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Vector Boson Production in Association with a Jet at Forward Rapidities
http://cds.cern.ch/record/2659446
Final states with a vector boson and a hadronic jet allow one to infer the Born-level kinematics of the underlying hard scattering process, thereby probing the partonic structure of the colliding protons. At forward rapidities, the parton collisions are highly asymmetric and resolve the parton distributions at very large or very small momentum fractions, where they are less well constrained by other processes. Using theory predictions accurate to next-to-next-to-leading order (NNLO) in QCD for both $\mathrm{W}^{\pm}$ and $\mathrm{Z}$ production in association with a jet at large rapidities at the LHC, we perform a detailed phenomenological analysis of recent LHC measurements. The increased theory precision allows us to clearly identify specific kinematical regions where the description of the data is insufficient. By constructing ratios and asymmetries of these cross sections, we aim to identify possible origins of the deviations, and highlight the potential impact of the data on improved determinations of parton distributions.Gehrmann-De Ridder, A.Gehrmann, T.Glover, E.W.N.Huss, A.Walker, D.M.Sun, 17 Feb 2019 03:30:08 GMT2019-01-30arXiv:1901.11041http://cds.cern.ch/record/2659446['arXiv:1901.11041']arXiv:1901.11041Theoretical aspects of antimatter and gravity
http://cds.cern.ch/record/2659391
In this short contribution, I review the physical case of studying the gravitational properties of antimatter from a theoretical perspective. I first discuss which elements are desirable for any theory where the long-range interactions between matter and antimatter differ from those of matter with itself. Afterwards I describe the standard way to hide the effects of new forces in matter–matter interactions which still allows one to generate ponderable matter–antimatter interactions. Finally, I comment on some recent ideas and propose some possible future directions.Blas, DiegoSat, 16 Feb 2019 05:25:24 GMThttp://cds.cern.ch/record/2659391['']Searching in CMS Open Data for Dimuon Resonances with Substantial Transverse Momentum
http://cds.cern.ch/record/2658223
We study dimuon events in 2.11/fb of 7 TeV pp collisions, using CMS Open Data, and search for a narrow dimuon resonance with moderate mass (14-66 GeV) and substantial transverse momentum (pT). Applying dimuon pT cuts of 25 GeV and 60 GeV, we explore two overlapping samples: one with isolated muons, and one with prompt muons without an isolation requirement. Using the latter sample requires information about detector effects and QCD backgrounds, which we obtain directly from the CMS Open Data. We present model-independent limits on the product of cross section, branching fraction, acceptance, and efficiencies. These limits are stronger, relative to a corresponding inclusive search without a pT cut, by factors of as much as nine. Our "pT-enhanced" dimuon search strategy provides improved sensitivity to models in which a new particle is produced mainly in the decay of something heavier, as could occur, for example, in decays of the Higgs boson or of a TeV-scale top partner. An implementation of this method with the current 13 TeV data should improve the sensitivity to such signals further by roughly an order of magnitude.Cesarotti, CariSoreq, YotamStrassler, Matthew J.Thaler, JesseXue, WeiThu, 14 Feb 2019 04:03:00 GMT2019-02-11arXiv:1902.04222http://cds.cern.ch/record/2658223['arXiv:1902.04222']arXiv:1902.04222Co-Scattering Dark Matter
http://cds.cern.ch/record/2657691
We propose a novel mechanism that, in two-component dark matter models, the subdominant one can thermalize the dominant one in galaxies, and leads to core density profiles. We take ultralight dark photons and $\mathrm{GeV}$-$\mathrm{TeV}$ Dirac fermions as an example, with a $U(1)$ coupling between the two dark matter candidates. This mechanism is significantly different from the self-interacting dark matter, due to three effects: 1) large occupation number enhancement, 2) forward-backward scattering cancellation, and 3) multiple scatterings required for the heavy dark matter. Unlike the fuzzy dark matter solution to the small structure problems having tension with Lyman-$\alpha$, the ultralight dark photons with mass $\gtrsim 10^{-21}$ eV can have a core profile through interactions with $\psi$ and are not constrained by other astrophysical observations.Liu, JiaWang, Xiao-PingXue, WeiSat, 09 Feb 2019 03:27:47 GMT2019-02-06arXiv:1902.02348http://cds.cern.ch/record/2657691['arXiv:1902.02348']arXiv:1902.02348Analytic results for color-singlet production at NNLO QCD with the nested soft-collinear subtraction scheme
