arXiv subjects

S. P. Denisov

Publications and source records attributed to S. P. Denisov.

12 recordsLinked to original sources

arXiv2022

Mu2e-II: Muon to electron conversion with PIP-II

An observation of Charged Lepton Flavor Violation (CLFV) would be unambiguous evidence for physics beyond the Standard Model. The Mu2e and COMET experiments, under construction, are designed to push the sensitivity to CLFV in the mu to e conversion process to unprecedented levels. Whether conversion is observed or not, there is a strong case to be made for further improving sensitivity, or for examining the process on additional target materials. Mu2e-II is a proposed upgrade to Mu2e, with at least an additional order of magnitude in sensitivity to the conversion rate over Mu2e. The approach and challenges for this proposal are summarized. Mu2e-II may be regarded as the next logical step in a continued high-intensity muon program at FNAL.

hep-ex↗

arXiv2019

Properties of a simple e/gamma detector consisting of a lead convertor and a hodoscope

The results of the calculations of coordinate resolution and hadron rejection factor for a simple e/gamma detector consisting of a lead convertor followed by a hodoscope are presented. For the simulation of showers, initiated in the converter by electrons and hadrons with energies upto 1 TeV GEANT4 is used. It is shown that the best coordinate resolution for electrons is achieved when the converter thickness is closed to the shower maximum. For example, at 200 GeV with 2 mm strip width hodoscope it is equal to sigma=89 microns provided a "truncated mean" coordinate estimation is used. The optimal thickness of the converter for hadron rejection is also close to tmax. For 200 GeV beam of electrons and protons the rejection factor of 10^-4 for 0.9 electron detection efficiency can be reached using only data on charged particles multiplicities. Information on the spatial distribution of the shower particles after the converter allows to enhance further the rejection by several times.

physics.ins-det↗

arXiv2019

Distributions of the charged particles multiplicities in the electromagnetic showers initiated by 10 to 1000 GeV electrons in lead

Distributions of the charged particles multiplicities in the electromagnetic showers initiated by 10 to 1000 GeV electrons in lead are calculated using GEANT4. It is shown that they are well fitted by the inverse sum of two exponents. The evolution of the multiplicity distribution shapes as a function of the lead depth is discussed. An estimate of the energy resolution of a simple e,γ detector consisting of a high Z convertor and a counter of the shower electrons and positrons is presented.

physics.ins-det↗

arXiv2018

Energy, radial and time distributions of the charged particles at the maximum of electromagnetic showers initiated by 5-1000 GeV electrons in Fe, W and Pb

The results of calculations of the charged particles energy, radial and time distributions at the maximum of electromagnetic showers initiated by electrons with energies from 5 to 1000 GeV in Fe, W and Pb are presented. It is shown that the shapes of energy distributions weekly depend on the electron energy, radial distributions for different materials become close to each other if radius is expressed in g/cm2 and the time spread of the shower particles is in the picosecond range. Analysis of the data obtained allows us to conclude that a high Z material placed in a high energy electron beam can be used as a source of short and intense bunches of ultarelativistic positrons and electrons with subpicosecond time spread.

physics.ins-det↗

arXiv2018

Multiplicity distributions of the charged particles at the maximum of electromagnetic showers initiated by 5-1000 GeV electrons in Fe, W and Pb

Charged particles multiplicity distributions at the maximum of electromagnetic showers initiated by 5 to 1000 GeV electrons in Fe, W, and Pb were calculated using GEANT4. It is shown that they are reasonably well fitted by the inverse sum of two exponents and the energy dependence of the average multiplicity follows power law with the power of ~0.95 for all studied materials.

physics.ins-det↗

arXiv2012

Measurement of the differential cross section dσ/dt in elastic $p\bar{p}$ scattering at sqrt(s)=1.96 TeV

We present a measurement of the elastic differential cross section $dσ(p\bar{p}\rightarrow p\bar{p})/dt$ as a function of the four-momentum-transfer squared t. The data sample corresponds to an integrated luminosity of $\approx 31 nb^{-1}$ collected with the D0 detector using dedicated Tevatron $p\bar{p} $ Collider operating conditions at sqrt(s) = 1.96 TeV and covers the range $0.26 <|t|< 1.2 GeV^2$. For $|t|<0.6 GeV^2$, dσ/dt is described by an exponential function of the form $Ae^{-b|t|}$ with a slope parameter $ b = 16.86 \pm 0.10(stat) \pm 0.20(syst) GeV^{-2}$. A change in slope is observed at $|t| \approx 0.6 GeV^2$, followed by a more gradual |t| dependence with increasing values of |t|.

hep-ex↗

arXiv2012

Search for pair production of the scalar top quark in muon+tau final states

We present a search for the pair production of scalar top quarks ($\tilde{t}_{1}$), the lightest supersymmetric partners of the top quarks, in $p\bar{p}$ collisions at a center-of-mass energy of 1.96 TeV, using data corresponding to an integrated luminosity of {7.3 $fb^{-1}$} collected with the \dzero experiment at the Fermilab Tevatron Collider. Each scalar top quark is assumed to decay into a $b$ quark, a charged lepton, and a scalar neutrino ($\tildeν$). We investigate final states arising from $\tilde{t}_{1} \bar{\tilde{t}_{1}} \rightarrow b\bar{b}μτ\tildeν \tildeν$ and $\tilde{t}_{1} \bar{\tilde{t}_{1}} \rightarrow b\bar{b}ττ\tildeν \tildeν$. With no significant excess of events observed above the background expected from the standard model, we set exclusion limits on this production process in the ($m_{\tilde{t}_{1}}$,$m_{\tildeν}$) plane.

