scholarly journals Simulating hard photon production with Whizard

2020 ◽  
Vol 80 (7) ◽  
Author(s):  
J. Kalinowski ◽  
W. Kotlarski ◽  
P. Sopicki ◽  
A. F. Żarnecki
Keyword(s):  
Dark Matter ◽  
Pair Production ◽  
Cross Sections ◽  
New Physics ◽  
Hard Photon ◽  
Initial State ◽  
Flexible Tool ◽  
Bhabha Scattering ◽  
State Radiation ◽  
Neutrino Pair

Abstract One of the important goals of the proposed future $$\hbox {e}^{+}\hbox {e}^{-}$$e+e- collider experiments is the search for dark matter particles using different experimental approaches. The most general search approach is based on the mono-photon signature, which is expected when production of the invisible final state is accompanied by a hard photon from initial state radiation. Analysis of the energy spectrum and angular distributions of those photons can shed light on the nature of dark matter and its interactions. Therefore, it is crucial to be able to simulate the signal and background samples in a uniform framework, to avoid possible systematic biases. The Whizard program is a flexible tool, which is widely used by $$\hbox {e}^{+}\hbox {e}^{-}$$e+e- collaborations for simulation of many different “new physics” scenarios. We propose the procedure of merging the matrix element calculations with the lepton ISR structure function implemented in Whizard. It allows us to reliably simulate the mono-photon events, including the two main Standard Model background processes: radiative neutrino pair production and radiative Bhabha scattering. We demonstrate that cross sections and kinematic distributions of mono-photon in neutrino pair-production events agree with corresponding predictions of the $$\mathcal{KK}$$KK MC, a Monte Carlo generator providing perturbative predictions for SM and QED processes, which has been widely used in the analysis of LEP data.

scholarly journals Spin-one dark matter and gamma ray signals from the galactic center

2020 ◽  
Vol 2020 (8) ◽  
Author(s):  
H. Hernández-Arellano ◽  
M. Napsuciale ◽  
S. Rodríguez
Keyword(s):  
Dark Matter ◽  
Cross Section ◽  
Gamma Ray ◽  
Galactic Center ◽  
Photon Emission ◽  
Scalar Coupling ◽  
Initial State ◽  
Internal Bremsstrahlung ◽  
Resonance Effects ◽  
State Radiation

Abstract In this work we study the possibility that the gamma ray excess (GRE) at the Milky Way galactic center come from the annihilation of dark matter with a (1, 0) ⊕ (0, 1) space-time structure (spin-one dark matter, SODM). We calculate the production of prompt photons from initial state radiation, internal bremsstrahlung, final state radiation including the emission from the decay products of the μ, τ or hadronization of quarks. Next we study the delayed photon emission from the inverse Compton scattering (ICS) of electrons (produced directly or in the prompt decay of μ, τ leptons or in the hadronization of quarks produced in the annihilation of SODM) with the cosmic microwave background or starlight. All these mechanisms yield significant contributions only for Higgs resonant exchange, i.e. for M ≈ MH /2, and the results depend on the Higgs scalar coupling to SODM, gs. The dominant mechanism at the GRE bump is the prompt photon production in the hadronization of b quarks produced in $$ \overline{D}D\to \overline{b}b $$ D ¯ D → b ¯ b , whereas the delayed photon emission from the ICS of electrons coming from the hadronization of b quarks produced in the same reaction dominates at low energies (ω < 0.3 GeV ) and prompt photons from c and τ , as well as from internal bremsstrahlung, yield competitive contributions at the end point of the spectrum (ω ≥ 30 GeV ). Taking into account all these contributions, our results for photons produced in the annihilation of SODM are in good agreement with the GRE data for gs ∈ [0.98, 1.01] × 10−3 and M ∈ [62.470, 62.505] GeV . We study the consistency of the corresponding results for the dark matter relic density, the spin-independent dark matter-nucleon cross-section σp and the cross section for the annihilation of dark matter into $$ \overline{b}b $$ b ¯ b , τ+τ−, μ+μ− and γγ, taking into account the Higgs resonance effects, finding consistent results in all cases.

scholarly journals Signs of new physics in top quark pair production associated with a neutrino pair at the LHC

2020 ◽  
Vol 101 (9) ◽  
Author(s):  
Daruosh Haji Raissi ◽  
Javad Ebadi ◽  
Mojtaba Mohammadi Najafabadi
Keyword(s):  
Pair Production ◽  
Top Quark ◽  
New Physics ◽  
Neutrino Pair

scholarly journals Open charm studies at Belle

2019 ◽  
Vol 212 ◽  
pp. 09003
Author(s):  
Valentina Zhukova
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Open Charm ◽  
Mass Energy ◽  
Initial State ◽  
Belle Detector ◽  
Section Measurement ◽  
Angular Analysis ◽  
State Radiation ◽  
Radiation Technique