http://cds.cern.ch/record/2657591
We present analytic formulas that describe fully-differential production of color-singlet final states in $q\bar q$ and $gg$ annihilation, including all the relevant partonic channels, through NNLO QCD. We work within the nested soft-collinear scheme which allows for fully local subtraction of infrared divergences. We demonstrate analytic cancellation of soft and collinear poles and present formulas for finite parts of all integrated subtraction terms. These results provide an important building block for calculating NNLO QCD corrections to arbitrary processes at hadron colliders within the nested soft-collinear subtraction scheme.Caola, FabrizioMelnikov, KirillRöntsch, RaoulFri, 08 Feb 2019 03:08:13 GMT2019-02-06arXiv:1902.02081http://cds.cern.ch/record/2657591['arXiv:1902.02081']arXiv:1902.02081Full NLO corrections to 3-jet production and R32 at the LHC
http://cds.cern.ch/record/2657126
We present the evaluation of the complete set of NLO corrections to three-jet production at the LHC. To this end we consider all contributions of $\mathcal{O}(\alpha_s^n\alpha^m)$ with $n+m=3$ and $n+m=4$. This includes in particular also subleading Born contributions of electroweak origin, as well as electroweak virtual and QED real-radiative corrections. As an application we present results for the three- over two-jet ratio $R_{32}$. While the impact of non-QCD corrections on the total cross section is rather small, they can exceed $-10\%$ for high jet transverse momenta. The $R_{32}$ observable turns out to be very stable against electroweak corrections, receiving absolute corrections below $5\%$ even in the high-$p_T$ region.Reyer, MaxSchönherr, MarekSchumann, SteffenThu, 07 Feb 2019 03:02:56 GMT2019-02-05arXiv:1902.01763http://cds.cern.ch/record/2657126['arXiv:1902.01763']arXiv:1902.01763Probing ALPs and the Axiverse with Superconducting Radiofrequency Cavities
http://cds.cern.ch/record/2657125
Axion-like particles (ALPs) with couplings to electromagnetism have long been postulated as extensions to the Standard Model. String theory predicts an "axiverse" of many light axions, some of which may make up the dark matter in the universe and/or solve the strong CP problem. We propose a new experiment using superconducting radiofrequency (SRF) cavities which is sensitive to light ALPs independent of their contribution to the cosmic dark matter density. Off-shell ALPs will source cubic nonlinearities in Maxwell's equations, such that if a SRF cavity is pumped at frequencies $\omega_1$ and $\omega_2$, in the presence of ALPs there will be power in modes with frequencies $2\omega_1 \pm \omega_2$. Our setup is similar in spirit to light-shining-through-walls (LSW) experiments, but because the pump field itself effectively converts the ALP back to photons inside a single cavity, our sensitivity scales differently with the strength of the external fields, allowing for superior reach as compared to experiments like OSQAR while utilizing current technology. Furthermore, a well-defined program of increasing sensitivity has a guaranteed physics result: the first observation of the Euler-Heisenberg term of low-energy QED at energies below the electron mass. We discuss how the ALP contribution may be separated from the QED contribution by a suitable choice of pump modes and cavity geometry, and conclude by describing the ultimate sensitivity of our proposed program of experiments to ALPs.Bogorad, ZacharyHook, AnsonKahn, YonatanSoreq, YotamThu, 07 Feb 2019 03:02:52 GMT2019-02-04arXiv:1902.01418http://cds.cern.ch/record/2657125['arXiv:1902.01418']arXiv:1902.01418Soft gravitational radiation from ultra-relativistic collisions at sub- and sub-sub-leading order
http://cds.cern.ch/record/2655428
