共查询到20条相似文献,搜索用时 46 毫秒
1.
M. Bisset N. Kersting J. Li F. Moortgat S. Moretti Q. L. Xie 《The European Physical Journal C - Particles and Fields》2006,45(2):477-492
Processes of the form pp → anything → XiXj →
+
+ notE are studied via a technique that may be viewed as an adaptation of time-honoured Dalitz plot analyses. Xi and Xj are new heavy states (with i, j =1, . . .,n), which may be identical or distinct; and
and
are necessarily distinct standard model (SM) fermion pairs whose invariant masses can be measured. A Dalitz-like plot of
said invariant masses,
versus
, exhibits a topology connected to the masses and specific decay chains of Xi and Xj. Aside from relatively minor details, observed patterns consist of a collection of box and wedge shapes. This collection
is model-dependent: comparison of the observed pattern to the possibilities for a specific model yields information on which
new particle pair combinations are actually being produced, information beyond that extractable from conventional one-dimensional
invariant mass distributions. The technique is illustrated via application to the minimal supersymmetric standard model (MSSM)
process pp →
→ e+e- + μ+μ- notE. Here the heavy states are neutralinos
(i = 2,3,4) - note that
is excluded - which are produced in gluino/squark (
/
) cascade decay chains. Even with fairly modest expectations for the LHC performance during the first few years, this method
still provides substantial insight into the neutralino mass spectrum and couplings if gluino/squark masses are relatively
low (≃ 400 GeV).
Arrival of the final proofs: 29 November 2005 相似文献
2.
M. Bisset F. Moortgat S. Moretti 《The European Physical Journal C - Particles and Fields》2003,30(3):419-434
We perform for the Large Hadron Collider (LHC) a detailed study of charged Higgs boson production via the top-bottom quark associated mode followed by decays into a chargino and a neutralino, with masses and couplings as given by the general minimal supersymmetric standard model (MSSM). We focus our attention on the region of parameter space with
and intermediate values of
, where identification of
via decays into standard model (SM) particles has proven to be ineffective. Modelling the CMS detector, we find that a signature consisting of three hard leptons accompanied by a hadronically reconstructed top quark plus substantial missing transverse energy, which may result from
decays, can be made viable over a large variety of initially overwhelming SM and MSSM backgrounds, provided MSSM input parameters are favourable: notably, small
and light sleptons are important prerequisites. We quantify these statements by performing a fairly extensive scan of the parameter space, including realistic hadron-level simulations, and delineate some potential discovery regions.Received: 16 April 2003, Revised: 23 June 2003, Published online: 29 August 2003S. Moretti: Formerly at: Theory Division, CERN, 1211 Geneva 23, Switzerland and Institute for Particle Physics Phenomenology, University of Durham, Durham DH1 3LE, UK 相似文献
3.
A. Bharucha S. Heinemeyer F. von der Pahlen 《The European Physical Journal C - Particles and Fields》2013,73(11):1-22
We re-assess the exclusion limits on the parameters describing the supersymmetric (SUSY) electroweak sector of the MSSM obtained from the search for direct chargino–neutralino production at the LHC. We start from the published limits obtained for simplified models, where for the case of heavy sleptons the relevant branching ratio, $\mathrm {BR}(\tilde{\chi}^{0}_{2} \to \tilde{\chi}^{0}_{1} Z)$ , is set to one. We show how the decay mode $\tilde{\chi}^{0}_{2} \to \tilde{\chi}^{0}_{1} h$ , which cannot be neglected in any realistic model once kinematically allowed, substantially reduces the excluded parameter region. We analyze the dependence of the excluded regions on the phase of the gaugino soft SUSY-breaking mass parameter, M 1, on the mass of the light scalar tau, $m_{{\tilde{\tau}_{1}}}$ , on tanβ as well as on the squark and slepton mass scales. Large reductions in the ranges of parameters excluded can be observed in all scenarios. The branching ratios of charginos and neutralinos are evaluated using a full NLO calculation for the complex MSSM. The size of the effects of the NLO calculation on the exclusion bounds is investigated. We furthermore assess the potential reach of the experimental analyses after collecting 100 fb?1 at the LHC running at 13 TeV. 相似文献
4.
