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preprint2015arXiv

Signatures of Large Composite Dark Matter States

We investigate the interactions of large composite dark matter (DM) states with the Standard Model (SM) sector. Elastic scattering with SM nuclei can be coherently enhanced by factors as large as A^2, where A is the number of constituents in the composite state (there exist models in which DM states of very large A > 10^8 may be realised). This enhancement, for a given direct detection event rate, weakens the expected signals at colliders by up to 1/A. Moreover, the spatially extended nature of the DM states leads to an additional, characteristic, form factor modifying the momentum dependence of scattering processes, altering the recoil energy spectra in direct detection experiments. In particular, energy recoil spectra with peaks and troughs are possible, and such features could be confirmed with only O(50) events, independently of the assumed halo velocity distribution. Large composite states also generically give rise to low-energy collective excitations potentially relevant to direct detection and indirect detection phenomenology. We compute the form factor for a generic class of such excitations - quantised surface modes - finding that they can lead to coherently-enhanced, but generally sub-dominant, inelastic scattering in direct detection experiments. Finally, we study the modifications to capture rates in astrophysical objects that follow from the elastic form factor, as well as the effects of inelastic interactions between DM states once captured. We argue that inelastic interactions may lead to the DM collapsing to a dense configuration at the centre of the object.

preprint2013arXiv

The Construction of Dual-trace Factor in Yang-Mills Theory

Recently, a BCJ dual of the color-ordered formula for Yang-Mills amplitude was proposed, where the dual-trace factor satisfies cyclic symmetry and KK-relation. In this paper, we present a systematic construction of the dual-trace factor based on its proposed relations to kinematic numerators in dual-DDM form. We show that the construction presented respects relabeling symmetry. In addition, we show that using relabeling symmetry as conditions, the same construction can be solved independently.

preprint2012arXiv

Single Spin Asymmetry through QCD Instantons

We revisit the effects of QCD instantons in semi-inclusive deep inelastic scattering (SIDIS). We show that large single spin asymmetry (SSA) effects can be induced in longitudinally and transversely polarized proton targets. The results are in agreement with most of the reported data for pion and kaon production. The same effects are found to be important in polarized proton on proton scattering for both charged and chargeless pion productions. The results agree with the reported data in a wide range of \sqrt{s} = 19.4-200 GeV. We predict the SSA for π^\pm production in p_\uparrow p in the collider range of \sqrt{s} = 62.4-500 GeV. The backward π^{\pm} and π^0 productions for the SSA in p_\uparrow p collisions are predicted to coincide at large \sqrt{s}.

preprint2015arXiv

Spin Physics through QCD Instantons

We review some aspects of spin physics where QCD instantons play an important role. In particular, their large contributions in semi-inclusive deep-inelastic scattering and polarized proton on proton scattering. We also review their possible contribution in the $\mathcal{P}$-odd pion azimuthal charge correlations in peripheral $AA$ scattering at collider energies.

preprint2015arXiv

NJL model approach to diquarks and baryons in quark matter

We describe baryons as quark-diquark bound states at finite temperature and density within the NJL model for chiral symmetry breaking and restoration in quark matter. Based on a generalized Beth-Uhlenbeck approach to mesons and diquarks we present in a first step the thermodynamics of quark-diquark matter which includes the Mott dissociation of diquarks at finite temperature. In a second step we solve the Bethe-Salpeter equation for the baryon as a quark-diquark bound state in quark-diquark matter. We obtain a stable, bound baryon even beyond the Mott temperature for diquark dissociation since the phase space occupation effect (Pauli blocking for quarks and Bose enhancement for diquarks) in the Bethe-Salpeter kernel for the nucleon approximately cancel so that the nucleon mass follows the in-medium behaviour of the quark and diquark masses towards chiral restoration. In this situation the baryon is obtained as a "borromean" three-quark state in medium because the two-particle state (diquark) is unbound while the three-particle state (baryon) is bound.

