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Caldeira Balkeståhl, Li
Alternative names
Publications (10 of 56) Show all publications
Anastasi, A., Babusci, D., Berlowski, M., Bloise, C., Bossi, F., Branchini, P., . . . Teubner, T. (2018). Combination of KLOE sigma (e(+) e(-) -> pi(+)pi(-) gamma(gamma)) measurements and determination of a(mu)(pi+pi-) in the energy range 0.10 < s < 0.95 GeV2. Journal of High Energy Physics (JHEP) (3), Article ID 173.
Open this publication in new window or tab >>Combination of KLOE sigma (e(+) e(-) -> pi(+)pi(-) gamma(gamma)) measurements and determination of a(mu)(pi+pi-) in the energy range 0.10 < s < 0.95 GeV2
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2018 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 3, article id 173Article in journal (Refereed) Published
Abstract [en]

The three precision measurements of the cross section sigma (e(+)e(-) -> pi(+)pi(-)gamma(gamma)) using initial state radiation by the KLOE collaboration provide an important input for the prediction of the hadronic contribution to the anomalous magnetic moment of the muon. These measurements are correlated for both statistical and systematic uncertainties and, therefore, the simultaneous use of these measurements requires covariance matrices that fully describe the correlations. We present the construction of these covariance matrices and use them to determine a combined KLOE measurement for sigma (e(+)e(-) -> pi(+)pi(-)gamma(gamma)). We find, from this combination, a two-pion contribution to the muon magnetic anomaly in the energy range 0.10 < s < 0.95 GeV2 of a(mu)(pi+pi-) (489.8 +/- 1.7(stat) +/- 4.8(sys)) x 10(-10).

Place, publisher, year, edition, pages
Springer, 2018
Keywords
e plus -e- Experiments
National Category
Subatomic Physics Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:uu:diva-351704 (URN)10.1007/JHEP03(2018)173 (DOI)000429243600001 ()
Available from: 2018-06-04 Created: 2018-06-04 Last updated: 2018-06-04Bibliographically approved
Anastasi, A., Babusci, D., Bencivenni, G., Berlowski, M., Bloise, C., Bossi, F., . . . Jegerlehner, F. (2017). Measurement of the running of the fine structure constant below 1 GeV with the KLOE detector. Physics Letters B, 767, 485-492
Open this publication in new window or tab >>Measurement of the running of the fine structure constant below 1 GeV with the KLOE detector
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2017 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 767, p. 485-492Article in journal (Refereed) Published
Abstract [en]

We have measured the running of the effective QED coupling constant alpha(s) in the time-like region 0.6 < root s < 0.975 GeV with the KLOE detector at DA Phi NE using the Initial-State Radiation process e(+) e(-) -> mu(+) mu(-)gamma. It represents the first measurement of the running of alpha(s) in this energy region. Our results show a more than 5 sigma significance of the hadronic contribution to the running of alpha(s), which is the strongest direct evidence both in time- and space-like regions achieved in a single measurement. By using the e(+) e(-) -> pi(+) pi(-) cross section measured by KLOE, the real and imaginary parts of the shift Delta alpha(s) have been extracted. From a fit of the real part of Delta alpha(s) and assuming the lepton universality the branching ratio BR(omega -> mu(+) mu(-)) = (6.6 +/- 1.4(stat) +/- 1.7(syst)) (.) 10 (5)has been determined.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2017
Keywords
Vacuum polarization, arunning
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-320023 (URN)10.1016/j.physletb.2016.12.016 (DOI)000397861700074 ()
Funder
EU, FP7, Seventh Framework Programme, FP7-INFRASTRUCTURES2008-1 227431
Note

A KLOE-2 Collaboration

Available from: 2017-04-13 Created: 2017-04-13 Last updated: 2017-11-29Bibliographically approved
Anastasi, A., Babusci, D., Bencivenni, G., Berlowski, M., Bloise, C., Bossi, F., . . . Wolke, M. (2016). Limit on the production of a new vector boson in e+e− → Uγ, U → π+π− with the KLOE experiment. Physics Letters B, 757, 356-361
Open this publication in new window or tab >>Limit on the production of a new vector boson in e+e− → Uγ, U → π+π− with the KLOE experiment
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2016 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 757, p. 356-361Article in journal (Refereed) Published
Abstract [en]

Abstract The recent interest in a light gauge boson in the framework of an extra U(1) symmetry motivates searches in the mass range below 1 GeV. We present a search for such a particle, the dark photon, in e + e − → U γ , U → π + π − based on 28 million e + e − → π + π − γ events collected at DAΦNE by the KLOE experiment. The π + π − production by initial-state radiation compensates for a loss of sensitivity of previous KLOE U → e + e − , μ + μ − searches due to the small branching ratios in the ρ – ω resonance region. We found no evidence for a signal and set a limit at 90% CL on the mixing strength between the photon and the dark photon, ε 2 , in the U mass range between 527 and 987 MeV . Above 700 MeV this new limit is more stringent than previous ones.

