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1.
S. Y. Choi 《The European Physical Journal C - Particles and Fields》2009,59(2):543-556
The next-generation high-energy facilities, the CERN Large Hadron Collider (LHC) and the prospective e
+
e
− International Linear Collider (ILC), are expected to unravel new structures of matter and forces from the electroweak scale
to the TeV scale. In this report we review the complementary role of LHC and ILC in drawing a comprehensive and high-precision
picture of the mechanism breaking the electroweak symmetries and generating mass, and the unification of forces in the frame
of supersymmetry.
Extended version of Ref. [1] to be published in “Supersymmetry on the Eve of the LHC”, a special volume of European Physical Journal C, Particles and
Fields (EPJC) in memory of Julius Wess. 相似文献
2.
Simulation study of χc→J/Ψ+γ detection with J/Ψ→e+e? in pp collisions in the ALICE experiment at LHC
P. González P. Ladrón de Guevara E. López Torres A. Marín E. Serradilla 《The European Physical Journal C - Particles and Fields》2009,61(4):915-903
We present Monte Carlo preliminary results about the feasibility to detect the χ
c
family in p-p collisions at 14 TeV in the ALICE Central Barrel at CERN LHC. The χ
c1 and χ
c2 were forced to decay in the radiative channel J/Ψ+γ→e
+
e
−+γ and were merged with a proton-proton non-biased collision. After Monte Carlo transport and simulation of the detector response,
the e
+, e
− and converted γ were reconstructed and identified in the ALICE ITS, TPC and TRD detectors. Separate signals corresponding to γ from χ
c1 and from χ
c2 were observed. The position and relative weight of the fit to gaussians agreed with the input values within the statistical
limits.
An erratum to this article can be found at 相似文献
3.
Fei Wang Wenyu Wang Fuqiang Xu Jin Min Yang Huanjun Zhang 《The European Physical Journal C - Particles and Fields》2007,51(3):713-719
In split supersymmetry, gauginos and higgsinos are the only supersymmetric particles possibly accessible at foreseeable colliders
like the CERN Large Hadron Collider (LHC) and the International Linear Collider (ILC). In order to account for the cosmic
dark matter measured by WMAP, these gauginos and higgsinos are stringently constrained and could be explored at the colliders
through their direct productions and/or virtual effects in some processes. The clean environment and high luminosity of the
ILC render the virtual effects at percent level meaningful in unraveling the new physics effects. In this work we assume split
supersymmetry and calculate the virtual effects of the WMAP-allowed gauginos and higgsinos in the Higgs productions e+e-→Zh and e+e-→νeν̄eh through WW fusion at the ILC. We find that the production cross section of e+e-→Zh can be altered by a few percent in some part of the WMAP-allowed parameter space, while the correction to the WW fusion
process e+e-→νeν̄eh is below 1%. Such virtual effects are correlated with the cross sections of chargino pair productions and can offer complementary
information in probing split supersymmetry at the colliders.
PACS 14.80.Ly; 95.35.+d 相似文献
4.
MOHAMMAD EBRAHIM ZOMORRODIAN ALIREZA SEPEHRI TOORAJ GHAFFARY PARVIN ESLAMI 《Pramana》2011,76(1):93-107
The hadronic events from the e
+
e
− annihilation data at the centre-of-mass energies ranging from 60 to 197 GeV were studied. The AMY and OPAL Collaborations
offered a unique opportunity to test QCD by measuring the energy dependence of different observables. The coupling constant,
α
s, was measured by two different methods: first by employing the three-jet observables. Combining all the data, the value of
as at next-to-next leading order (NNLO) was determined to be 0.117 ± 0.004(hard) ± 0.006(theo). Secondly, from the event-shape
distributions, the strong coupling constant, α
s, was extracted at NNLO and it’s evaluation was tested with the energy scale. The results were consistent with the running
of α
s, expected from QCD predictions. Averaging over different observables, α
s was determined to be 0.115 ± 0.007(hard) ± 0.003(theo). 相似文献
5.