preprint2014arXiv

P-Odd Pion Azimuthal Charge Correlations in Heavy Ion Collisions

We argue that the large instanton induced Pauli form factor in polarized proton-proton scattering may cause, through topological fluctuations, substantial charge-dependent azimuthal correlations for pi^+/pi^- production in peripheral heavy ion collisions both at RHIC and LHC, thanks to the large induced magnetic field. Our results compare favorably to the measured pion azimuthal correlations by the STAR and ALICE collaborations.

preprint2012arXiv

Modified perturbation theory for angular distribution in W-pair production

We examine the capabilities of the modified perturbation theory (MPT) for description of $W$-pair production and decay in $e^{+} e^{-}$ annihilation. In a model with Dyson-resummed propagators of unstable particles, we calculate even and odd contributions to the distribution in the cosine of the $W^{-}$ production angle relative to the $e^{-}$ beam. On comparing the results of calculations in the NNLO approximation of MPT with the exact results in the model, a coincidence of outcomes at the ILC energies is detected at the per-mille level.

preprint2015arXiv

Non-perturbative QCD effects in forward scattering at LHC

We study infrared contributions to semihard parton-parton interactions by considering an effective charge whose finite infrared behavior is constrained by a dynamical mass scale. Using an eikonal QCD-based model in order to connect this semihard parton-level dynamics to the hadron-hadron scattering, we obtain predictions for the proton-proton ($pp$) and antiproton-proton ($\bar{p}p$) total cross sections, $σ_{tot}^{pp,\bar{p}p}$, and the ratios of the real to imaginary part of the forward scattering amplitude, $ρ^{pp,\bar{p}p}$. We discuss the theoretical aspects of this formalism and consider the phenomenological implications of a class of energy-dependent form factors in the high-energy behavior of the forward amplitude. We introduce integral dispersion relations specially tailored to relate the real and imaginary parts of eikonals with energy-dependent form factors. Our results, obtained using a group of updated sets of parton distribution functions (PDFs), are consistent with the recent data from the TOTEM, AUGER and Telescope Array experiments.

preprint2015arXiv

Topologically Stratified Energy Minimizers in a Product Abelian Field Theory

We study a recently developed product Abelian gauge field theory by Tong and Wong hosting magnetic impurities. We first obtain a necessary and sufficient condition for the existence of a unique solution realizing such impurities in the form of multiple vortices. We next reformulate the theory into an extended model that allows the coexistence of vortices and anti-vortices. The two Abelian gauge fields in the model induce two species of magnetic vortex-lines resulting from $N_s$ vortices and $P_s$ anti-vortices ($s=1,2$) realized as the zeros and poles of two complex-valued Higgs fields, respectively. An existence theorem is established for the governing equations over a compact Riemann surface $S$ which states that a solution with prescribed $N_1, N_2$ vortices and $P_1,P_2$ anti-vortices of two designated species exists if and only if the inequalities \[ \left|N_1+N_2-(P_1+P_2)\right|<\frac{|S|}π,\quad \left|N_1+2N_2-(P_1+2P_2)\right|<\frac{|S|}π, \] hold simultaneously, which give bounds for the `differences' of the vortex and anti-vortex numbers in terms of the total surface area of $S$. The minimum energy of these solutions is shown to assume the explicit value \[ E= 4π(N_1+N_2+P_1+P_2), \] given in terms of several topological invariants, measuring the total tension of the vortex-lines.

preprint2013arXiv

Parton distributions with QED corrections

We present a set of parton distribution functions (PDFs), based on the NNPDF2.3 set, which includes a photon PDF, and QED contributions to parton evolution. We describe the implementation of the combined QCD+QED evolution in the NNPDF framework. We then provide a first determination of the full set of PDFs based on deep-inelastic scattering data and LHC data for W and Z/gamma* Drell-Yan production, using leading-order QED and NLO or NNLO QCD. We compare the ensuing NNPDF2.3QED PDF set to the older MRST2004QED set. We perform a preliminary investigation of the phenomenological implications of NNPDF2.3QED: specifically, photon-induced corrections to direct photon production at HERA, and high-mass dilepton and W pair production at the LHC.