Using soft-graviton theorems a well-known zero-frequency limit (ZFL) for the gravitational radiation flux $dE^{GW}/d \omega$ is re-derived and extended to order ${{\cal O}}(\omega)$ and ${{\cal O}}(\omega^2)$ for arbitrary massless multi-particle collisions. The (angle-integrated, unpolarized) ${{\cal O}}(\omega)$ correction to the flux turns out to be absent in the case of two-particle elastic collisions. The ${{\cal O}}(\omega^2)$ correction is instead non-vanishing and takes a simple general expression which is then applied to bremsstrahlung from two-particle elastic collisions. For a tree-level process the outcome is finite and consistent with expectations. Instead, if the tree-level form of the soft theorems is used at sub-sub-leading order even when the elastic amplitude needs an all-loop (eikonal) resummation, an unphysical infrared singularity occurs. Its origin can be traced to the infinite Coulomb phase of gravitational scattering in four dimensions. We briefly discuss how to get rid, in principle, of the unwanted divergences and indicate --without carrying out-- a possible procedure to find the proper correction to the naive soft theorems. Nevertheless, if a simple recipe recently proposed for handling these divergences is adopted, we find surprisingly good agreement with results obtained independently via the eikonal approach to transplanckian-energy scattering at large (small) impact parameter (deflection angle), where such Coulomb divergences explicitly cancel out.Addazi, AndreaBianchi, MassimoVeneziano, GabrieleFri, 01 Feb 2019 03:51:57 GMT2019-01-30arXiv:1901.10986http://cds.cern.ch/record/2655428['arXiv:1901.10986']arXiv:1901.10986NLL${'}$ resummation of jet mass
http://cds.cern.ch/record/2655224
Starting from a factorization theorem in effective field theory, we present resummed results for two non-global observables: the invariant-mass distribution of jets and the energy distribution outside jets. Our results include the full next-to-leading-order corrections to the hard, jet and soft functions and are implemented in a parton-shower framework which generates the renormalization-group running in the effective theory. The inclusion of these matching corrections leads to an improved description of the data and reduced theoretical uncertainties. They will have to be combined with two-loop running in the future, but our results are an important first step towards the higher-logarithmic resummation of non-global observables.Balsiger, MarcelBecher, ThomasShao, Ding YuWed, 30 Jan 2019 03:02:27 GMT2019-01-25arXiv:1901.09038http://cds.cern.ch/record/2655224['arXiv:1901.09038']arXiv:1901.09038A Monte Carlo global analysis of the Standard Model Effective Field Theory: the top quark sector
http://cds.cern.ch/record/2654632
We present a novel framework for carrying out global analyses of the Standard Model Effective Field Theory (SMEFT) at dimension-six: SMEFiT. This approach is based on the Monte Carlo replica method for deriving a faithful estimate of the experimental and theoretical uncertainties and enables one to construct the probability distribution in the space of the SMEFT degrees of freedom. As a proof of concept of the SMEFiT methodology, we present a first study of the constraints on the SMEFT provided by top quark production measurements from the LHC. Our analysis includes more than 30 independent measurements from 10 different processes at 8 and 13 TeV such as inclusive top-quark pair and single-top production and the associated production of top quarks with weak vector bosons and the Higgs boson. State-of-the-art theoretical calculations are adopted both for the Standard Model and for the SMEFT contributions, where in the latter case NLO QCD corrections are included for the majority of processes. We derive bounds for the 34 degrees of freedom relevant for the interpretation of the LHC top quark data and compare these bounds with previously reported constraints. Our study illustrates the significant potential of LHC precision measurements to constrain physics beyond the Standard Model in a model-independent way, and paves the way towards a global analysis of the SMEFT.Hartland, Nathan P.Maltoni, FabioNocera, Emanuele R.Rojo, JuanSlade, EmmaVryonidou, EleniZhang, CenWed, 23 Jan 2019 03:40:43 GMT2019-01-17arXiv:1901.05965http://cds.cern.ch/record/2654632['arXiv:1901.05965']arXiv:1901.05965BE-HaPPY: Bias Emulator for Halo Power Spectrum including massive neutrinos