Contact-like nonstandard interactions can be revealed only through deviations of observables from the standard model (SM)
predictions. We consider a number of such nonstandard scenarios, and discuss their identification as sources of deviations
in fermion-pair production processes at the international linear collider (ILC), if they were observed. We emphasize the role
of e
− and e
+ polarization in enhancing the identification reaches.
相似文献
6.
Christoph?Ditsche Bastian?Kubis Ulf-G.?Mei?ner 《The European Physical Journal C - Particles and Fields》2009,60(1):83-105
We re-evaluate the electromagnetic corrections to η→3π decays at next-to-leading order in the chiral expansion, arguing that effects of order e
2(m
u
−m
d
) disregarded so far are not negligible compared to other contributions of order e
2 times a light-quark mass. Despite the appearance of the Coulomb pole in η→π
+
π
−
π
0 and cusps in η→3π
0, the overall corrections remain small. 相似文献
7.
《The European Physical Journal C - Particles and Fields》2006,46(1):43-60
High-precision analyses of supersymmetry parameters aim at reconstructing the fundamental supersymmetric theory and its breaking
mechanism. A well defined theoretical framework is needed when higher-order corrections are included. We propose such a scheme,
Supersymmetry Parameter Analysis SPA, based on a consistent set of conventions and input parameters. A repository for computer
programs is provided which connect parameters in different schemes and relate the Lagrangian parameters to physical observables
at LHC and high energy e + e- linear collider experiments, i.e., masses, mixings, decay widths and production cross sections for supersymmetric particles.
In addition, programs for calculating high-precision low energy observables, the density of cold dark matter (CDM) in the
universe as well as the cross sections for CDM search experiments are included. The SPA scheme still requires extended efforts
on both the theoretical and experimental side before data can be evaluated in the future at the level of the desired precision.
We take here an initial step of testing the SPA scheme by applying the techniques involved to a specific supersymmetry reference
point. 相似文献
8.
As B
s
-mesons will be produced abundantly at the LHC, the observability of the flavour-changing-neutral-current decay mode B
s
→ ϕμ+μ− has been studied in CMS at the LHC centre-of-mass energy of 10 TeV. With an integrated luminosity of 100 pb−1, an upper limit of 6.7 × 10−6 on the branching ratio is expected to be obtained. The potential at 7 TeV with a luminosity of 1 fb−1 is expected to be better. 相似文献
9.
The recently discovered narrow peaks (theψ-particles) in e+e− system at 3.105 and 3.695 GeV are interpreted as hadrons in a broken SU4 symmetry scheme. A new additional additive quantum number, parachargeZ, is combined with the usual SU3 quantum numbers in the group SU4. Theψ (3.1) is assigned to a near ideally mixed15⊕1 multiplet of vector mesons (containing theρ) as theI=Y=0, charge conjugationC=−combination ofZ=±1.members. Theψ (3.7) is assigned correspondingly to another mixed15⊕1 multiplet containing theρ′ (1600). The hadronic electromagnetic interactions are modified by the addition of (non-minimal) anomalous pieces that can
changeZ. The decays of theψ-particles are discussed. New enlarged SU4 multiplets of other hadrons are proposed. Tests of our scheme are put forward. The most crucial test will be the observation
of two rather broad resonances in e+ e− collisions with masses around 4.2 GeV and 5.1 GeV. Another prediction is the presence of energetic photons in the decays
of theψ-particles. Important results concerning the recently observed phenomena in the process e+e−→hadrons follow in this scheme. 相似文献
10.
We review high-energy scattering processes that are sensitive to the hadronic structure of the photon, describing theoretical
predictions as well as recent experimental results. These processes include deep-inelastic electron-photon scattering ate
+
e
− colliders; and the production of jets, heavy quarks and isolated photons in the collision of real photons ate
+
e
− colliders, as well as in photon-photon collisions atep colliders. We also comment on minijet based calculations of totalγp andγγ cross-sections, and discuss the possibility that future lineare
+
e
− colliders might produce very large photon fluxes due to the beamstrahlung phenomenon; in the most extreme cases, we predict
more than one hadronicγγ event to occur at every bunch crossing. 相似文献
11.