preprint2013arXiv

Construction of an effective Yang-Mills Lagrangian with manifest BCJ duality

The BCJ decomposition is a highly non-trivial property of gauge theories. In this paper we systematically construct an effective Lagrangian, whose Feynman rules automatically produce the BCJ numerators. The effective Lagrangian contains non-local terms. The difference between the standard Yang-Mills Lagrangian and the effective Lagrangian simplifies to zero.

preprint2016arXiv

The Corolla Polynomial for spontaneously broken Gauge Theories

In [1, 2, 3] the Corolla Polynomial $ \mathcal C (Γ) \in \mathbb C [a_{h_1}, \ldots, a_{h_{\left \vert Γ^{[1/2]} \right \vert}}] $ was introduced as a graph polynomial in half-edge variables $ \left \{ a_h \right \} _{h \in Γ^{[1/2]}} $ over a 3-regular scalar quantum field theory (QFT) Feynman graph $ Γ$. It allows for a covariant quantization of pure Yang-Mills theory without the need for introducing ghost fields, clarifies the relation between quantum gauge theory and scalar QFT with cubic interaction and translates back the problem of renormalizing quantum gauge theory to the problem of renormalizing scalar QFT with cubic interaction (which is super renormalizable in 4 dimensions of spacetime). Furthermore, it is, as we believe, useful for computer calculations. In [4] on which this paper is based the formulation of [1, 2, 3] gets slightly altered in a fashion specialized in the case of the Feynman gauge. It is then formulated as a graph polynomial $ \mathcal C ( Γ) \in \mathbb C [a_{h_{1 \pm}}, \ldots, a_{h_{\left \vert Γ^{[1/2]} \right \vert} \vphantom{h}_\pm}, b_{h_1}, \ldots, b_{h_{\left \vert Γ^{[1/2]} \right \vert}}] $ in three different types of half-edge variables $ \left \{ a_{h_+} , a_{h_-} , b_h \right \} _{h \in Γ^{[1/2]}} $. This formulation is also suitable for the generalization to the case of spontaneously broken gauge theories (in particular all bosons from the Standard Model), as was first worked out in [4] and gets reviewed here.

preprint2004arXiv

Neutrino quantum states in matter

We propose a modified Dirac equation for a massive neutrino moving in the presence of the background matter. The effects of the charged and neutral-current interactions with the matter as well as the matter motion and polarization are accounted for. In the particular case of the matter with a constant density the exact solutions of this equation are found, the neutrino energy spectrum in the matter is also determined. On this basis the effects of the neutrino trapping and reflection, the neutrino-antineutrino pair annihilation and creation in a medium are studied. The quantum theory of the spin light of neutrino in matter ($SLν$) is also developed.

preprint2006arXiv

Relaxed constraints on neutrino oscillation parameters

We study the cosmological constraints on active-sterile neutrino oscillations nu_e <-> nu_s for the case when nu_s is partially filled initially, i.e. 0 < delta N_s < 1. We provide numerical analysis of the cosmological production of He-4, in the presence of nu_e <-> nu_s oscillations, effective after neutrino decoupling, accounting for all known oscillations effects on cosmological nucleosynthesis. Cosmological constraints on oscillation parameters corresponding to higher than 5% He-4 overproduction and different non-zero initial populations of the sterile state delta N_s < 1 are calculated. These generalized cosmological constraints corresponding to delta N_s > 0 are relaxed in comparison with the delta N_s = 0 case and the relaxation is proportional to delta N_s.

