Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSearch for the Chiral Magnetic Effect with Isobar Collisions at $sqrt{s_{NN}}$ = 200 GeV by the STAR Collaboration at RHIC
بحث عن تأثير المغناطيس الكيرالي مع الاصطدامات الإيزوبار في $sqrt{s_{NN}}$ = 200 جيجا فولت من قبل مشاركة ستار في ريهيك
678
0
0.0
(
0
)
Ask ChatGPT about the research
توقع تأثير المغناطيس الكيرالي (CME) أن يحدث كنتيجة من انتهاك محلي للتناسقيات $cal P$ و $cal CP$ للتفاعل القوي في الوسط المحيط بمجال كهربائي قوي الذي ينشأ في تصادمات الذرات الثقيلة الانحرافية. يتمثل التظهر التجريبي لCME في فصل الذرات المشحونة بطرفين مثبت وسالب على اتجاه المجال المغناطيسي. لم تظهر التجارب السابقة للمؤشرات المعرضة لCME الاستنتاجات الصحيحة بسبب المساهمات الخلفية الكبيرة. للسيطرة على تأثير الإشارات والخلفيات، أجرت التعاونية النجمية (STAR) تحليلاً مخفياً لعينة كبيرة من التصادمات الثنائية تقريباً بقدر 3.8 مليار من $^{96}_{44}$Ru+$^{96}_{44}$Ru و $^{96}_{40}$Zr+$^{96}_{40}$Zr في $sqrt{s_{rm NN}}=200$ GeV. قبل التحليل المخفي، يتم تعريف إشارات CME كزيادة ملحوظة في المؤشرات المعرضة لCME في التصادمات Ru+Ru على تلك التصادمات Zr+Zr بسبب المجال المغناطيسي الأكبر في الأولى. وتحقق الدقة حتى 0.4٪ في كميات المؤشرات المتعلقة بين النظامين الثنائين المتشابهين. ويشير الاختلافات الملحوظة في كميات التصادمات والأوزان الحركية في المركزية المتطابقة إلى أن كمية الخلفية المعرضة لCME هي مختلفة بين الجنسين. لم يتم الكشف عن إشارة CME تلبي المعايير المحددة مسبقاً في التصادمات الثنائية في هذا التحليل المخفي.
The chiral magnetic effect (CME) is predicted to occur as a consequence of a local violation of $cal P$ and $cal CP$ symmetries of the strong interaction amidst a strong electro-magnetic field generated in relativistic heavy-ion collisions. Experimental manifestation of the CME involves a separation of positively and negatively charged hadrons along the direction of the magnetic field. Previous measurements of the CME-sensitive charge-separation observables remain inconclusive because of large background contributions. In order to better control the influence of signal and backgrounds, the STAR Collaboration performed a blind analysis of a large data sample of approximately 3.8 billion isobar collisions of $^{96}_{44}$Ru+$^{96}_{44}$Ru and $^{96}_{40}$Zr+$^{96}_{40}$Zr at $sqrt{s_{rm NN}}=200$ GeV. Prior to the blind analysis, the CME signatures are predefined as a significant excess of the CME-sensitive observables in Ru+Ru collisions over those in Zr+Zr collisions, owing to a larger magnetic field in the former. A precision down to 0.4% is achieved, as anticipated, in the relative magnitudes of the pertinent observables between the two isobar systems. Observed differences in the multiplicity and flow harmonics at the matching centrality indicate that the magnitude of the CME background is different between the two species. No CME signature that satisfies the predefined criteria has been observed in isobar collisions in this blind analysis.
rate research
Read More
The Multi-Phase Transport model, AMPT, and the Anomalous Viscous Fluid Dynamics model, AVFD, are used to assess a possible chiral-magnetically-driven charge separation ($Delta S$) recently measured with the ${R_{Psi_2}(Delta S)}$ correlator in Au+Au collisions at $sqrt{s_{mathrm{NN}}}=200$ GeV. The Comparison of the experimental and simulated ${R_{Psi_2}(Delta S)}$ distributions indicates that background-driven charge separation is insufficient to account for the measurements. The AVFD model calculations, which explicitly account for CME-driven anomalous transport in the presence of background, indicate a CME signal quantified by the $P$-odd Fourier dipole coefficient ${a_1}approx 0.5%$ in mid-central collisions. A similar evaluation for the $Deltagamma$ correlator suggests that only a small fraction of this signal ($f_{rm CME}=Deltagamma_{rm CME}/Deltagamma approx 25%$) is measurable with this correlator in the same collisions. The related prediction for signal detection in isobaric collisions of Ru+Ru and Zr+Zr are also presented.