We present the new results of measurements of the exlusive cross sections of the e+ e− annihilation to charmed meson pairs as a function of √ ceneter-of-mass energy from the open charm threashold up to $ \sqrt s = {\rm{6 GeV}} $ using initial state radiation technique. The analysis is based on a data sample collected by the Belle detector with an integrated luminosity of 951 fb−1. The accuracy of the cross section measurement is increased by a factor of 2 in comparison with the first Belle study. We have performed the first angular analysis + −→ D*± D*∓ of the $ {e^{\rm{ + }}}{e^ - } \to {D^{* \pm }}{D^{* \mp }} $ process and decomposed this exclusive cross section into three components corresponding to the different D* helicities.

scholarly journals Sensitivity of future linear $$\hbox {e}^+\hbox {e}^-$$ colliders to processes of dark matter production with light mediator exchange

2021 ◽  
Vol 81 (10) ◽  
Author(s):  
Jan Kalinowski ◽  
Wojciech Kotlarski ◽  
Krzysztof Mȩkała ◽  
Paweł Sopicki ◽  
Aleksander Filip Żarnecki
Keyword(s):  
Dark Matter ◽  
Linear Collider ◽  
Production Cross ◽  
Photon Emission ◽  
International Linear Collider ◽  
High Energy ◽  
Initial State ◽  
Final State ◽  
State Radiation ◽  
Wide Range

AbstractAs any $$e^+e^-$$ e + e - scattering process can be accompanied by a hard photon emission from the initial state radiation, the analysis of the energy spectrum and angular distributions of those photons can be used to search for hard processes with an invisible final state. Thus high energy $$e^+e^-$$ e + e - colliders offer a unique possibility for the most general search of dark matter (DM) based on the mono-photon signature. We consider production of DM particles at the International Linear Collider (ILC) and Compact Linear Collider (CLIC) experiments via a light mediator exchange. Detector effects are taken into account within the Delphes fast simulation framework. Limits on the light DM production in a simplified model are set as a function of the mediator mass and width based on the expected two-dimensional distributions of the reconstructed mono-photon events. The experimental sensitivity is extracted in terms of the DM production cross section. Limits on the mediator couplings are then presented for a wide range of mediator masses and widths. For light mediators, for masses up to the centre-of-mass energy of the collider, coupling limits derived from the mono-photon analysis are more stringent than those expected from direct resonance searches in decay channels to SM particles.

scholarly journals Event Generators for Multi Hadronic Production in e+e− Collisions

2019 ◽  
Vol 218 ◽  
pp. 07005
Author(s):  
Rong-Gang Ping ◽  
Zhen Gao
Keyword(s):  
Cross Sections ◽  
Radiation Effects ◽  
Event Generator ◽  
Initial State ◽  
Order Accuracy ◽  
State Radiation ◽  
Hadronic Production ◽  
Event Generation ◽  
Exclusive Processes ◽  
Area Law

An event generator for multi hadron production is presented for measuring the R value in the τ-charm energy region with e+e− collisions. The initial state radiation effects are considered up to second order accuracy, and the radiative correction factor is calculated with hadronic Born cross sections. The established exclusive processes are generated according to their measured cross sections, while the missing processes are generated using the LUND Area Law model, and its parameters are tuned with data collected at $ \sqrt s $ = 3.08 GeV. The optimized values are validated with data in the range $ \sqrt s $= 2.2324 ∼ 3.671 GeV. These optimized parameters are universally valid for event generation below the DD¯threshold.

scholarly journals e+e−→K+K−π+π−,K+K−π0π0andK+K−K+K−cross sections measured with initial-state radiation

2007 ◽  
Vol 76 (1) ◽  
Author(s):  
B. Aubert ◽  
M. Bona ◽  
D. Boutigny ◽  
Y. Karyotakis ◽  
J. P. Lees ◽  
...  
Keyword(s):  
Cross Sections ◽  
Initial State Radiation ◽  
Initial State ◽  
State Radiation

scholarly journals MEASUREMENT AND INTERPRETATION OF LEPTON-PAIR PRODUCTION AT LEP2 ENERGIES

2001 ◽  
Vol 16 (supp01a) ◽  
pp. 336-338
Author(s):  
ANETTE BEHRMANN
Keyword(s):  
Pair Production ◽  
Cross Sections ◽  
Preliminary Analysis ◽  
Center Of Mass ◽  
New Physics ◽  
Lepton Pair ◽  
Lepton Pair Production ◽  
Delphi Detector ◽  
The Standard Model ◽  
Model Predictions

A preliminary analysis of the lepton-pair production in e+e- annihilations at LEP2 center-of-mass energies using the data collected between 130 GeV and LEP2 highest energies (i.e. exceeding 205 GeV) with the DELPHI detector is presented. The values obtained for the cross-sections and forword-backward asymmetries are used to test the Standard Model predictions and to derive limits for possible new physics phenomena beyond it.

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