preprint2003arXiv

A Cicerone for the Physics of Charm

After briefly recapitulating the history of the charm quantum number we sketch the experimental environments and instruments employed to study the behaviour of charm hadrons and then describe the theoretical tools for treating charm dynamics. We discuss a wide range of inclusive production processes before analyzing the spectroscopy of hadrons with hidden and open charm and the weak lifetimes of charm mesons and baryons. Then we address leptonic, exclusive semileptonic and nonleptonic charm decays. Finally we treat $D^0 - \bar D^0$ oscillations and CP (and CPT) violation before concluding with some comments on charm and the quark-gluon plasma. We will make the case that future studies of charm dynamics -- in particular of CP violation -- can reveal the presence of New Physics. The experimental sensitivity has only recently reached a level where this could reasonably happen, yet only as the result of dedicated efforts. This review is meant to be both a pedagogical introduction for the young scholar and a useful reference for the experienced researcher. We aim for a self-contained description of the fundamental features while providing a guide through the literature for more technical issues.

preprint2015arXiv

FIESTA 4: optimized Feynman integral calculations with GPU support

This paper presents a new major release of the program FIESTA (Feynman Integral Evaluation by a Sector decomposiTion Approach). The new release is mainly aimed at optimal performance at large scales when one is increasing the number of sampling points in order to reduce the uncertainty estimates. The release now supports graphical processor units (GPU) for the numerical integration, methods to optimize cluster-usage, as well as other speed, memory, and stability improvements.

preprint2011arXiv

W-pair production in modified perturbation theory

We examine capabilities of the modified perturbation theory (MPT) for description of the processes with productions and decays of fundamental unstable particles. We calculate total cross-section for $e^{+} e^{-} \to γ,Z \to W^{+} W^{-} \to 4f$ in a model with the Dyson-resummed and with the MPT-expanded up to the NNLO Breit-Wigner factors, and compare the outcomes. At the ILC energies a coincidence of the outcomes is detected with precision better than one per-mille.

preprint2009arXiv

Could Leptons, Quarks or both be Highly Relativistic Bound States of Minimally Interacting Fermion and Scalar?

The possibility that leptons, quarks or both might be highly relativistic bound states of a spin-0 and spin-1/2 constituent bound by minimal electrodynamics is discussed. Typically, strongly bound solutions of the Bethe-Salpeter equation exist only when the coupling constant is on the order of or greater than unity. For the bound-state system discussed here, there exist two classes of boundary conditions that could yield strongly bound solutions with coupling constants on the order of the electromagnetic fine structure constant. In both classes the bound state must have spin one half, thus providing a possible explanation for the absence of higher-spin leptons and quarks.

preprint2013arXiv

Rivet user manual

This is the manual and user guide for the Rivet system for the validation and tuning of Monte Carlo event generators for high energy physics. As well as the core Rivet library, this manual describes the usage of the rivet program and the AGILe generator interface library. The depth and level of description is chosen for users of the system, starting with the basics of using validation code written by others, and then covering sufficient details to write new Rivet analyses and calculational components.

preprint2016arXiv

The coherent cross section of vector mesons in ultraperipheral PbPb collisions at the LHC

The coherent cross section of $J/ψ$, $ρ$, $ϕ$ are computed in dipole model in the ultraperipheral PbPb collisions, the IP-Sat and IIM model are applied in the calculation of the differential cross section of the dipole scattering off the nucleon, three kinds of forward vector meson wave functions are used in the overlap. The prediction of $J/ψ$ and $ρ$ is compared with the experimental data of the ALICE Collaboration, and the prediction of $ϕ$ is also given in this paper.

preprint2016arXiv

Curvature-Restored Gauge Invariance and Ultraviolet Naturalness

It is shown that, $(a Λ^2 + b |H|^2)R$ in a spacetime of curvature $R$ is a natural ultraviolet $(U\!V)$ completion of $(a Λ^4 + b Λ^2 |H|^2)$ in the flat-spacetime Standard Model $(S\!M)$ with Higgs field $H$, $U\!V$ scale $Λ$ and loop factors $a$, $b$. This curvature completion rests on the fact that a $Λ$-mass gauge theory in flat spacetime turns, on the cut-view $R = 4 Λ^2$, into a massless gauge theory in curved spacetime. It provides a symmetry reason for curved spacetime, wherein gravity and matter are both low-energy effective phenomena. Gravity arises correctly if new physics exists with at least 63 more bosons than fermions, with no need to interact with the $S\!M$ and with dark matter as a natural harbinger. It can source various cosmological, astrophysical and collider phenomena depending on its spectrum and couplings to the $S\!M$.