Keywords
Dark matter, Dark forces, Dark photon, U boson
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-289366 (URN)10.1016/j.physletb.2016.04.019 (DOI)000376800300048 ()
Funder
EU, European Research Council, RII3-CT-2004-506078EU, FP7, Seventh Framework Programme, 227431 FP7-INFRASTRUCTURES-2008-1
Available from: 2016-04-29 Created: 2016-04-29 Last updated: 2017-11-30Bibliographically approved
Anastasi, A., Caldeira Balkeståh, L., Cao, B., Heijkenskjöld, L., Ikegami Andersson, W., Johansson, T., . . . Wolke, M. (2016). Measurement of the ϕ→π0e+e− transition form factor with the KLOE detector. Physics Letters B, 757, 362-367
Open this publication in new window or tab >>Measurement of the ϕ→π0e+e− transition form factor with the KLOE detector
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2016 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 757, p. 362-367Article in journal (Refereed) Published
Abstract [en]

A measurement of the vector to pseudoscalar conversion decay ϕ→π0e+e− with the KLOE experiment is presented. A sample of ∼9500 signal events was selected from a data set of 1.7 fb−1 of e+e− collisions at s√∼mϕ collected at the DAΦNE e+e− collider. These events were used to obtain the first measurement of the transition form factor |Fϕπ0(q2)| and a new measurement of the branching ratio of the decay: BR(ϕ→π0e+e−)=(1.35±0.05+0.05−0.10)×10−5. The result improves significantly on previous measurements and is in agreement with theoretical predictions.

Keywords
e(+)e(-) collisions; Conversion decay; Transition form factor
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-289057 (URN)10.1016/j.physletb.2016.04.015 (DOI)000376800300049 ()
Funder
EU, European Research Council, RII3-CT-2004-506078EU, FP7, Seventh Framework Programme, FP7-INFRASTRUCTURES-2008-1 227431
Available from: 2016-04-28 Created: 2016-04-28 Last updated: 2017-11-30Bibliographically approved
Anastasi, A., Babusci, D., Bencivenni, G., Berlowski, M., Bloise, C., Bossi, F., . . . Wolke, M. (2016). Precision measurement of the η → π + π − π 0 Dalitz plot distribution with the KLOE detector. Journal of High Energy Physics (JHEP) (5), Article ID 019.
Open this publication in new window or tab >>Precision measurement of the η → π + π − π 0 Dalitz plot distribution with the KLOE detector
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2016 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 5, article id 019Article in journal (Refereed) Published
Abstract [en]

Using 1.6 fb−1 of e + e − → ϕ → ηγ data collected with the KLOE detector at DAΦNE, the Dalitz plot distribution for the η → π + π − π 0 decay is studied with the world’s largest sample of ∼ 4.7 · 106 events. The Dalitz plot density is parametrized as a polynomial expansion up to cubic terms in the normalized dimensionless variables X and Y . The experiment is sensitive to all charge conjugation conserving terms of the expansion, including a gX 2 Y term. The statistical uncertainty of all parameters is improved by a factor two with respect to earlier measurements.

Keywords
e plus -e- Experiments; QCD
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-292944 (URN)10.1007/JHEP05(2016)019 (DOI)000375714100001 ()
Funder
EU, European Research Council, RII3-CT- 2004-506078EU, European Research Council, 227431
Available from: 2016-05-10 Created: 2016-05-10 Last updated: 2017-11-30Bibliographically approved
Tiemens, M., Caldeira Balkeståhl, L., Calén, H., Fransson, K., Johansson, T., Kupsc, A., . . . Zmeskal, J. (2015). A Triggerless readout system for the bar PANDA electromagnetic calorimeter. Paper presented at 16th Int. Conf. on Calorimetry in High Energy Physics (CALOR 2014), Giessen Germany, 6-11 April, 2014. Journal of Physics, Conference Series, 587(1), Article ID 012025.
Open this publication in new window or tab >>A Triggerless readout system for the bar PANDA electromagnetic calorimeter
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2015 (English)In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 587, no 1, article id 012025Article in journal (Refereed) Published
Abstract [en]

One of the physics goals of the future bar PANDA experiment at FAIR is to research newly discovered exotic states. Because the detector response created by these particles is very similar to the background channels, a new type of data readout had to be developed, called 'triggerless' readout. In this concept, each detector subsystem preprocesses the signal, so that in a later stage, high-level phyiscs constraints can be applied to select events of interest. A dedicated clock source using a protocol called SODANET over optical fibers ensures proper synchronisation between the components. For this new type of readout, a new way of simulating the detector response also needed to be developed, taking into account the effects of pile-up caused by the 20 MHz interaction rate.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-287335 (URN)10.1088/1742-6596/587/1/012025 (DOI)
Conference
16th Int. Conf. on Calorimetry in High Energy Physics (CALOR 2014), Giessen Germany, 6-11 April, 2014
Note