http://cds.cern.ch/record/2654550
We study the clustering properties of dark matter halos in real- and redshift-space in cosmologies with massless and massive neutrinos through a large set of state-of-the-art N-body simulations. We provide quick and easy-to-use prescriptions for the halo bias on linear and mildly non-linear scales, both in real and redshift space, which are valid also for massive neutrinos cosmologies. Finally we present a halo bias emulator,$\textbf{BE-HaPPY}$, calibrated on the N-body simulations, which is fast enough to be used in the standard Markov Chain Monte Carlo approach to cosmological inference. For a fiducial standard $\Lambda$CDM cosmology $\textbf{BE-HaPPY}$ provides percent or sub-percent accuracy on the scales of interest (linear and well into the mildly non-linear regime), meeting therefore for the halo-bias the accuracy requirements for the analysis of next-generation large--scale structure surveys.Valcin, DavidVillaescusa-Navarro, FranciscoVerde, LiciaRaccanelli, AlviseTue, 22 Jan 2019 03:07:49 GMT2019-01-17arXiv:1901.06045http://cds.cern.ch/record/2654550['arXiv:1901.06045']arXiv:1901.06045Reactor neutrino oscillations as constraints on Effective Field Theory
http://cds.cern.ch/record/2654129
We study constraints on the Standard Model Effective Field Theory (SMEFT) from neutrino oscillations in short-baseline reactor experiments. We calculate the survival probability of reactors antineutrinos at the leading order in the SMEFT expansion, that is including linear effects of dimension-6 operators. It is shown that, at this order, reactor experiments alone cannot probe charged-current contact interactions between leptons and quarks that are of the (pseudo)vector (V$\pm$A) or pseudo-scalar type. We also note that flavor-diagonal (pseudo)vector coefficients do not have observable effects in oscillation experiments. In this we reach novel or different conclusions than prior analyses of non-standard neutrino interactions. On the other hand, reactor experiments offer a unique opportunity to probe tensor and scalar SMEFT operators that are off-diagonal in the lepton-flavor space. We derive constraints on the corresponding SMEFT parameters using the most recent data from the Daya Bay and RENO experiments.Falkowski, AdamGonzález-Alonso, MartínTabrizi, ZahraThu, 17 Jan 2019 03:45:21 GMT2019-01-14arXiv:1901.04553http://cds.cern.ch/record/2654129['arXiv:1901.04553']arXiv:1901.04553Thermal width of the Higgs boson in hot QCD matter
http://cds.cern.ch/record/2654127
Following Caron-Huot and combining results for the thermal dependence of spectral functions at large time-like momenta, we write an explicit expression for the thermal width of the Higgs boson to $\mathcal{O}(\alpha_\mathrm{s})$ for $T \ll M_H$. It is an $\mathcal{O}( \alpha_\mathrm{s} (T/M_H)^4 )$ correction for $H\to gg$ and $H\to q\bar{q}$. We also compile corresponding results for the thermal width of the $Z$-boson, and we recall which generic structures of the field theory, accessible via the operator product expansion, fix the $T/M$-dependence of the decay of heavy particles.Ghiglieri, JacopoWiedemann, Urs AchimThu, 17 Jan 2019 03:45:16 GMT2019-01-14arXiv:1901.04503http://cds.cern.ch/record/2654127['arXiv:1901.04503']arXiv:1901.04503Detecting the Stochastic Gravitational Wave Background from Primordial Black Hole Formation
http://cds.cern.ch/record/2652810
Primordial Black Holes (PBH) from peaks in the curvature power spectrum could constitute today an important fraction of the Dark Matter in the Universe. At horizon reentry, during the radiation era, order one fluctuations collapse gravitationally to form black holes and, at the same time, generate a stochastic background of gravitational waves coming from second order anisotropic stresses in matter. We study the amplitude and shape of this background for several phenomenological models of the curvature power spectrum that can be embedded in waterfall hybrid inflation, axion, domain wall, and boosts of PBH formation at the QCD transition. For a broad peak or a nearly scale invariant spectrum, this stochastic background is generically