The chiral magnetic effect (CME) refers to charge separation along a strong magnetic field due to imbalanced chirality of quarks in local parity and charge-parity violating domains in quantum chromodynamics. The experimental measurement of the charge separation is made difficult by the presence of a major background from elliptic azimuthal anisotropy. This background and the CME signal have different sensitivities to the spectator and participant planes, and could thus be determined by measurements with respect to these planes. We report such measurements in Au+Au collisions at a nucleon-nucleon center-of-mass energy of 200 GeV at the Relativistic Heavy-Ion Collider. It is found that the charge separation, with the flow background removed, is consistent with zero in peripheral (large impact parameter) collisions. Some indication of finite CME signals is seen with a significance of 1--3 standard deviations in mid-central (intermediate impact parameter) collisions. Significant residual background effects may, however, still be present.
Quark interactions with topological gluon configurations can induce local chirality imbalance and parity violation in quantum chromodynamics, which can lead to the chiral magnetic effect (CME) -- an electric charge separation along the strong magnetic field in relativistic heavy-ion collisions. The CME-sensitive azimuthal correlator observable ($Deltagamma$) is contaminated by background arising, in part, from resonance decays coupled with elliptic anisotropy ($v_{2}$). We report here the first differential measurements of the correlator as a function of the pair invariant mass ($m_{rm inv}$) in 20-50% centrality Au+Au collisions at $sqrt{s_{_{rm NN}}}$= 200 GeV by the STAR experiment at RHIC. Strong resonance background contributions to $Deltagamma$ are observed. At large $m_{rm inv}$ where this background is significantly reduced, the $Deltagamma$ value is found to be also significantly smaller. An event shape engineering technique is deployed to determine the $v_{2}$ background shape as a function of $m_{rm inv}$. A $v_{2}$-independent signal, possibly indicating a $m_{rm inv}$-integrated CME contribution, is extracted to be $Deltagamma_{rm signal}$ = (0.03 $pm$ 0.06 $pm$ 0.08) $times10^{-4}$, or $(2pm4pm5)%$ of the inclusive $Deltagamma(m_{rm inv}>0.4$ GeV/$c^2$)$=(1.58 pm 0.02 pm 0.02) times10^{-4}$. This presents an upper limit of $0.23times10^{-4}$, or $15%$ of the inclusive result at $95%$ confidence level.
Measurements of three-dimensional correlation functions of like-sign low transverse momentum kaon pairs from Au+Au collisions at top RHIC energy $sqrt s_{NN}$=200 GeV are presented. The extracted kaon source function is narrower than the pion one and does not have the long tail along the pair transverse momentum direction. This indicates a much smaller role of long-lived resonance decays and/or of the emission duration on kaon emission. Three-dimensional Gaussian shape of the kaon source function can be adequately reproduced by Therminator simulations with resonance contributions taken into account. Comparison to pion data at the same energy reveals that the kaon Gaussian radii in the outward and sideward directions scale with the transverse mass $m_T$. In the longitudinal direction, unlike at lower SPS energies, the Gaussian radii do not seem to follow the exact $m_T$ scaling between kaons and pions.
We report on the measurements of production of various charmed hadrons in Au+Au collisions at $sqrt{s_{rm{NN}}}$ = 200 GeV (including $D^{0}(overline{D^{0}})$ and $Lambda_{c}^{pm}$) obtained via topological reconstruction, utilizing the Heavy Flavor Tracker at STAR. Precise results on the $D^{0}$ yields from the 2014 data are reported for a wide transverse momentum range down to 0 in various centrality bins. With the high-statistics data collected in 2014 and 2016, and the usage of a supervised machine learning algorithm for signal-to-background separation, the first measurement of the centrality and transverse momentum dependences of $Lambda_{c}^{pm}$ production is shown. Finally, the total charm quark cross section extracted from these measurements in Au+Au collisions at $sqrt{s_{rm{NN}}}$ = 200 GeV is presented.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
