The strong coupling constant
α
s
is determined from inclusive jet and dijet cross sections in neutral-current deep-inelastic
ep
scattering (DIS) measured at HERA by the H1 collaboration using ...next-to-next-to-leading order (NNLO) QCD predictions. The dependence of the NNLO predictions and of the resulting value of
α
s
(
m
Z
)
at the
Z
-boson mass
m
Z
are studied as a function of the choice of the renormalisation and factorisation scales. Using inclusive jet and dijet data together, the strong coupling constant is determined to be
α
s
(
m
Z
)
=
0.1157
(
20
)
exp
(
29
)
th
. Complementary,
α
s
(
m
Z
)
is determined together with parton distribution functions of the proton (PDFs) from jet and inclusive DIS data measured by the H1 experiment. The value
α
s
(
m
Z
)
=
0.1142
(
28
)
tot
obtained is consistent with the determination from jet data alone. The impact of the jet data on the PDFs is studied. The running of the strong coupling is tested at different values of the renormalisation scale and the results are found to be in agreement with expectations.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A detailed investigation of hadronic interactions is performed using π−-mesons with energies in the range 2–10 GeV incident on a high granularity silicon–tungsten electromagnetic calorimeter. The ...data were recorded at FNAL in 2008. The region in which the π−-mesons interact with the detector material and the produced secondary particles are characterised using a novel track-finding algorithm that reconstructs tracks within hadronic showers in a calorimeter in the absence of a magnetic field. The principle of carrying out detector monitoring and calibration using secondary tracks is also demonstrated.
We present a study of the response of the highly granular Digital Hadronic Calorimeter with steel absorbers, the Fe-DHCAL, to positrons, muons, and pions with momenta ranging from 2 to 60GeV/c. ...Developed in the context of the CALICE collaboration, this hadron calorimeter utilises Resistive Plate Chambers as active media, interspersed with steel absorber plates. With a transverse granularity of 1×1cm2 and a longitudinal segmentation of 38 layers, the calorimeter counted 350,208 readout channels, each read out with single-bit resolution (digital readout). The data were recorded in the Fermilab test beam in 2010–11. The analysis includes measurements of the calorimeter response and the energy resolution to positrons and muons, as well as detailed studies of various shower shape quantities. The results are compared to simulations based on Geant4, which utilise different electromagnetic and hadronic physics lists.
The gain of silicon photomultipliers (SiPMs) increases with bias voltage and decreases with temperature. To operate SiPMs at stable gain, the bias voltage can be readjusted to compensate for ...temperature changes. We have tested this concept with 30 SiPMs from three manufacturers (Hamamatsu, KETEK and CPTA) operating in a climate chamber at CERN by varying temperatures between 1ˆC and 48ˆC. We built an adaptive power supply that uses a linear dependence of the bias voltage on temperature. We stabilized four SiPMs simultaneously with only one compensation parameter for the readjustment of the bias voltage of four SiPMs. For all tested Hamamatsu and CPTA SiPMs we achieved our goal of limiting gain changes to less than ±0.5% in the 20–30ˆC temperature range.
Abstract
The CALICE collaboration is developing highly granular
electromagnetic and hadronic calorimeters for detectors at future
energy frontier electron-positron colliders. After successful tests
...of a physics prototype, a technological prototype of the Analog
Hadron Calorimeter has been built, based on a design and
construction techniques scalable to a collider detector. The
prototype consists of a steel absorber structure and active layers
of small scintillator tiles that are individually read out by
directly coupled SiPMs. Each layer has an active area of
72 × 72 cm^2 and a tile size of
3 × 3 cm^2. With 38 active layers, the prototype
has nearly 22,000 readout channels, and its total thickness
amounts to 4.4 nuclear interaction lengths. The dedicated readout
electronics provide time stamping of each hit with an expected
resolution of about 1 ns. The prototype was constructed in
2017 and commissioned in beam tests at DESY. It recorded muons,
hadron showers and electron showers at different energies in test
beams at CERN in 2018. In this paper, the design of the prototype,
its construction and commissioning are described. The methods used
to calibrate the detector are detailed, and the performance achieved
in terms of uniformity and stability is presented.
A highly granular electromagnetic calorimeter with scintillator strip readout is being developed for future linear collider experiments. A prototype of 21.5 X0 depth and 180×180mm2 transverse ...dimensions was constructed, consisting of 2160 individually read out 10×45×3mm3 scintillator strips. This prototype was tested using electrons of 2–32 GeV at the Fermilab Test Beam Facility in 2009. Deviations from linear energy response were less than 1.1%, and the intrinsic energy resolution was determined to be (12.5±0.1(stat.)±0.4(syst.))%∕EGeV⊕(1.2±0.1(stat.)−0.7+0.6(syst.))%, where the uncertainties correspond to statistical and systematic sources, respectively.
This paper presents results obtained with the combined CALICE Scintillator Electromagnetic Calorimeter, Analogue Hadronic Calorimeter and Tail Catcher & Muon Tracker, three high granularity ...scintillator-silicon photomultiplier calorimeter prototypes. The response of the system to pions with momenta between 4 GeV/c and 32 GeV/c is analysed, including the average energy response, resolution, and longitudinal shower profiles. Two techniques are applied to reconstruct the initial particle energy from the measured energy depositions; a standard energy reconstruction which is linear in the measured depositions and a software compensation technique based on reweighting individually measured depositions according to their hit energy. The results are compared to predictions of the GEANT 4 physics lists QGSP_BERT_HP and FTFP_BERT_HP.
The CALICE Semi-Digital Hadronic CALorimeter (SDHCAL) prototype using Glass Resistive Plate Chambers as a sensitive medium is the first technological prototype of a family of high-granularity ...calorimeters developed by the CALICE collaboration to equip the experiments of future leptonic colliders. It was exposed to beams of hadrons, electrons and muons several times in the CERN PS and SPS beamlines between 2012 and 2018. We present here a new method of particle identification within the SDHCAL using the Boosted Decision Trees (BDT) method applied to the data collected in 2015. The performance of the method is tested first with Geant4-based simulated events and then on the data collected by the SDHCAL in the energy range between 10 and 80 GeV with 10 GeV energy steps. The BDT method is then used to reject the electrons and muons that contaminate the SPS hadron beams. The rejection power of the new method is estimated to be as high as 99.0% for the muons and 99.4% for the electrons associated to a pion selection efficiency of about 95.0%.
The latest developments of calorimeters using scintillators as active medium for detectors at the ILC are reviewed. We mention those having already a prototype that was tested in the beam. Besides ...classical scintillator tile calorimeters with smallest tiles ever used, a completely new approach was proposed with independent measurement of scintillation and Cherenkov light produced in fibers. Special attention is given to new photodetectors - silicon photomultipliers - which have been extensively used for the scintillator readout. Their main advantages are a high gain ~10 6 at a low bias voltage 55-75 V, easy integration into a scintillator and a reasonable price.
The high granularity of the CALICE Semi-Digital Hadronic CALorimeter (SDHCAL) provides the capability to reveal the track segments present in hadronic showers. These segments are then used as a tool ...to probe the behaviour of the active layers in situ, to better reconstruct the energy of these hadronic showers and also to distinguish them from electromagnetic ones. In addition, the comparison of these track segments in data and the simulation helps to discriminate among the different shower models used in the simulation. To extract the track segments in the showers recorded in the SDHCAL, a Hough Transform is used after being adapted to the presence of the dense core of the hadronic showers and the SDHCAL active medium structure.
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