N,{eta}N,{pi}{pi}N,KY, {hor_ellipsis} reactions systematically, covering the wide energy and kinematic regions. The analysis is pursued with a dynamical coupled-channels (DCC) model, the EBAC-DCC model, within which the unitarity among relevant meson-baryon channels, including the three-body {pi}{pi}N channel, is fully taken into account.
Date: April 1, 2012
Creator: Kamano, Hiroyuki
Partner: UNT Libraries Government Documents Department

Measurements of Direct CP Violating Asymmetries in Charmless Decays of Strange Bottom Mesons and Bottom Baryons

Description: We report measurements of direct CP-violating asymmetries in charmless decays of neutral bottom hadrons to pairs of charged hadrons with the upgraded Collider Detector at the Fermilab Tevatron. Using a data sample corresponding to 1 fb{sup -1} of integrated luminosity, we obtain the first measurements of direct CP violation in bottom strange mesons, A{sub CP}(B{sub s}{sup 0} {yields} K{sup -}{pi}{sup +}) = +0.39 {+-} 0.15 (stat) {+-} 0.08 (syst), and botton baryons, A{sub CP}({Lambda}{sub b}{sup 0} {yields} p{pi}{sup -}) = + 0.03 {+-} 0.17 (stat) {+-} 0.05 (syst) and A{sub CP} ({Lambda}{sub b}{sup 0} {yields} pK{sup -}) = +0.37 {+-} 0.17 (stat) {+-} 0.03 (syst). In addition, they measure CP violation in B{sup 0} {yields} K{sup +}{pi}{sup -} decays with 3.5{sigma} significance, A{sub CP} (B{sup 0} {yields} K{sup +}{pi}{sup -}) = -0.086 {+-} 0.023 (stat) {+-} 0.009 (syst), in agreement with the current world average. Measurements of branching fractions of B{sub s}{sup 0} {yields} K{sup +}K{sup -} and B{sup 0} {yields} {pi}{sup +}{pi}{sup -} decays are also updated.
Date: March 1, 2011
Creator: Aaltonen, T.; Aaltonen, T.; Phys., /Helsinki Inst. of; Alvarez Gonzalez, B.; Phys., /Oviedo U. /Cantabria Inst. of; Amerio, S. et al.
Partner: UNT Libraries Government Documents Department

Pion-nucleon scattering in P{sub 11} channel and the Roper resonance

Description: The {pi}N scattering in P{sub 11} channel is investigated within the two-channel model of Pearce and Afnan. The model consists of: (1) vertex interactions b {yields} {pi}N, {pi}{nabla} with b denoting either a bare nucleon or a bare Roper state, (2) a background potential {upsilon}{sub {pi}B,{pi}B} with B = N,{nabla}. Assuming that {upsilon}{sub {pi}B,{pi}B} can be phenomenologically parameterized as a separable form and the {pi}N inelasticity can be accounted for by dressing the {nabla} in the {pi}{nabla} channel by a {nabla} {leftrightarrow} {pi}N vertex, it is found that the fit to the P{sub 11} phase shifts up to 1 GeV favors a large mass of the bare Roper state. Our results are consistent with the findings of Pearce and Afnan that if the mass of the bare Roper state is restricted to be {le}1600 MeV, then a physical Roper will have a width which is too narrow causing a rapid variation of the phase shifts at energies near the resonance energy.
Date: March 1996
Creator: Bugaev, K. A.; Yang, Shin Nan & Lee, T. S. H.
Partner: UNT Libraries Government Documents Department

Properties of Weakly-decaying Bottom Baryons, Xi_b^- and Omega_b^-, at CDF

Description: We present properties of weakly decaying bottom baryons, {Xi}{sub b}{sup -} and {Omega}{sub b}{sup -}, using 4.2 fb{sup -1} of data from p{bar p} collisions at {radical}s = 1.96 TeVf, and recorded with the Collider Detector at Fermilab. They report the observation of the {Omega}{sub b}{sup -} through the decay chain {Omega}{sub b}{sup -} {yields} J/{psi}{omega}{sup -}, where J/{psi} {yields} {mu}{sup +}{mu}{sup -}, {Omega}{sup -} {yields} {Lambda}K{sup -}, and {Lambda} {yields} p{pi}{sup -}. Significance of the observed signal is estimated to be 5.5 Gaussian standard deviations. The {Omega}{sub b}{sup -} mass and lifetime are measured to be 6054.4 {+-} 6.8(stat.) {+-} 0.9(syst.) MeV/c{sup 2} and 1.13{sub -0.40}{sup +0.53}(stat.) {+-} 0.02(syst). ps, respectively. In addition, the mass and lifetime of the {Xi}{sub b}{sup -} baryon are measured to be 5790.9 {+-} 2.6(stat.) {+-} 0.8(syst.) MeV/c{sup 2} and 1.56{sub -0.25}{sup +0.27}(stat.) {+-} 0.02(syst.) ps, respectively. Under the assumption that the {Xi}{sub b}{sup -} and {Omega}{sub b}{sup -} are produced with similar kinematic distributions as the {Lambda}{sub b}{sup 0} baryon, we measure {sigma}({Xi}{sub b}{sup -}){Beta}({Xi}{sub b}{sup -}) {yields} J/{psi}({Xi}{sup -})/{sigma}({Lambda}{sub b}{sup 0}){Beta}({Lambda}{sub b}{sup 0} {yields} J/{psi} {Lambda}) = 0.167{sub -0.025}{sup +0.037}(stat.) {+-} 0.012(syst.) and {sigma}({omega}{sub b}{sup -}){Beta}({Omega}{sub b}{sup -} J/{psi} {Omega}{sup -})/{sigma}({Lambda}{sub b}{sup 0}){Beta}({Lambda}{sub b}{sup 0}) {yields} J/{psi} {Lambda} = 0.045{sub 0.012}{sup +0.017}(stat.) {+-} 0.004(syst.) for baryons produced with transverse momentum in the range of 6-20 GeV/c.
Date: October 1, 2009
Creator: Behari, Satyajit & Collaboration, for the CDF
Partner: UNT Libraries Government Documents Department

Observation of the sigma_b baryons at CDF

Description: We present a measurement of four new bottom baryons in proton-antiproton collisions with a center of mass energy of 1.96 TeV. Using 1.1 fb{sup -1} of data collected by the CDF II detector, we observe four {Lambda}{sup 0}{sub b}{pi}{+-} resonances in the fully reconstructed decay mode {Lambda}{sup 0}{sub b} {yields} {Lambda}{sup +}{sub c}{pi}{sup -}, where {Lambda}{sup +}{sub c} {yields} pK{sup -}{pi}{sup +}. The probability for the background to produce a similar or larger signal is less than 8.3 x 10{sup -8}, corresponding to a significance of greater than 5.2 {sigma}. We interpret these baryons as the {Sigma}{sub b}{sup (*){+-}} baryons.
Date: March 1, 2007
Creator: Pursley, Jennifer M. & U., /Johns Hopkins
Partner: UNT Libraries Government Documents Department