enhanced by about one order of magnitude, compared to a sharp feature. As a result, stellar-mass PBH from Gaussian fluctuations with a wide mass distribution are already in strong tension with the limits from Pulsar Timing Arrays, if they constitute a non negligible fraction of the Dark Matter. But this result is mitigated by the uncertainties on the curvature threshold leading to PBH formation. LISA will have the sensitivity to detect or rule out light PBH down to $10^{-14} M_{\odot}$. Upcoming runs of LIGO/Virgo and future interferometers such as the Einstein Telescope will increase the frequency lever arm to constrain PBH from the QCD transition. Ultimately, the future SKA Pulsar Timing Arrays could probe the existence of even a single stellar-mass PBH in our Observable Universe.Clesse, SebastienGarcía-Bellido, JuanOrani, StefanoWed, 02 Jan 2019 03:36:38 GMT2018-12-28arXiv:1812.11011http://cds.cern.ch/record/2652810['arXiv:1812.11011']arXiv:1812.11011Model-independent Bounds on the Standard Model Effective Theory from Flavour Physics
http://cds.cern.ch/record/2652802
Meson-antimeson mixing provides the most stringent constraints on baryon- and lepton-number conserving New Physics, probing scales higher than $10^5$ TeV. In the context of the effective theory of weak interactions, these constraints translate into severe bounds on the coefficients of $\Delta F=2$ operators. Generalizing to the effective theory invariant under the Standard Model gauge group, valid above the electroweak scale, the bounds from $\Delta F=2$ processes also affect $\Delta F=1$ and even $\Delta F=0$ operators, due to log-enhanced radiative corrections induced by Yukawa couplings. We systematically analyze the effect of the renormalization group evolution above the electroweak scale and provide for the first time the full set of constraints on all relevant dimension-six operators.Silvestrini, LucaValli, MauroTue, 01 Jan 2019 03:26:36 GMT2018-12-28arXiv:1812.10913http://cds.cern.ch/record/2652802['arXiv:1812.10913']arXiv:1812.10913Transverse momentum dependence in double parton scattering
http://cds.cern.ch/record/2652740
In this review, we describe the status of transverse momentum dependence (TMD) in double parton scattering (DPS). The different regions of TMD DPS are discussed, and expressions given for the DPS cross section contributions that make use of as much perturbative information as possible. The regions are then combined with each other as well as with single parton scattering to obtain a complete expression for the cross section. Particular emphasis is put on the differences and similarities to transverse momentum dependence in single parton scattering. We further discuss the status of the factorisation proof for double colour singlet production in DPS, which is now on a similar footing to the proofs for TMD factorisation in single Drell-Yan, discuss parton correlations and give an outlook on possible research on DPS in the near future.Gaunt, Jonathan R.Kasemets, TomasThu, 27 Dec 2018 03:46:46 GMT2018-12-21arXiv:1812.09099http://cds.cern.ch/record/2652740['arXiv:1812.09099']arXiv:1812.09099Supersymmetry, direct and indirect constraints
http://cds.cern.ch/record/2652656
We present an overview of direct and indirect constraints in the MSSM, in CP-conserving and CP-violating MSSM scenarios, with some emphasis on the importance of combining the constraints from different sectors, namely SUSY and Higgs direct searches at the LHC, flavour physics, dark matter and electric dipole moments.Mahmoudi, F.Sat, 22 Dec 2018 04:01:24 GMT2018-12-20arXiv:1812.08783http://cds.cern.ch/record/2652656['arXiv:1812.08783']arXiv:1812.08783Nonperturbative Matching Between Equal-Time and Lightcone Quantization
http://cds.cern.ch/record/2652655
We investigate the nonperturbative relation between lightcone (LC) and standard equal-time (ET) quantization in the context of $\lambda \phi^4$ theory in $d=2$. We discuss the perturbative matching between bare parameters and the failure of its naive nonperturbative extension. We argue that they are nevertheless the same theory nonperturbatively, and that furthermore the nonperturbative map between bare parameters can be extracted from ET perturbation theory via Borel resummation of the mass gap. We test this map by using it to compare physical quantities computed using numerical Hamiltonian truncation methods in ET and LC.Fitzpatrick, A. LiamKatz, EmanuelWalters, Matthew T.Sat, 22 Dec 2018 04:01:16 GMT2018-12-19arXiv:1812.08177http://cds.cern.ch/record/2652655['arXiv:1812.08177']arXiv:1812.08177Symmetry Breaking and Reheating after Inflation in No-Scale Flipped SU(5)