A. Bartl K. Hohenwarter-Sodek T. Kernreiter H. Rud 《The European Physical Journal C - Particles and Fields》2004,36(4):515-522
We consider the process
at a linear collider with transverse
beam polarization. We investigate the influence of the CP phases on azimuthal asymmetries in
with subsequent two-body decays
and
. We show that triple product correlations involving the transverse
beam polarization vanish if at least one subsequent chargino decay is not observed. We derive this result within the minimal supersymmetric standard model (MSSM) with complex parameters; however, it holds also in the general MSSM with SUSY flavor violation.Received: 29 March 2004, Published online: 30 July 2004 相似文献
5.
F. P. Heßberger S. Hofmann D. Ackermann S. Antalic B. Kindler I. Kojouharov P. Kuusiniemi M. Leino B. Lommel R. Mann K. Nishio A. G. Popeko B. Sulignano S. Saro B. Streicher M. Venhart A. V. Yeremin 《The European Physical Journal A - Hadrons and Nuclei》2006,30(3):561-569
The decay of the isotopes 255Rf, 251No and 247Fm produced in the reactions
, and
was investigated by means of α-γ spectroscopy. Previously observed γ transitions in coincidence with α decays of 255Rf were confirmed, their energies and line intensities were measured more precisely, and their multipolarities were determined
as E1. In 251No a new isomeric state at E
* > 1700keV with a half-life of ≈ 2μs was identified. The decay of 247Fm was measured more precisely. A partial level scheme of the daughter nucleus 243Cf could be established. 相似文献
6.
In the minimal supersymmetric standard model (MSSM), we study the light Higgs boson radiation off a light-chargino pair in the process
at linear colliders with
GeV. We analyze cross sections in the regions of the MSSM parameter space where the process
cannot proceed via on-shell production and subsequent decay of either heavier charginos or the pseudoscalar Higgs boson A. Cross sections up to a few fb are allowed, according to present experimental limits on the Higgs boson, chargino and sneutrino masses. We also show how a measurement of the
production rate could provide a determination of the Higgs boson couplings to charginos.Received: 24 June 2004, Revised: 13 May 2005, Published online: 19 July 2005 相似文献
7.
《The European Physical Journal C - Particles and Fields》2008,54(3):345-364
A determination of the single W spin density matrix (SDM) elements in the reaction e+e-→W+W-→lνqq̄(l=e/μ) is reported at centre-of-mass energies between 189 and 209 GeV. The data sample used corresponds to an integrated
luminosity of 520 pb-1 taken by DELPHI between 1998 and 2000.
The single W SDM elements, ρττ’
W± (τ,τ’=± 1 or 0), are determined as a function of the W- production angle with respect to the e- beam direction and are obtained from measurements of the W decay products by the application of suitable projection operators,
Λττ’, which assume the V-A coupling of the W-boson to fermions.
The measured SDM elements are used to obtain the fraction of longitudinally polarised Ws, with the result: at a mean energy of 198 GeV. The SDM elements are also used to determine the triple gauge couplings Δg1
Z,Δκγ,λγ and g4
Z, and . For the CP-violating couplings the results of single parameter fits are:
The errors are a combination of statistical and systematic errors. All results are consistent with the Standard Model. 相似文献
8.
Zhi-Qing Zhang Zhen-Jun Xiao 《The European Physical Journal C - Particles and Fields》2009,59(1):49-66
We calculate the important next-to-leading-order (NLO) contributions to the B→KK
* decays from the vertex corrections, the quark loops, and the magnetic penguins in the perturbative QCD (pQCD) factorization
approach. The pQCD predictions for the CP-averaged branching ratios are
,
,
and Br(B
0→K
+
K
*−+K
−
K
*+)≈1.3×10−7, which agree well with both the experimental upper limits and the predictions based on the QCD factorization approach. Furthermore,
the CP violating asymmetries of the considered decay modes are also evaluated. The NLO pQCD predictions for
and
decays are
and
. 相似文献
9.