One-loop electroweak corrections to observables of the reaction e
−
e
− → e
−
e
−(γ) were calculated over a broad range of energies: from conditions of the MOLLER experiment at the Thomas Jefferson Laboratory
(JLab) to those of planned experiments at the International Linear Collider (ILC). The dependence of various contributions
to the observable polarization asymmetry on various renormalization conditions was studied within the scheme of on-shell renormalization.
The results were obtained by two methods: precisely, by applying the FeynArts, FormCalc, LoopTools, and Form computer codes,
and approximately, with the aid of the asymptotic-estimation methods. The resulting compact formulas are absolutely free from
nonphysical parameters and are convenient for deducing numerical estimates. It is shown that the total one-loop correction
is independent of renormalization conditions and takes an identical value within different computational schemes. 相似文献
12.
CP-violating rate asymmetry can be generated in a process only if its amplitude possesses an absorptive part. It is pointed
out that such an absorptive part can be provided ine
+
e
− annihilation by the presence of aZ(Z′) resonance of non-zero width. The CP asymmetry in the process
, wherel
i
are charged leptons, is discussed in several models. In a specific two-Z model, large and observable CP asymmetry ine
+
e
− →τ
+
e
− (τ
−
e
+) is shown to be possible at LEP/SLC energies. 相似文献
13.
Total (elastic+inelastic) cross sections fore
−-O,e
−-O2 ande
−-O3 scattering have been calculated at sample energies between 100 and 1000eV. The basice
−-O atom scattering amplitudes are obtained from the partial wave analysis with a complex optical potential. Thee
−-O2 ande
−-O3 cross-sections are obtained through the independent atom model. Oure
−-O2 cross-sections reproduce the experimental data quite well. Adequate comparisons are made in all the three cases. 相似文献
14.
Catherine Silvestre 《The European Physical Journal C - Particles and Fields》2009,61(4):841-845
In this paper, we calculate the decay rates of the D
+→D
0
e
+
ν, D
S
+→D
0
e
+
ν,
, D
S
+→D
+
e
−
e
+ and B
S
0→B
0
e
−
e
+ semileptonic decay processes, in which only the light quarks decay, while the heavy flavors remain unchanged. The branching
ratios of these decay processes are calculated with the flavor SU(3) symmetry. The uncertainties are estimated by considering
the SU(3) breaking effect. We find that the decay rates are very tiny in the framework of the standard model. We also estimate
the sensitivities of the measurements of these rare decays at future experiments, such as BES-III, super-B and LHC-b. 相似文献
15.
Yu. M. Andreev S. I. Bityukov N. V. Krasnikov A. N. Toropin 《Physics of Atomic Nuclei》2007,70(10):1717-1724
The LHC (CMS) discovery potential in the search for supersymmetry and lepton-flavor violation in neutralino decays using the
e
± μ∓ + E
T
miss
signature is studied. A detailed study is done for the CMS test points LM1-LM9. It is shown that, for the point LM1, it is
possible to detect lepton-flavor violation in neutralino decays with lepton-flavor-violating branching Br(
→ μ±
e
∓
) ≥ 0.04 Br(
→ e
+
e
−
, μ+ μ−
) for an integral luminosity of 10 fb−1. The discovery potential in the mSUGRA-SUSY scenario with tan β = 10, sgn(μ) = + in the (m
0, m
1/2) plane using the e
± μ∓ + E
T
miss
signature is determined.
The text was submitted by the authors in English. 相似文献
16.
Simulation study on ω, ϕ, ρ decays to e
−
e
+ pairs in the ALICE detector for Pb-Pb collisions at LHC energy was performed. The possibility of selecting resonance signals
over the combinatorial backgrounds is demonstrated using the realistic simulation tracking and particle identification algorithms
of the ALICE offline framework (AliRoot). Results for J/ψ are presented also for comparison. 相似文献
17.