http://cds.cern.ch/record/2652654
No-scale supergravity and the flipped SU(5)$\times$U(1) gauge group provide an ambitious prototype string-inspired scenario for physics below the string scale, which can accommodate the Starobinsky-like inflation favoured by observation when the inflaton is associated with one of the singlet fields associated with neutrino mass generation. During inflation, the vacuum remains in the unbroken GUT phase, and GUT symmetry breaking occurs later when a field with a flat direction (the flaton) acquires a vacuum expectation value. Inflaton decay and the reheating process depend crucially on GUT symmetry breaking, as decay channels open and close, depending on the value of the flaton vacuum expectation value. Here, we consider the simultaneous cosmological evolution of both the inflaton and flaton fields after inflation. We distinguish weak, moderate and strong reheating regimes, and calculate in each case the entropy produced as all fields settle to their global minima. These three reheating scenarios differ in the value of a Yukawa coupling that introduces mass mixing between the singlets and the ${\bf 10}$s of SU(5). The dynamics of the GUT transition has an important impact on the production of gravitinos, and we also discuss the pattern of neutrino masses we expect in each of the three cases. Finally, we use recent CMB limits on neutrino masses to constrain the reheating models, finding that neutrino masses and the cosmological baryon asymmetry can both be explained if the reheating is strong.Ellis, JohnGarcia, Marcos A.G.Nagata, NatsumiNanopoulos, Dimitri V.Olive, Keith A.Sat, 22 Dec 2018 04:01:08 GMT2018-12-19arXiv:1812.08184http://cds.cern.ch/record/2652654['arXiv:1812.08184']arXiv:1812.08184The CKM parameters in the SMEFT
http://cds.cern.ch/record/2652545
Extraction of the Cabibbo-Kobayashi-Maskawa (CKM) matrix from flavour observables can be affected by physics beyond the Standard Model (SM). We provide a general roadmap to take this into account, which we apply to the case of the Standard Model Effective Field Theory (SMEFT). We choose a set of four input observables that determine the four Wolfenstein parameters, and discuss how the effects of dimension-six operators can be included in their definition. We provide numerical values and confidence intervals for the CKM parameters, and compare them with the results of CKM fits obtained in the SM context. Our approach allows one to perform general SMEFT analyses in a consistent fashion, independently of any assumptions about the way new physics affects flavour observables. We discuss a few examples illustrating how our approach can be implemented in practice.Descotes-Genon, SébastienFalkowski, AdamFedele, MarcoGonzález-Alonso, MartínVirto, JavierFri, 21 Dec 2018 04:02:20 GMT2018-12-19arXiv:1812.08163http://cds.cern.ch/record/2652545['arXiv:1812.08163']arXiv:1812.08163New global fits to $b \to s$ data with all relevant parameters
http://cds.cern.ch/record/2652543
The LHCb experiment has made several measurements in $b \to s$ transitions which indicate tensions with the Standard Model predictions. Assuming the source of these tensions to be new physics, we present new global fits to all Wilson coefficients which can effectively receive beyond the Standard Model contributions. While the theoretically clean ratios $R_{K^{(*)}}$ which are sensitive to lepton flavour non-universality may unambiguously establish lepton non-universal new physics in the near future, most of the other tensions with the SM in the $b \to s$ data, in particular in the angular observables of the $B\to K^* \mu\mu$ decay and in the branching ratio of the $B_s \to \phi \mu\mu$ decay, depend on the estimates of non-factorisable power corrections. Therefore, we also analyse the dependence of the new global fit on these corrections.Hurth, TobiasArbey, AlexandreMahmoudi, FarvahNeshatpour, SiavashFri, 21 Dec 2018 04:02:18 GMT2018-12-18arXiv:1812.07602http://cds.cern.ch/record/2652543['arXiv:1812.07602']arXiv:1812.07602Skewed Sudakov Regime, Harmonic Numbers, and Multiple Polylogarithms