PANDA Collaboration, for complete list of authors see http://dx.doi.org/10.1140/epja/i2015-15107-y

Available from: 2016-04-22 Created: 2016-04-22 Last updated: 2017-11-30
Singh, B. P., Erni, W., Keshelashvili, I., Krusche, B., Steinacher, M., Liu, B., . . . Semenov-Tian-Shansky, K. (2015). Experimental access to Transition Distribution Amplitudes with the PANDA experiment at FAIR. European Physical Journal A, 51(8), Article ID 107.
Open this publication in new window or tab >>Experimental access to Transition Distribution Amplitudes with the PANDA experiment at FAIR
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2015 (English)In: European Physical Journal A, ISSN 1434-6001, E-ISSN 1434-601X, Vol. 51, no 8, article id 107Article in journal (Refereed) Published
Abstract [en]

Baryon-to-meson Transition Distribution Amplitudes (TDAs) encoding valuable new information on hadron structure appear as building blocks in the collinear factorized description for several types of hard exclusive reactions. In this paper, we address the possibility of accessing nucleon-to-pion (pi N) TDAs from (p) over barp -> e(+)e(-)pi(0) reaction with the future PANDA detector at the FAIR facility. At high center-of-mass energy and high invariant mass squared of the lepton pair q(2), the amplitude of the signal channel (p) over barp -> e(+)e(-)pi(0) admits a QCD factorized description in terms of pi N TDAs and nucleon Distribution Amplitudes (DAs) in the forward aid backward kinematic regimes. Assuming the validity of this factorized description, we perform feasibility studies for measuring (p) over barp -> e(+)e(-)pi(0) with the PANDA detector. Detailed simulations on signal reconstruction efficiency as well as on rejection of the most severe background channel, i.e. (p) over barp -> pi(+)pi(-)pi(0) were performed for the center-of-mass energy squared s = 5 GeV2 and s = 10 GeV2, in the kinematic regions 3.0 < q(2) < 4.3 GeV2 and 5 < q(2) < 9 GeV2, respectively, with a neutral pion scattered in the forward or backward cone vertical bar cos theta(pi 0)vertical bar > 0.5 in the proton-antiproton center-of-mass frame. Results of the simulation show that the particle identification capabilities of the PANDA detector will allow to achieve a background rejection factor of 5 . 10(7) (1 . 10(7)) at low (high) q(2) for s = 5 GeV2, and of 1 . 10(8) (6 . 10(6)) at low (high) q(2) for s = 10 GeV2, while keeping the signal reconstruction efficiency at around 40%. At both energies, a clean lepton signal can be reconstructed with the expected statistics corresponding to 2 of integrated luminosity. The cross sections obtained from the simulations are used to show that a test of QCD collinear factorization can be done at the lowest order by measuring scaling laws and angular distributions. The future measurement of the signal channel cross section with PANDA will provide a new test of the perturbative QCD description of a novel class of hard exclusive reactions and will open the possibility of experimentally accessing pi N TDAs.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-262977 (URN)10.1140/epja/i2015-15107-y (DOI)000360439700001 ()
Funder
Swedish Research CouncilEU, FP7, Seventh Framework Programme
Available from: 2015-09-23 Created: 2015-09-23 Last updated: 2017-12-01Bibliographically approved
Anastasi, A., Babusci, D., Bencivenni, G., Berlowski, M., Bloise, C., Bossi, F., . . . Wolke, M. (2015). Limit on the production of a low-mass vector boson in e(+)e(-) -> U gamma, U -> e(+)e(-) with the KLOE experiment. Physics Letters B, 750, 633-637
Open this publication in new window or tab >>Limit on the production of a low-mass vector boson in e(+)e(-) -> U gamma, U -> e(+)e(-) with the KLOE experiment
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2015 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 750, p. 633-637Article in journal (Refereed) Published
Abstract [en]

The existence of a new force beyond the Standard Model is compelling because it could explain several striking astrophysical observations which fail standard interpretations. We searched for the light vector mediator of this dark force, the U boson, with the KLOE detector at the DA Phi NE e(+)e(-) collider. Using an integrated luminosity of 1.54 fb(-1), we studied the process e(+)e(-) -> U gamma, with U -> e(+)e(-), using radiative return to search for a resonant peak in the dielectron invariant-mass distribution. We did not find evidence for a signal, and set a 90% CL upper limit on the mixing strength between the Standard Model photon and the dark photon, epsilon(2), at 10(-6)-10(-4) in the 5-520 MeV/c(2) mass range.