hep-ex↗

arXiv2010

Relative luminosity measurement of the LHC with the ATLAS forward calorimeter

In this paper it is shown that a measurement of the relative luminosity changes at the LHC may be obtained by analysing the currents drawn from the high voltage power supplies of the electromagnetic section of the forward calorimeter of the ATLAS detector. The method was verified with a reproduction of a small section of the ATLAS forward calorimeter using proton beams of known beam energies and variable intensities at the U-70 accelerator at IHEP in Protvino, Russia. The experimental setup and the data taking during a test beam run in April 2008 are described in detail. A comparison of the measured high voltage currents with reference measurements from beam intensity monitors shows a linear dependence on the beam intensity. The non-linearities are measured to be less than 0.5 % combining statistical and systematic uncertainties.

physics.ins-det↗

arXiv2005

Measurements of the Dalitz Plot Parameters for $K^{\pm}\toπ^{\pm}π^0π^0$ Decays

The $g$, $h$, and $k$ Dalitz plot parameters, which are coefficients in a series expansion of the squared module of the matrix element $|M(u,v)|^{2} \propto 1 + gu + hu^{2} + kv^{2}$ ($u$, $v$ are invariant variables), have been measured for $K^{\pm}\to π^{\pm} π^{0} π^{0}$ decays using $35 GeV/c$ hadron beams at the IHEP (Protvino) accelerator. Dependences of parameters and fit quality on the $π^0π^0$ mass cut were investigated. The results point to the important role of $π^+π^- \to π^0π^0$ charge exchange scattering near the $π^0π^0$ mass threshold. The comparison of our data with previous measurements is presented.

hep-ex↗

arXiv2005

A search for J^{PC}=1^{-+} exotic mesons in the pi- pi- pi+ and pi- pi0 pi0 systems

A partial wave analysis (PWA) of the pi-pi-pi+ and pi-pi0pi0 systems produced in the reaction pi- p -> (3pi)-p at 18 GeV/c was carried out using an isobar model assumption. This analysis is based on 3.0M pi-pi0pi0 events and 2.6M pi-pi-pi+ events and shows production of the a2(1320), pi2(1670) and π(1800) mesons. An earlier analysis of 250K pi-pi-pi+ events from the same experiment showed possible evidence for a J^{PC}=1^{-+}$ exotic meson with a mass of 1.6 GeV/c^2 decaying into rho pi. In this analysis of a higher statistics sample of the (3pi)- system in two charged modes we find no evidence of an exotic meson.

hep-ex↗

arXiv2004

Measurements of the Charge Asymmetry of the Dalitz Plot Parameters for $K^{\pm}\toπ^{\pm}π^0π^0$ Decays

The charge asymmetry of the g, h, and k Dalitz plot parameters for $K^{\pm}\toπ^{\pm}π^0π^0$ decays has been measured with 35 GeV/c hadron beams at the 70 GeV IHEP accelerator. The g, h and k values obtained appear to be identical for $K^{\pm}\toπ^{\pm}π^0π^0$ decays within the errors quoted. In particular, the charge asymmetry $A_g = (g^+ - g^-)/(g^+ + g^-)$ of the slope g is equal to $(0.2 \pm 1.9)\cdot 10^{-3}$.

hep-ex↗

arXiv2003

A Study of the ηπ^{0} Spectrum and Search for a J^{PC} = 1^{-+} Exotic Meson

A partial wave analysis (PWA) of the of the $ηπ^0$ system (where $η\to γγ$) produced in the charge exchange reaction $π^-p\to ηπ^0n$ at an incident momentum of 18 GeV$/c$ is presented as a function of ${ηπ^0}$ invariant mass, $m_{ηπ^0}$, and momentum transfer squared, $t_{π^{-}\toηπ}$, from the incident $π^-$ to the outgoing ${ηπ^0}$ system. $S$, $P$ and $D$ waves were included in the PWA. The $a_0(980)$ and $a_2(1320)$ states are clearly observed in the overall ${ηπ^0}$ effective mass distribution as well as in the amplitudes associated with $S$ wave and $D$ waves respectively after partial wave decomposition. The observed distributions in moments (averages of spherical harmonics) were compared to the results from the PWA and the two are consistent. The distribution in $t_{π^{-}\toηπ}$ for individual $D$ waves associated with natural and unnatural parity exchange in the $t$-channel are consistent with Regge phenomenology. Of particular interest in this study is the $P$ wave since this leads to an exotic $J^{PC}=1^{-+}$ for the $ηπ$ system. A $P$ wave is present in the data, however attempts to describe the mass dependence of the amplitude and phase motion with respect to the $D$ wave as a Breit-Wigner resonance are problematic. This has implications regarding the existence of a reported exotic $J^{PC} = 1^{-+}$ meson decaying into $ηπ^0$ with a mass near 1.4 GeV$/c^2$.

hep-ex↗