http://cds.cern.ch/record/2652377
On the example of massless QED we study an asymptotic of the vertex when only one of the two virtualities of the external fermions is sent to zero. We call this regime the skewed Sudakov regime. First, we show that the asymptotic is described with a single form factor, for which we derive a linear evolution equation. The linear operator involved in this equation has a discrete spectrum. Its eigenfunctions and eigenvalues are found. The spectrum is a shifted sequence of harmonic numbers. With the spectrum found, we represent the expansion of the asymptotic in the fine structure constant in terms of multiple polylogarithms. Using this representation, the exponentiation of the doubly logarithmic corrections of the Sudakov form factor is recovered. It is pointed out that the form factor of the skewed Sudakov regime is growing with the virtuality of a fermion decreasing at a fixed virtuality of another fermion.Kim, Victor T.Matveev, Victor A.Pivovarov, Grigorii B.Thu, 20 Dec 2018 03:24:54 GMT2018-12-18arXiv:1812.07269http://cds.cern.ch/record/2652377['arXiv:1812.07269']arXiv:1812.07269Jet production in charged-current deep-inelastic scattering to third order in QCD
http://cds.cern.ch/record/2652279
The production of jets in charged-current deep-inelastic scattering (CC DIS) probes simultaneously the strong and the electroweak sectors of the Standard Model; its measurement provides important information on the quark flavour structure of the proton. We compute third-order (N3LO) perturbative QCD corrections to this process, fully differential in the jet and lepton kinematics. We observe a substantial reduction in the theory uncertainty, to sub-percent level throughout the relevant kinematical range, thus enabling precision phenomenology with jet observables.Gehrmann, T.Niehues, J.Huss, A.Vogt, A.Walker, D.M.Wed, 19 Dec 2018 04:15:54 GMT2018-12-14arXiv:1812.06104http://cds.cern.ch/record/2652279['arXiv:1812.06104']arXiv:1812.06104Polarized backgrounds of relic gravitons
http://cds.cern.ch/record/2652185
The polarizations of the tensor modes of the geometry evolving in cosmological backgrounds are treated as the components of a bispinor whose dynamics follows from an appropriate gauge-invariant action. This novel framework bears a close analogy with the (optical) Jones calculus and leads to a compact classification of the various interactions able to polarize the relic gravitons.Giovannini, MassimoTue, 18 Dec 2018 03:03:07 GMT2018-12-13CERN-TH-2018-215http://cds.cern.ch/record/26521852018215Collectivity in pp from resummed interference effects?
http://cds.cern.ch/record/2651074
Azimuthal asymmetries $v_n$ in the soft transverse momentum spectra of hadronic collisions can result as a consequence of quantum interference and color flow which translates spatial anisotropies into momentum anisotropies via multipole radiation patterns. Here, we analyze to what extent these effects result in signal strengths $v_n\lbrace 2s\rbrace$ that can persist in higher order $(2s)$ cumulants. In a simple model of soft multi-particle production with quantum interference effects in which $m$ particles are emitted from $N$ sources and in which interference contributions appear naturally ordered in inverse powers of the adjoint color trace, $1/(N_c^2-1)$, we provide the first resummed calculation of all powers of $m^2/(N_c^2-1)$. This allows one to determine all higher order flow cumulants $v_n\lbrace 2s\rbrace$ with the same parametric accuracy. For a phenomenologically relevant range of $N$ sources emitting $m$ particles, we find that the even flow coefficients $v_n\lbrace 2s\rbrace$ decrease very mildly with increasing cumulants. This provides a proof of principle that non-vanishing higher order cumulants $v_n\lbrace 2s\rbrace$ can persist in systems that exhibit neither final state interactions nor phenomena related to high (saturated) initial parton densities.Blok, BorisWiedemann, Urs AchimThu, 13 Dec 2018 03:57:15 GMT2018-12-10arXiv:1812.04113http://cds.cern.ch/record/2651074['arXiv:1812.04113']arXiv:1812.04113