Keywords
Dark matter, Dark forces, Dark photon, U boson, A '
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:uu:diva-270452 (URN)10.1016/j.physletb.2015.10.003 (DOI)000364250600095 ()
Available from: 2016-01-19 Created: 2015-12-28 Last updated: 2017-11-30Bibliographically approved
Caldeira Balkeståhl, L. (2015). Measurement of the Dalitz Plot Distribution for η→π+π−π0 with KLOE. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Measurement of the Dalitz Plot Distribution for η→π+ππ0 with KLOE
2015 (English)Doctoral thesis, monograph (Other academic)
Abstract [en]

The mechanism of the isospin violating η→π+ππ0 decay is studied in a high precision experiment using a Dalitz plot analysis. The process is sensitive to the difference between up and down quark masses. The measurement provides an important input for the determination of the light quark masses and for the theoretical description of the low energy strong interactions.

The measurement was carried out between 2004 and 2005 using the KLOE detector at the DAΦNE e+e collider located in Frascati, Italy. The data was collected at a center of mass energy corresponding to the φ-meson peak (1019.5 MeV) with an integrated luminosity of 1.6 fb−1. The source of the η-mesons is the radiative decay of the φ-meson: e+e→φ→ηγ, resulting in the world’s largest data sample of about 4.7·106 η→π+ππ0 decay events.

In this thesis, the KLOE Monte Carlo simulation and reconstruction programs are used to optimize the background rejection cuts and to evaluate the signal efficiency. The background contamination in the final data sample is below 1%. The data sample is used to construct the Dalitz plot distribution in the normalized dimensionless variables X and Y. The distribution is parametrized by determining the coefficients of the third order polynomial in the X and Y variables (so called Dalitz plot parameters). The statistical accuracy of the extracted parameters is two times better than any of the previous measurements. In particular the contribution of the X2Y term is found to be different from zero with a significance of approximately 3σ. The systematic effects are studied and found to be of the same size as the statistical uncertainty. The contribution of the terms related to charge conjugation violation (odd powers of the X variable) and the measured charge asymmetries are consistent with zero.

The background subtracted and acceptance corrected bin contents of the Dalitz plot distribution are provided to facilitate direct comparison with other experiments and with theoretical calculations.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. p. 146
Series
Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-2516 ; 118
Keywords
Hadron physics, Quark masses, Hadronic decays, Light mesons, Meson-meson interactions
National Category
Subatomic Physics
Research subject
Physics with specialization in Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-266871 (URN)978-91-554-9427-8 (ISBN)
Public defence
2016-01-22, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2015-12-18 Created: 2015-11-12 Last updated: 2016-01-14
Bremer, D., Caldeira Balkeståhl, L., Calén, H., Fransson, K., Johansson, T., Kupsc, A., . . . Zmeskal, J. (2015). Performance of prototypes for the PANDA barrel EMC. Paper presented at 16th Int. Conf. on Calorimetry in High Energy Physics (CALOR 2014), Giessen Germany, 6-11 April, 2014. Journal of Physics, Conference Series, 587(1), Article ID 012052.
Open this publication in new window or tab >>Performance of prototypes for the PANDA barrel EMC
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2015 (English)In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 587, no 1, article id 012052Article in journal (Refereed) Published
Abstract [en]

The PANDA experiment will be part of the future Facility for Antiproton and Ion Research (FAIR) and aims for the study of strong interaction within the charm sector via antiproton proton collisions up to antiproton momenta of 15 GeV/c. Reflecting the variety of the physics program the PANDA detector is designed as a multi-purpose detector able to perform tracking, calorimetry and particle identification with nearly complete coverage of the solid angle. The Electromagnetic Calorimeter (EMC) contained inside its Target Spectrometer is based on cooled PbWO(4) scintillator crystals. In order to ensure an excellent performance throughout the large dynamic range of photon/electron energies ranging from a few MeV up to 15 GeV an extensive prototyping phase is mandatory. This contribution describes the measured response of the EMC barrel part prototype PROTO60 at the largest design energy to secondary beams provided by the SPS at CERN. In addition to PROTO60 a tracking station was deployed, providing precise position information of the 15 GeV/c positrons. For calibration purposes a 150 GeV/c muon beam and cosmic radiation, in combination with estimations from GEANT4 simulations were used. The obtained performance concerning energy, position and time information is presented.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-286776 (URN)10.1088/1742-6596/587/1/012052 (DOI)
Conference
16th Int. Conf. on Calorimetry in High Energy Physics (CALOR 2014), Giessen Germany, 6-11 April, 2014
Note

PANDA Collaboration, for complete list of authors see http://dx.doi.org/10.1140/epja/i2015-15107-y

Available from: 2016-04-21 Created: 2016-04-21 Last updated: 2017-11-30
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