O. Kittel G. Moortgat-Pick K. Rolbiecki P. Schade M. Terwort 《The European Physical Journal C - Particles and Fields》2012,72(1):1854
We study the prospects to measure the CP-sensitive triple-product asymmetries in neutralino production \(e^{+} e^{-} \to\tilde{\chi}^{0}_{i}\tilde{\chi}^{0}_{1}\) and subsequent leptonic two-body decays \(\tilde{\chi}^{0}_{i} \to \tilde{\ell}_{R} \ell\), \(\tilde{\ell}_{R} \to \tilde{\chi}^{0}_{1} \ell\), for ?=e,μ, within the Minimal Supersymmetric Standard Model. We include a full detector simulation of the International Large Detector for the International Linear Collider. The simulation was performed at a center-of-mass energy of \(\sqrt{s}=500\) GeV, including the relevant Standard Model background processes, a realistic beam energy spectrum, beam backgrounds and a beam polarization of 80% and ?60% for the electron and positron beams, respectively. In order to effectively disentangle different signal samples and reduce SM and SUSY backgrounds we apply a method of kinematic reconstruction. Assuming an integrated luminosity of 500 fb?1 collected by the experiment and the performance of the current ILD detector, we arrive at a relative measurement accuracy of 10% for the CP-sensitive asymmetry in our scenario. We demonstrate that our method of signal selection using kinematic reconstruction can be applied to a broad class of scenarios and it allows disentangling processes with similar kinematic properties. 相似文献
10.
For weakly non ergodic systems, the probability density function of a time average observable
is
where
is the value of the observable when the system is in state j=1,…L. p
j
eq is the probability that a member of an ensemble of systems occupies state j in equilibrium. For a particle undergoing a fractional diffusion process in a binding force field, with thermal detailed
balance conditions, p
j
eq is Boltzmann’s canonical probability. Within the unbiased sub-diffusive continuous time random walk model, the exponent 0<α<1 is the anomalous diffusion exponent 〈x
2〉∼t
α
found for free boundary conditions. When α→1 ergodic statistical mechanics is recovered
. We briefly discuss possible physical applications in single particle experiments. 相似文献
11.
We present a complete one-loop study of the process
and the predicted cross section in a
Linear Collider. A suitable numerical code, PLATONlc, valid for any set of real MSSM parameters, is released. This study and code are complementary to those suitable for dark matter detection through the inverse process
describing neutralino-neutralino annihilation at rest, which were presented previously. If SUSY is realized in nature, both codes should be very helpful in future astrophysical and collider studies of the neutralino sector.Received: 6 November 2003, Published online: 9 January 2004Programme dActions Intégrées Franco-Hellenique, Platon 04100 UM. 相似文献
12.
For the search for charginos and neutralinos in the Minimal Supersymmetric Standard Model (MSSM) as well as for future precision analyses of these particles an accurate knowledge of their production and decay properties is mandatory. We evaluate the cross sections for the chargino and neutralino production at \(e^+e^-\) colliders in the MSSM with complex parameters (cMSSM). The evaluation is based on a full one-loop calculation of the production mechanisms \(e^+e^- \rightarrow {\tilde{\chi }}_{c}^\pm {\tilde{\chi }}_{c^\prime }^\mp \) and \(e^+e^- \rightarrow {\tilde{\chi }}_{n}^0 {\tilde{\chi }}_{n^\prime }^0\) including soft and hard photon radiation. We mostly restricted ourselves to a version of our renormalization scheme which is valid for \(|M_1| < |M_2|, |\mu |\) and \(M_2 \ne \mu \) to simplify the analysis, even though we are able to switch to other parameter regions and correspondingly different renormalization schemes. The dependence of the chargino/neutralino cross sections on the relevant cMSSM parameters is analyzed numerically. We find sizable contributions to many production cross sections. They amount to roughly \({\pm }15\%\) of the tree-level results but can go up to \({\pm }40\%\) or higher in extreme cases. Also the complex phase dependence of the one-loop corrections was found non-negligible. The full one-loop contributions are thus crucial for physics analyses at a future linear \(e^+e^-\) collider such as the ILC or CLIC. 相似文献
13.
S. R. Gevorkyan D. T. Madigozhin A. V. Tarasov O. O. Voskresenskaya 《Physics of Particles and Nuclei Letters》2008,5(2):85-87
The final state interactions in K
± → π±π0π0 decays are considered using the methods of nonrelativistic quantum mechanics. It is shown how to take into account the largest
electromagnetic effect in the analysis of experimental data using the amplitudes calculated earlier. The relevant expressions
for amplitude corrections valid both above and below the two charged pions production threshold , including the average effect for the threshold bin, are proposed. These formulae can be used in the procedure of pion scattering
lengths measurement from spectrum.