preprint2015arXiv

Big Bang Synthesis of Nuclear Dark Matter

We investigate the physics of dark matter models featuring composite bound states carrying a large conserved dark "nucleon" number. The properties of sufficiently large dark nuclei may obey simple scaling laws, and we find that this scaling can determine the number distribution of nuclei resulting from Big Bang Dark Nucleosynthesis. For plausible models of asymmetric dark matter, dark nuclei of large nucleon number, e.g. > 10^8, may be synthesised, with the number distribution taking one of two characteristic forms. If small-nucleon-number fusions are sufficiently fast, the distribution of dark nuclei takes on a logarithmically-peaked, universal form, independent of many details of the initial conditions and small-number interactions. In the case of a substantial bottleneck to nucleosynthesis for small dark nuclei, we find the surprising result that even larger nuclei, with size >> 10^8, are often finally synthesised, again with a simple number distribution. We briefly discuss the constraints arising from the novel dark sector energetics, and the extended set of (often parametrically light) dark sector states that can occur in complete models of nuclear dark matter. The physics of the coherent enhancement of direct detection signals, the nature of the accompanying dark-sector form factors, and the possible modifications to astrophysical processes are discussed in detail in a companion paper.

preprint2015arXiv

Properties of light (anti)nuclei and (anti) hypertriton production in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 TeV

We investigate the properties of light (anti)nuclei and (anti)hypertriton production in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}=2.76$ TeV, based on the parton and hadron cascade and dynamically constrained phase-space coalescence (PACIAE + DCPC) model. We found that the yields of light (anti)nuclei and (anti)hypertriton strongly depend on the centrality, i.e., their yields decrease rapidly with the increase of centrality bins, but their yield ratios are independent of centrality. The results of theoretical model are well consistent with ALICE data. Furthermore, we found that the integrated yields of (anti)nuclei per participant nucleon increase from peripheral to central collisions more rapidly with increasing mass number. The transverse momentum distributions of $\overline{_{\overlineΛ}^3 H}, {_Λ^3 H},{\overline{^3 He}}$ and $^3{He}$ are also discussed in the 0-10% most central Pb-Pb collisions.The coalescence parameters $B_A$ of light (anti)nuclei and (anti)hypernuclei are analyzed.

preprint2015arXiv

Stretched String with Self-Interaction at High Resolution: Spatial Sizes and Saturation

We model the (holographic) QCD Pomeron as a long and stretched (fixed impact parameter) transverse quantum string in flat $D_\perp=3$ dimensions. After discretizing the string in $N$ string bits, we analyze its length, mass and spatial distribution for large $N$ or low-x ($x=1/N$), and away from its Hagedorn point. The string bit distribution shows sizable asymmetries in the transverse plane that may translate to azimuthal asymmetries in primordial particle production in the Pomeron kinematics, and the flow moments in minimum bias $pp$ and $pA$ events. At moderately low-x and relatively small string self-interactions $g_s\approx α_s$ (the gauge coupling), a pre-saturation phase is identified whereby the string transverse area undergoes a sharp transition from a large diffusive growth to a small fixed size area set by few string lengths $l_s$. For lower values of $x$ the transverse string bit density is shown to increase as $1/x$ before saturating at the Bekenstein bound of one bit per Planck area with the Planck length $l_P/l_s\approx α_s^{2/3}$. We argue that the effects of the AdS$_5$ curvature on the interacting string maybe estimated using an effective transverse dimension between the interacting string bits. The result is a smoother transition with a transverse string bit density increasing as $1/x^{0.31}$.