Lorenzo Basso Stefano Moretti Giovanni Marco Pruna 《The European Physical Journal C - Particles and Fields》2011,71(8):1724
We investigate the phenomenology of the Higgs sector of the minimal B−L extension of the Standard Model at a future e
+
e
− Linear Collider. We consider the discovery potential of both a sub-TeV and a multi-TeV machine. We show that, within such
a theoretical scenario, several novel production and decay channels involving the two physical Higgs states, precluded at
the LHC, could experimentally be accessed at such machines. Amongst these, several Higgs signatures have very distinctive
features with respect to those of other models with enlarged Higgs sector, as they involve interactions of Higgs bosons between
themselves, with Z′ bosons as well as with heavy neutrinos. In particular, we present the scope of the Z′ strahlung process for single and double Higgs production, the only suitable mechanism enabling one to access an almost decoupled
heavy scalar state (therefore outside the LHC range). 相似文献
18.
R. H. K. Kadala P. G. Mercadante J. K. Mizukoshi Xerxes Tata 《The European Physical Journal C - Particles and Fields》2008,56(4):511-528
The branching fraction for the decays of gluinos to third generation quarks is expected to be enhanced in classes of supersymmetric
models where either third generation squarks are lighter than other squarks, or in mixed-higgsino dark matter models constructed
so as to be in concordance with the measured density of cold dark matter. In such scenarios, gluino production events at the
CERN Large Hadron Collider should be rich in top and bottom quark jets. Requiring b jets in addition to E
T
miss should, therefore, enhance the supersymmetry signal relative to Standard Model backgrounds from V + jet, VV and QCD backgrounds (V=W,Z). We quantify the increase in the supersymmetry reach of the LHC from b-tagging in a variety of well-motivated models of supersymmetry. We also explore “top tagging” at the LHC. We find that while
the efficiency for this turns out to be too low to give an increase in reach beyond that obtained via b-tagging, top tagging can indeed provide a confirmatory signal if gluinos are not too heavy. We also examine c jet tagging but find that it is not useful at the LHC. Finally, we explore the prospects for detecting the direct production
of third generation squarks in models with an inverted squark mass hierarchy. This is signaled by b jets + E
T
miss events being harder than in the Standard Model, but softer than those from the production of gluinos and heavier squarks.
We find that while these events can be readily separated from the SM background (for third generation squark masses ∼300–500 GeV),
the contamination from the much heavier gluinos and squarks remains formidable if these are also accessible. 相似文献
19.
J.?G.?Due?as N.?Gutierrez R.?Martínez F.?Ochoa 《The European Physical Journal C - Particles and Fields》2009,60(4):653-659
We analyse the possibilities to detect a new Z
′ boson in di-electron events at Tevatron and LHC in the framework of the 331 model with right-handed neutrinos. We also study
other fermions and Higgs events as final state at LHC. Using
collision data collected by the CDF II detector at Fermilab Tevatron, we find that the 331 Z
′ boson is excluded with masses below 920 GeV. For an integrated luminosity of 100 fb−1 at LHC, and considering a central value
GeV, we obtain the invariant-mass distribution in the process pp→Z
′→e
+
e
−, where a huge peak, corresponding to 800 signal events/(20 GeV), is found above the SM background. The number of di-electron
events vary from 50000 to 2400 in the mass range of
–2000 GeV. We also obtain branching ratios and cross sections in other fermion and Higgs channels at LHC, where a heavy top
quark T exhibits the biggest ratio with m
T
=300 GeV. 相似文献
20.
B. Cameron Reed 《Central European Journal of Physics》2005,3(1):1-7
The ground-state energy of neutral helium is estimated variationally with a trial wavefunction of the form ϕ≈e
−γ(rA/a
o)ne−γ(rB/a
o)n. This model represents a modification of traditional textbook examinations of this problem via inclusion of the power “n”
as a second nonlinear variational parameter in addition to the usual effective nuclear charge γ and leads to an upper-limit
on the ground state energy of −2.86107 E
h
(E
h
=1 hartree) in comparison with the traditional (n=1) result of −2.84766 E
h
. This result represents a reduction of the percentage overestimate from the true ground-state energy (−2.90373 E
h
) of from 1.93 to 1.47. In comparison with the maximum accuracy obtainable from an uncorrelated trial wavefunction, −2.86168
E
h
, the present trial wavefunction reduces the percentage overestimate from 0.49 (n=1) to 0.021. The optimum values of (n, γ)
are determined to be ≈(0.897, 1.825). 相似文献