The text was submitted by the authors in English. 相似文献
14.
J. Ellis F. Moortgat G. Moortgat-Pick J. M. Smillie J. Tattersall 《The European Physical Journal C - Particles and Fields》2009,60(4):633-651
We study the potential observation at the LHC of CP-violating effects in stop production and subsequent cascade decays,
,
,
, within the Minimal Supersymmetric Standard Model. We study T-odd asymmetries based on triple products between the different
decay products. There may be a large CP asymmetry at the parton level, but there is a significant dilution at the hadronic
level after integrating over the parton distribution functions. Consequently, even for scenarios where large CP intrinsic
asymmetries are expected, the measurable asymmetry is rather small. High luminosity and precise measurements of masses, branching
ratios and CP asymmetries may enable measurements of the CP-violating parameters in cascade decays at the LHC. 相似文献
15.
S. Heinemeyer V.A. Khoze M.G. Ryskin W.J. Stirling M. Tasevsky G. Weiglein 《The European Physical Journal C - Particles and Fields》2008,53(2):231-256
We show that the use of forward proton detectors at the LHC installed at 220 m and 420 m distance around ATLAS and/or CMS
can provide important information on the Higgs sector of the MSSM. We analyse central exclusive production of the neutral
-even Higgs bosons h and H and their decays into bottom quarks, τ leptons and W bosons in various MSSM benchmark scenarios.
Using plausible estimates for the achievable experimental efficiencies and the relevant background processes, we find that
the prospective sensitivity of the diffractive Higgs production will allow one to probe interesting regions of the MA–tanβ parameter plane of the MSSM. Central exclusive production of the -even Higgs bosons of the MSSM may provide a unique opportunity to access the bottom Yukawa couplings of the Higgs bosons
up to masses of MH≲ 250 GeV. We also discuss the prospects for identifying the -odd Higgs boson, A, in diffractive processes at the LHC. 相似文献
16.
A Monte-Carlo analysis on production and decay of supersymmetric charginos at a future photon-collider is presented. A photon collider offers the possibility of a direct branching-ratio measurement. In this study, the process
has been considered for a specific mSUGRA scenario. Various backgrounds and a parameterised detector simulation have been included. Depending on the centre-of-mass energy, a statistical error for the directly measurable branching ratio BR(
) of up to 3.5% can be reached.Received: 14 March 2005, Revised: 31 May 2005, Published online: 28 June 2005G. Klämke: Now at: Institut für Theoretische Physik, Universität Karlsruhe, Wolfgang-Gaede-Str. 1, 76131 Karlsruhe, Germany 相似文献
17.
The decay chain
is identified in a sample of 3.9 million hadronic Z decays collected with the OPAL detector at LEP. The branching ratio BR
is measured to be
for the J
P
=1+ (D0
1) state. For decays into the J
P
=2+ (D2
*0) state, an upper limit of 1.4 x 10-3 is placed on the branching ratio at the 95% confidence level.Received: 20 December 2002, Revised: 15 April 2003, Published online: 12 September 2003 相似文献
18.
Zhi-Gang Wang 《The European Physical Journal C - Particles and Fields》2009,61(2):321-329
We calculate the masses and the pole residues of the
heavy baryons Ω
c
0(css) and Ω
b
−(bss) with the QCD sum rules. The numerical values
GeV (or
GeV) and
GeV (or
GeV) are in good agreement with the experimental data. 相似文献
19.
《The European Physical Journal C - Particles and Fields》2007,50(2):269-281
A search for stop production in R-parity-violating supersymmetry has been performed in e+p interactions with the ZEUS detector at HERA, using an integrated luminosity of 65 pb-1. At HERA, the R-parity-violating coupling λ’ allows resonant squark production, . Since the lowest-mass squark state in most supersymmetry models is the light stop, , this search concentrated on production of , followed either by a direct R-parity-violating decay, or by the gauge decay to . No evidence for stop production was found and limits were set on λ’131 as a function of the stop mass in the framework of the minimal supersymmetric standard model. The results have also been
interpreted in terms of constraints on the parameters of the minimal supergravity model. 相似文献
20.